Clinical Computer Tomography Head and ITunk

Edited by A. Baert . L. J eanmart . A. Wackenheim

With 414 Figures

Springer-Verlag Berlin Heidelberg New York 1978

A. BAERT, Professor van Radiologie, Diensthoofd, Radiodiagnose, Universitaire Klinieken, Capucienen voer, B-3000 Leuven '7.~ . L. JEANMART, Professeur de Radiologie, Chef du service de Radiologie, Institut J. Bordet, 3, rue Heger Bordet, B 1000 Bruxelles .-" J

A. WACKENHEIM, Professeur agrege de Radioiogie, Chef du service de Neuroradiologie et de Radiopediatrie, C.R.U. de Strasbourg, 1, place de l'Ropital, F-67005 Strasbourg­Cedex

ISBN-13: 978-3-540-08458-7 DOl: 10.1007/978-3-642-81182-1

e-ISBN-13: 978-3-642-81182-1

Library of Congress Cataloging in Publication Data. Main entry under title: Clinical computer tomography, head and trunk. Papers presented at a meeting organized by College d'enseignement post-universitaire de radiologie and held in Luxembourg, March 1977. Bibliography: p. Includes index. 1. Tomography--Congresses. 1. Baert, A., 1931-II. Jeanmart, L., 1929-, III. Wackenheim, Auguste. IV. College d'enseignement post-universitaire de radiologie. RC78.7.T6C54. 617'. 51'07572. 77-14224. This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically those of translation, reprinting, re-use of illustrations, broadcasting, reproduction by photocopying machine or similar means, and storage in data banks. Under § 54 of the German Copyright law, where copies are made for other than private use, a fee is payable to the publisher, the amount of the fee to be determined by agreement with the publisher. © by Springer-Verlag Berlin Heidelberg 1978.

The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.

Foreword

In this book are published papers presented at the first meeting about tomodensito­metry (Computer Tomography) which the CEPUR organized in Luxembourg in March 1977.

CEPUR (College d'enseignement post-universitaire de Radiologie) is an international medical association having as its main aim the promotion of courses in advanced radiology. Several sections deal with the subspecializations, one of which is Com­puter Tomography.

Thanks to the fruitful cooperation of several University Hospitals (Ancona, Leuven, Montpellier, Bruxelles, Strasbourg), the two-day meeting organized by Dr. Capesius in Luxembourg covered a certain number of aspects of clinical tomodensitometry in the brain as well as in the trunk.

We hope that this volume will be the first of a series dealing with the actual problems in clinical radiology.

Leuven/Bruxelles/Strasbourg A. BAERT L. JEANMART A. WACKENHEIM

Contents

I. Introduction to the Technology of Computer Tomography

K. Ungerer. With 18 Figures ... 2

II. Head

Sellar Region: Normal and Pathologic Conditions. U. Salvolini, F. Menichelli, and U. Pasquini. With 40 Figures ...... 14

Empty Sella and Pituitary Gland. J.L. Dietemann and A. Wackenheim. Wi th 3 Figures . • . . • . •. •.... • . ., 38

Midline Lesions. D. Baleriaux-Waha, L.L. Mortelmans, M. Dupont, and L. Jeanmart. With 17 Figures .......•.. 39

Ventriculocisternal Pathology in Children. D. Touitou. With 9 Figures . . . . . • . . • . . . . . . . .. ....... 47

Endocranial Calcifications. J.H. Vandresse, G. Cornelis, and A. Rousseau. With 20 Figures • . . . . . . . . . . . . . . . . .. 53

Area of Maximal Density in Extracerebral Tumors. J.C. Dosch. With 16 Figures .........•.... , ..... 59

Tumoral Masses of the Posterior Fossa. B. Staelens, Y. Palmers, A.L. Baert, and J.-L. Termote. With 16 Figures . . . . .. 65

Cerebellopontine Expansive Lesions. U. Salvolini, F. Menichelli, and U. Pasquini. With 35 Figures ...... . . . . 79

The Cervical Medullar Canal and its Content. P. Mancs and W. van Damme. With 14 Figures . . . . 104

Cerebral Ischemia. Y. 'Palmers, B. Staelens, A.L. Baert, and L. Termote. With 19 Figures . . . . 113

Cerebral Metastases. J.C. Dosch. With 8 Figures 128

Inflammatory Diseases of the Brain. M.G. Dupont, L.L. Mortelmans, D. Baleriaux-Waha, A. Bollaert, and L. Jeanmart. With 10 Figures 131

Epidermoid Cyst. A. Rousseau, G. Cornelis, and J.H. Vandresse. With 2 Figures . . . • . . . . • . . 139

Meningiomas en Plaque. B. Bittighoffer. With 4 Figures 142

Neuroophthalmology. L.L. Mortelmans, D. Baleriaux-Waha, M.G. Dupont, L. Jeanmart, and R. Potvliege. With 18 Figures .. 147

Arterial and Arteriovenous Malformations. J.C. Dosch. With 10 Figures . . . . . . . . . . . . . . . . . . . . . . . • . . . . . 156

VIII

III. Trunk

Chest. M. Osteaux, L. Jeanrnart, J. Struyven, and R. Huvenne. With 12Figures .......•...•.... . ...... 162

Liver. M. Osteaux, J. Struyven, R. Huvenne, and L. Jeanmart. With 17 Figures . • .. ....•.... • . . . • . . . 169

Liver and Pancreas. J.L. Lamarque, J.M. Bruel, R. Dondelinger, and B. Vendrell. With 14 Figures ••..•... 185

Pancreatic Disease. Y. Coenen, G. Marchal, E. Ponette, A.L. Baert, and J. Pringot. With 25 Figures. . . . . •. .••.. . 197

Kidneys. J. Struyven, M. Osteaux, R. Huvenne, and L. Jeanmart. With 24 Figures . • . .• ..... . .... 213

Retroperitoneal Region. G. Marchal, Y. Coenen, and A.L. Baert. With 25 Figures . . . . .. .•...• •... 221

Pelvis. G. Marchal, Y. Coenen, and A.L. Baert. With 27 Figures 239

Abdominal Computer Tomography and Contrast Media. R. Huvenne, A. Grivegnee, J. Struyven, M. Osteaux, L. Jeanmart, and A. Bollaert. With 11 Figures ..........•..•..•..•••... 253

Subject Index •......................... 259

Contributors

D. Baleriaux-Waha Premiere assistante Institut Bordet 3, rue Heger-Bordet 1000 Bruxelles (Belgique)

B. Bittighoffer Attache des Hopitaux Service de Neuroradiologie et de Radiopediatrie C.H.U. de Strasbourg 1, Place de l'Hopital 67005 Strasbourg-Cedex (France)

A. Bollaert Professeur de Radiologie Hopital St Pierre rue Haute 1000 Bruxelles (Belgique)

J.M. Bruel Service de Radiologie-Cliniques St. Eloi­C.H.U. 34000 Montpellier (France)

Y. Coenen Resident Universitaire Klinieken K.U.L. Capucienen voer 3000 Leuven (Belgie)

G. Cornelis Professeur de Neuroradiologie Universite Catholique de Louvain Clinique St Luc 10, avenue Hippocrate 1200 Bruxelles (Belgique)

J.L. Dietemann Interne des hopitaux de Strasbourg Service de Neuroradiologie et de Radio­pediatrie C.H.U. de Strasbourg 1, Place de l'Hopital 67005 Strasbourg-Cedex (France)

R. Dondelinger Attache a titre etranger Service de Radiologie-Cliniques St. Eloi­C.H.U. 34000 Montpellier (France)

J.C. Dosch Attache des hopitaux Service de Neuroradiologie et de Radio­pediatrie C.H.U. de Strasbourg 1, Place de l'Hopital 67005 Strasbourg Cedex (France)

M.G. Dupont Assistant Service de Radiologie Hopital St Pierre rue Haute 1000 Bruxelles (Belgique)

A. Grivegnee Assistant Hopital St Pierre rue Haute 1000 Bruxelles (Belgique)

R. Huvenne Assistant Hopital St Pierre rue Haute 1000 Bruxelles (Belgique)

J.L. Lamarque Professeur de Radiologie Service de Radiologie-Cliniques St. Eloi­C.H.U. 34000 Montpellier (France)

P. Mancs Attache des hopitaux Service de Neuroradiologie et de Radio­pediatrie C.H.U. de Strasbourg 1, Place de l'Hopital 67005 Strasbourg Cedex (France)

G. Marchal Adjunkt-Kliniek Hoofd Universitaire Klinieken K.U.L. Capucienen voer 3000 Leuven (Belgie)

F. Menichelli Ajusto Servicio di Radiologia (neuroradiologia)

x

49, Corso Stamira 60100 Ancona (Italie)

L.L. Mortelmans Eerstaanwezend assistent Universitaire Ziekenhuis Brugman-V.U.B. Place· Van Gehuchten 1020 Brussel (Belgie)

M. Osteaux Premier assistant Institut Bordet 3, rue Heger-Bordet 1000 Bruxelles (Belgique)

Y. Palmers Resident Universitaire Klinieken K.U.L. Capucienen voer 3000 Leuven (Belgie)

U. Pasquini Ajusto Servicio di Radiologia (neuroradiologia) 49, Corso Stamira 60100 Ancona (Italie)

E. Ponette Adjunkt-Kliniek Hoofd-Docent Universitaire Klinieken K.U.L. Capucienen voer 3000 Leuven (Belgie)

R. Potvliege Professeur de Radiologie Hopital Brugmann Place Van Gehuchten 1020 Bruxelles (Belgique)

J. Pringot Charge de cours Universite Catholique de Louvain Clinique St Luc 10, avenue Hippocrate 1200 Bruxelles (Belgique)

A. Rousseau Assistant Service de Neuroradiologie Universite Catholique de Louvain Clinique St Luc 10, avenue Hippocrate 1200 Bruxelles (Belgique)

U. Salvolini Ajusto Servicio di Radiologia (neuroradiologia) 49, Corso Stamira 60100 Ancona (Italie)

B. Staelens Resident Universitaire Klinieken K.U.L. Capucienen voer 3000 Leuven (Belgie)

J. Struyven Adjoint Hopital Brugmann Place Van Gehuchten 1020 Bruxelles (Belgique)

L. Termote Resident Universitaire Klinieken K.U.L. Capucienen voer 3000 Leuven (Belgie)

D. Touitou Chef de Clinique Assistant Service de Neuroradiologie et de Radio­pediatrie C.H.U. de Strasbourg 1, Place de l'Hopital 67005 Strasbourg Cedex (France)

K. Ungerer Siemens D8520 Erlangen (Deutschland)

W. Van Danune Attache des Hopitaux Service de Neuroradiologie et de Radio­pediatrie C.H.U. de Strasbourg 1, Place de l'Hopital 67005 Strasbourg Cedex (France)

B. Vandrell Attache des hopitaux Service de Radiologie-Cliniques St. Eloi-C.H.U. 34000 Montpellier (France)

J.H. Vandresse Resident Service de Neuroradiologie Universite Catholique de Louvain Clinique St Luc 10, avenue Hippocrate 1200 Bruxelles (Belgique)

I. Introduction to the Technology of Computer Tomography

Introduction to the Technology of Computer Tomography K. Ungerer

Why is computer Tomography Needed?

Conventional radiology encompasses the skeleton and, with the help of contrast medium, the intestinal tract and the vascular system, with some exceptions. In these areas, radiology today has attained a high degree of reliability and information quality.

However, human beings are composed predominantly of tissue, i.e., muscles, glands and organs, so-called soft tissue. The absorption of X-radiation by this soft tissue is approximately the same as that for water but does not vary so much, and therefore conventional radiology is not very successful in representing it. A visible contour on an X-ray film requires a certain absorption difference, which is not the case with soft tissues. To determine the soft tissue structures, one must abandon the relatively insensitive pictorial display for a pure measurement method which distinguishes between the various types of tissue by measuring their absorption of X-rays.

Since, however, the radiologist is accustomed to a pictorial display, he readily combines the measured values again into a picture. If one considers that a picture composed of only 100 vertical and 100 horizon­tal lines already contains 10,000 individual points, it is obvious that only a computer can carry out the image calculation. We are there­fore dealing with a device measuring X-ray absorption, which, with the help of a computer, produces an image from the gathered measurement data.

The Principle of Computer Tomography

A measuring device consisting of X-ray tube and scintillation detector (Fig.1) supplies only one discrete absorption value, which represents the sum of all the absorbers positioned in the radiation beam. However, if one moves the device and guides the measuring beam over the object, then one obtains a so-called measurement profile, which, with appropriate collimation is the profile of a section of the object. To produce a complete image, we need as many as possible of these profiles. By turn­ing the measuring device by a definite angle aftgr every transverse movement until a complete half revolution of 180 has been carried out, sufficient measured values are obtained to produce an image. The na­ture of the tomographic procedure along with the data processing of a computer have also given the method its name: Computer Axial Tomography, also abbreviated CAT, or for particular brevity it is named CT in the Anglo-American world.

Both X-ray tube and detector system turn about the object by a pre­cision drive, and according to the type of movement, translational, rotational or both, the various so-called generations of equipment are distinguished. The first CT-equipments (Fig.2) were mainly head units with a simple radiation geometry, the X-ray tube standing op­posite one detector, consisting of a scintillation crystal with photo­multiplier. The scanning was linear from different directions, each

3

a small angle apart, which also explains the relatively long recording time of about 5 minutes for a skull tomogram. Multidetector arrange­ments form the second generation in which the radiation beam emitted from the X-ray tube is split by a collimator (Fig.3) into several in­dividual rays, impinging on as many detectors. The detectors are in­clined to the center line, thus simulating a sequence of discrete angle settings. For this reason, the recording time is reduced - at least theoretically - in direct proportion to the number of detectors. Most of the systems offered today belong to this type of equipment, which has a shorter scanning time of about 15 seconds. The next generation of equipment has a fundamentally different radiation geometry. Called "fan-beam machines" (Fig.4) on account of the wide, fanning bundle of X-ray beams which cover the whole object, they possess a complex multiple detector system. Since the multiplicity of detectors cannot be realized in the form of scintillation crystal with photomultipliers for reasons of space, high-pressure ionization chambers are fitted on these machines, even image-intensifier arrays have also been known. A variant of this type of CT possesses station­ary radiation detector systems, arranged on a circle and only the X-ray tube moves, and only in a rotational manner. The recording time of fan-beam equipment is correspondingly short, in only about 5 se­conds. Today only a few examples of this so-called third generation exist, mainly as prototypes for technical and clinical trial.

The Historical Development

The computer tomograph was developed over many years by the English physicist, Dr. Hounsfield of the EMI company and was made public for the first time in 1972. Although Dr. Hounsfield based his work and thought such as, e.g., FRANK (1938), CORMACK (1963/64) and OLDENDORF (1963), and although the mathematic basis of image reconstruction had already been researched by nuclear physicists and astronomers, the merit nevertheless belongs to him for recognizing the applicability of the measuring method with only very limited spatial resolution but an excellent contrast discriminating capability in investigations on human soft tissue. Dr. Hounsfield was lucky to find a partner for the medical aspect in Dr. Ambrose, who not only recognized the value of the examination method, but also helped in the breakthrough with very painstaking experiments on the method's application to the head. Their work released a revolution in neuroradiology.

The first head units were still quite simple and necessitated a water bag for positioning the head. All the more surpr~s~ng was the report of the American physicist, Dr. Ledley of Georgetown University, USA, who published CT-pictures of the body trunk taken without water compensating bag. Indeed, there was later some doubt as to whether these first images, the quality of which must have caused amazement due to the long scanning time of 8 minutes, had not afterall been made on a corpse. Despite these objections, Dr. Ledley and his working group with Dr. Di Chiro retain the merit on the medical side of having made the first images of the body trunk. Their equipment, which they call the ACTA-Scanner, is built today under the management of the Pfizer company. With increasing technical development, new equipment quickly came onto the market, permitting new examinations. As pioneers in computer tomography on the whole body in this initial period I would like to name Dr. Alfidi from the Cleveland Clinic in the USA and Dr. Kreel from England.

4

Since CT is a method of measuring, a measuring scale is also needed. The absorption coefficient with which the physicist is used to work­ing is, however, a rather unwieldy, many digit number, which is not defined for the polychromatic radiation spectrum which the X-ray tube supplies. Recognizing this, Dr. Hounsfield suggested a relative scale (Fig.5) based on the absorption of water, which has a similar density to that of soft tissue. On this scale water is assigned the value 0, twofold higher absorption, corresponding to a rather dense bone, is then designated +1000 and a smaller absorption, approximating that of air, is designated -1000. The critical range for soft tissue diagnosis including fat and denser tissue extends from about -200 to +200.

However, the contrast gain is so high that all density values can no longer be displayed at the same time. The range of interest must be selected, since the image signal is already in the form of electri­cal pulses, by an electronic window (Fig.G). By this means, the mini­mum and maximum densities which are of immediate interest are deter­mined and this range is expanded over the whole image. The window set­tings, sometimes even the whole associated absorption scale, are usu­ally shown at the side of the tomogram.

The CT-System

Although the requirements of a whole-body CT-unit differ considerably from those of a head system, both machines have so much in common that one can first of all distinguish the following elements: (Fig.7)

The X-ray power supply and possibly a cooling assembly, The computer, An operator's terminal, possibly combined with a display terminal or a separate oneline or offline display terminal, The scanning unit with the patient table (Fig.8).

Inside the scanner, the X-ray tube moves with the sophisticated col­limator system and the radiation detectors. Despite the considerable masses which are accelerated and then stopped again, some machines are so well counterbalanced that the scanner is supported on only one axis and thus can also be tilted, an advantage when scanning organs which are not perpendicular to the body axis, e.g., the pancreas. X-ray exposure takes place in a tunnel-like opening in which the position of the section is indicated by a light-beam indicator. The scanning aperture and the gantry of course differ in size in head and whole-body units.

The tables are likewise different. The whole-body unit needs two of these, one in front of and one behind the scanner, so that the patient can be appropriately positioned. A conveyor belt is usually built in to facilitate guiding the patient into the scanner. The advancement of the conveyor, on some system by separately programmed remote con­trol, can also be used for successive sections. The head units are provided with a table or positioning chair. Because of the rather long recording times, good positioning in a relaxed state is of crucial importance. In some head units the rear side of the scanning aperture has been left open, so that extremities or even infants can be ex­amined

The first CT-units and stationary anode tubes required water cooling due to the long operating time. This principle is still found in the CT-machines of the second generation, but of course rotation anode tubes are also used. The fan beam systems have to be operated with

5

high-output rotating anode tubes, and therefore the X-ray generator associated with them must be powerful. A particularly good stabiliza­tion of X-ray current and tube voltage is important here, however, because the calibration of the CT-system applies only for these values, and every deviation reduces the contrast resolution.

From the tube and generator data, it is easy to conclude that the dose applied to the patient is rather high, but this is not in fact the case (Fig.9). Since the dosage lies in the same range of 0.3 - 1 rad as the values used for conventional planigraphs, one must assure that only a small part of the skin surface is irradiated due to the very strict collimation.

An essential component of the system is the computer. In actuality, however, since a sole computer would be too slow for the scheduled image calculation, a complete computer system (Fig.10) is installed in which smaller peripheral units are allocated prescribed tasks, e.g., the conversion of the analogue detector signal into the digital form required for the computer, the actual image calculation, and finally the reconversion of the machine data into an image, often even direct­ly into a TV-picture. Most CT-systems today calculate an image accord­ing to the so-called convolution process, by which the representinq of a function, namely the measured values, is translated into another function corresponding to the image. The advantage of this process is the simultaneous calculation of the image and the measurement, i.e., the computing operation begins as soon as the first measured profile is available. A disadvantage of the convolution operation is the large number of mathematical operations which must be carried out in a short time keeping the image reconstruction more or less in step with the procedure, so that the image is available on conclusion of the measure­ment.

The central computing mechanism controls merely the operations, which are then carried out by the special small computers. With some CT­systems, this permits a partially simultaneous operation for individual functions, such as, e.g., replay of an image during the recording of another. For documentation the monitor image is normally photographed with built-in photo devices and cameras. The Polaroid procedure al­though still frequently used, is not highly recommended, because it partially wastes the careful processing of the image on the electronic side due to its narrow contrast reproduction. Closely connected with documentation is image filing. Since the image exists in the form of TV-signals anyway, there are numerous possibilities of storing the original measured values onto tapes, cassettes or disks and if neces­sary even printing them out.

Various Equipment Types

It has already been stressed that head and whole-body computer tomo­graphs are different. The differences are, however, not only external. A head system demands highest contrast resolution above all and then second, good spatial resolution. On the other hand, the whole-body scanner requires first, on account of organ movements, short scanning times, second, high spatial resolution and last, good contrast resolu­tion. This results in considerable differences also on the inside of the machine. Even the most modern head units are provided with multi­detector systems, while the whole-body system will be further devel­oped in the future in the direction of the fan beam. The interests and experiences of the large market leaders approximately parallel this development. EMI in the head sector and Ohio Nuclear in the whole­body equipment surpass all other firms so far.

6

Despite its considerable technical expenditure, a CT-system requires no more room and installation preparations than a large conventional X-ray system (Fig.11). The single exception is an air-conditioning system, which maintains constant temperature in the prese~ce of the machine's considerable heat production.

Statistics show a patient frequency of 12 - 18 persons per day, with the head units coming off slightly better because the number of tomo­grams is lower. The approximate value of the examination time is 20 -24 min/patient, sometimes somewhat longer, especially when contrast medium is administered.

Medical Examples

The two tomograms (Fig.12 and 13) via the density measurement of the white and grey cerebral matter show what small density differences (13 delta points) are reproduced with the CT, and not only optically but also quantitatively measured.

Figure 14 shows a section through the Orbita region with impressive display of the anatomy. The sphenoid sinus, cranial fossa, the orbit, with eyes and optic nerve, condyles, auditory ossicles and the muscles of the neck.

In Figure 15 the same orbit is shown magnified. While containing no more information, this picture CT, nevertheless, presents details such as the optic nerve which are subjectively richer in contrast. Good head CT-systems are recognized by the fact that the tomograms contain no artifacts, which can be caused by large density differences of closely neighbouring regions (dense bones, air or tissue).

In Figure 16 a section through the mediastinum is seen. The image, taken with a scan time of 18 seconds, shows the trachea, the oesoph­agus and some vessels quite clearly.

Figure 17 shows a section through the upper abdomen with good display of the liver and gallbladder, contrast medium in the left pole of the kidney and renal vein.

Another section through the abdominal region (Fig.18) shows a renal cyst with density measurement (7 delta points), pancreas, gallbladder and aorta surrounded by the peritoneum. These few examples give an impression of today's quality in computer tomography.

Future Prospects

It is naturally difficult, and moreover thankless, to make predictions in the midst of rapid technical and medical development of the CT. For this reason, only those prognoses which experiments have already shown to have some prospects of success will be considered.

The transverse section has particular significance in radiotherapy, since it is becoming the basis of therapy planning, thus replacing the simulator. For the surgeon and above all, the neurosurgeon, not only the axial sections but also projections from other angles are valuable for surgical treatment. When an appropriate patient positioning is not possible, whole-body machines are above all suitable for this on ac­count of the large aperture, the required view is determined by com­puter.

7

Another prospect is suggested by the fact that the absorption measure­ment contains separate terms for the photo-absorption and the Compton effect. If one examines a slice with two different radiation hardnes­ses, then, in principle, the absorption equation may be completely solved, and then a statement is made not only about the absorption at a particular part of the image but also about the atomic number and therefore the make-up of the tissue. This procedure returns to the origin of the CT, quantitative measurement.

As physicists, we cannot emphasize strongly enough that the basis of the CT is absorption measurement, and that the image is actually only a visual model. We can only hope that the medical profession does not forget, in its initial enthusiasm about extending radiology into the area of soft tissue diagnosis, that we have also renounced the quali­tative assessment of image shadows for the display of quantitative absorption values.

~ ---------------~ Fig.i. CT-principle, absorption measurement

Fig.2. CT-scanning principles

8

-------Ol~~r ....... 100

50 ZIIO

ANuIIIber +1000

o

-1000

Fig.3. CT-X-ray-beam collimation

Fig.4. CT-fan-beam prin­ciples

Fig.S. CT: Measurement scale with various ab­sorption values

+1000 +1000

+ 800 -

+ 600

+ 400 -

+ 200 -

0-

800

- 1000 - - 1000

Image prote •• or

X·Ray power supply

X·Ray (ontrols

Conlrol con.ol.

Fig.G. CT: Electronic window Fig.7. CT: components of a unit variation

~ ·Scan 50 FastScan 2 Typical Dosages in Rads

H£AO A

Fig.S. CT: Scanning unit with patient table

October 1976

BODY

A Siall ol :at ' Q

C)"~--'1' 0 '::':::':'

Body

Scan cl,cle r Scan time'

Slice Ihlck"e .. X· ,ayoutput 140 Ky. 35 me

42 em

20 sec 13mm

Scan P, I,. . I 1

( PMllllft.,t

r I

Cumul.tlv. Do •• f -IR. d.) A 6 r B 2 25 C 22 3 o 15

Fig.9. CT: Typical dosage measurement

" s.ec 13 mm

25cm l 140 Kv. 35 ma

7

2

15

1

2S

9

10

Fig.12

Fig.12. CT: Section

Fig.13. CT: Section

Fig.14. CT: Section

PDP 11 CU

Fig. 13

through upper skull;

through upper skull;

through Orbi ta region

Fig.l0. Computer structure

Fig.ll. CT: Installation drawing

Fig.14

density measurement of white matter

density measurement of grey matter

Fig.15. CT: Magnified Orbita region; distance measurement

Fig.17 Fig.18

Fig.17. CT: Section through upper abdomen showing liver, gallbladder, kidney, renal vein

11

Fig.18. CT: Section through abdomen showing renal cyst, pancreas, gallbladder, aorta

II. Head

Sellar Region: Normal and Pathologic Conditions u. Salvolini, F. Menichelli, and U. Pasquini

Introduction

computer tomography (CT) has gained a preeminent position in the neuroradiologic diagnosis of cranial and intracranial disease. Numerous authors have assessed its value and results in a large number of cases compared with other neuroradiologic investigations and in the light of its results and repercussions at clinical level. While its importance for intracranial diseases has remained generally unchanged, the value of CT in the sellar region was at first doubted, only later gaining ever more recognition.

The first users of CT (NEW et al. 1974; BAKER et al. 1974; AMBROSE 1974) feared that the high density of bone at the base of the skull and the low density of air in the sphenoidal sinus and ethmoidal cells would obscure the structures of the sellar region, rendering identifi­cation difficult even at suprasellar level. Similarly all researchers of this first period assessed the reliability of CT at para sellar level to be as low as 60% of cases handled (AMBROSE et al. 1975) and the rate of false negatives at the level of the suprasellar space to be around 40% (GREITZ 1975). Some (COLLARD and DUPONT 1975) ruled out CT for intrasellar but not for suprasellar diseases, despite the alleged difficulty of establishing the exact origin of a primary lesion of the sella with suprasellar growth of a primary lesion of the brain (FARNIER 1976); they concluded that the supra- and parasellar region should still be examined by pneumoencephalography-tomography with venography of the cavernous plexuses (NEW and SCOTT 1975), in view of the complexity of the anatomic structures in such a small space.

The opinions cited above reflected the technical situation in the early stage of CT, especially regarding its low spatial definition and the presence of calculus artifacts that caused low visibility of struc­tures near high differential absorption areas (zones adjacent to bone). Both hardware and software development on the one hand and increased diagnostic sensitivity on the other have led to a partial consider­ation of the concepts set forth above. As far back as 1975, GREPE pro­posed using contrast media to enhance the density of the parasellar subarachnoid space; its use intravenously led to a reassessment of the possibilities of diagnosing tumors. Von WILD et al. (1976) concluded that CT permitted both an early diagnosis of the extrasellar extent of adenomas as well as their subsequent follow-up without systematically resorting to pneumoencephalography (PEG). BECKER et al. (1976) included in CT the control of posttreatment recurrences or at any rate of un­excized remains, and REICH et al. (1976) considered screening for expanding suprasellar lesions feasible. STEINHOFF (1976), however, warned of the nonspecificity of increased density of parasellar mas-ses after intravenous contrast media and contended that clinical data (field changes, hormonal assays) were more useful for a differential diagnosis.

Other ways of enhancing CT reliability in the sellar region were tried. AMBROSE (1976) and DOP (1976) suggested that a semiaxial or frontal angulation was a more valid approach than a standard axial angulation used until then, while HAMMERSCHLAG et al. (1977) and LILIEQUIST (1976) showed that with a suitable technique both the

15

bone structures of the sellar region and, after contrast medium, the cavernous plexuses and internal carotids bilaterally were demonstrable, thereby visualizing the development of any intrasellar tumors not only at suprasellar but also at laterosellar level and in the direction of the sphenoid.

More recent appraisals (FAHLBUSCH et al. 1976~ NAIDICH et al. 1976) and a substantial revaluation of CT at parasellar and sellar level provided that certain indispensable technical requirements are com­plied with, e.g., complete immobilization of the patient's head, an adequate dosage of intravenous contrast, and thin or partly overlap­ping cuts. However, because dimensional limits for intrasellar lesions remain, DAVIS et al. (1976) consider that purely intrasellar adenomas are impossible to detect, although even FAHLBUSCH reports that AMBROSE (1976) had demonstrated a case of purely intrasellar disease. On the other hand, "empty sellas" are demonstrable (NAIDICH et al. 1976 report 5 cases), although the same authors contend that it is impossible to demonstrate microadenomas coexisting with "empty sella". The problem of diagnosing "empty sella" has been tackled in detail by BAJRAKTARI et al. (1977), using cisternal contrast investigations with CT and image reconstruction on orthogonal planes. They concluded that it was possible to diagnose with CT an intrasellar extension of subarachnoid space, provided that it was of a certain size. Their use of CT to de­monstrate a purely intrasellar tumor raised prospects of its demonstra­ting even microadenomas.

On the strength of the above mentioned reassessments, we set ourselves the task of assessing under present technical and methodologic con­ditions CT's actual contribution to the diagnosis of sellar and para­sellar diseases and in the light of our own experience.

Material and Method

Although experience covered over 6500 patients examined with an EMI­Brain Scanner Mark 1 during a 22 month period, it is not possible to estimate how many of these patients were investigated with special reference to the sellar or parasellar region~ however, this region was investigated by the following technique whenever it was clinically in­dicated, i.e., whenever one or more clinical features pointed to a disease of the region (field defects attributable to chiasmal lesion, altered hormonal assays, sellar changes demonstrable with preliminary plain X-rays of the skull, neuro-ophtalmologic diseases in general). The number of patients investigated with special reference to the sella turcica may be approximated from the information that about 20% of the patients were of neuro-ophtalmologic interest.

We had no standardized method of investigation but rather adjusted the technique to the clinical problem at hand. Nevertheless, we followed certain rules that we considered essential for obtaining a valid result in the sellar region.

a) Immobilization of the patient: the patient's cooperation was always sought as far as possible~ when this was not possible sedation was used, in rare cases, anesthesia. To help the patient maintain the desired position and to restrain the head in order to prevent even the slightest

16

involuntary movement, was added a chin-stop to the scanner; the com­bined action of this accessbry and the water-box kept the patient in position.

b) Angulation: for studying the sellar region an angulation parallel to the Reid line or the Frankfurt plane was systematically adopted; in some cases the scanning on a plane angled about 100 caudally (angle open ventrally) to this was repeated. In this way it was pos­sible to examine the sellar region in planes parallel to the upper district and to the floor, at the same time also obtaining information about the anterior or posterior clinoids on the same cut. In all cases the suprasellar region not only at this angulation but also at the standard angulation to the orbitomeatal line were examined too.

c) Cuts: 8 mm (nominal) cuts, overlapped partially, were consistently used; as a rule, the sellar region was studied by scanning a layer in­cluding the sphenoid and the floor of the sella, then a plane including the cavity, one containing the district above and finally one with the suprasellar region.

d) Processing of the Images: the scanning data were examined systemati­cally on the Diagnostic Display Console to obtain information both on the contents of the sella as well as on the bone of the base of the skull and on the paranasal air cavities.

e) Contrast studies: scanning was done before and after fast intra­venous injection of water soluble iodized contrast medium in a dosage of 2 cc/kg body wt. of a 65% solution of methylglucamine salt. If the investigation lasted over 20s, a further injection of contrast was given to maintain a high concentration of iodine in the blood.

Results - Discussion

The visualization of normal findings shows clearly that in the present state of spatial definition and density and with the algorithms avail­able insoluble problems no longer arise due to the high difference of absorption between continous structures (air-bone-brain) or because of fineness of detail. It is even possible to evaluate very small sellae, even with hyperpneumatization of the clinoids, and at the same time receive information on structures as small as the optic chiasm, which is almost consistently identifiable at the level of the aditus as an anteriorly open V-shaped image central to the space between the anterior and posterior clinoids.

The suprasellar and interpeduncular cisterns are interesting to study both in the special projection used and in the standard projection; in the latter, after administration of contrast medium, it is possible under normal conditions to obtain a complete image of the circle of Willis.

Once the cavernous plexuses are identified, an intravenous injection of contrast medium facilitates determining the lateral limits of the sellar cavity. At this phase it is possible to obtain both an image of the A1 segment of the anterior cerebral arteries and of the carotid siphons in a cut directly above the sella as well as an image of hypo­physial tissue in a partially "empty" sella (see DIETElifANN and WACKEN­HElM p. 38). Systematic study of the vascular structures and of the cisternal space (in particular of the suprasellar cistern and lamina terminalis) affords information on the intra- or extracerebral site of certain expanding lesions.

17

The empty sella is often identified in the field of pathology, although the empty sella in these cases seems to result from fairly large ex­tensions of the intrasellar arachnoid space, as BAJRAKTARI et al. (1977) rightly point out. In some patients exhibiting chiasmal and endocrine symptoms suggestive of "empty sella" combined with adenoma (or "micro­adenoma") a combination of empty sella and hyperdense nodules of fleshy tissue has been demonstrated after administering contrast medium. Indeed, even small adenomas still confined to the sella but occupying all or part of it have been visualized. However, the term "microadenoma" should be avoided since the dimensions of adenomas are clearly above microscopical level and, in all events, they certainly do fall within the group of pure intra sellar adenomas, exhibiting no signs of growth outside, which some workers have mistakenly called "microadenomas". In our view this term should be reserved for cases where CT fails to yield positive information but where indirect signs of a small sellar adenoma are present; in such cases the displacement of the floor detec­ted by plain X-rays at times has been confirmed although no tumor nodules have been demonstrated for sure.

In the case of adenomas tending to extrasellar growth or with clear extrasellar growth CT offers a wide range of diagnostic possibilities for showing clearly the limits and connections of the mass and supply­ing information on its consistency by differentiating solid from cystic or mixed masses. CT also supplies pathognomonic data in special cases, e.g., craniopharyngioma (irregular parietal calcifications, hypervascu­lar capsule and liquefied nucleus) or of chordoma (typical bone erosion with patches of hyperdensity after intravenous administration of contrast medium). In the field of parasellar diseases CT has long sup­plied information of unquestionable value; for example, diagnosis of the site of a foreign body and its constitution or, in the field of malformations, the simultaneous demonstration of bone and brain find­ings. In the case of extrasellar expanding lesions CT often supplies useful information on their connections with sellar and parasellar structures; the same applies to some arterial or arteriovenous mal­formations, although here size is critical for detection.

Concluding Remarks

In the light of the foregoing and weighing the results obtained, the value of CT even in a region as complex as the sellar and para sellar space should be reappraised. With the demonstration of even small intrasellar lesions it is possible to draft the following study pro­cedure for this region: first, a clinical study (with special reference to field defects and endocrine status); second, a basic radiologic study with tomography; third, CT carried out in accordance with the rules described and assessed critically; fourth, angiography, the value of which remains intact in practice. However, air studies with tomography and venography of the cavernous plexuses are resorted to only if the diagnosis is still uncertain. Only general guidelines, not specific rules are suggested, since obviously every individual patient must be examined in terms of a specific clinical query.

In summary, CT, although with inherent limits, is unquestionably impor­tant for the study of the sellar region, and the method should be re­fined as far as possible to utilize it to its utmost. Unfortunately there are no data on the results of scanning other planes orthogonal to the axial plane or of cisternography combined with CT. However, both possibilities are of great interest since they promise to increase the knowledge obtainable from such a valuable and relatively nontraumatic method as CT.

18

Bibliography

AMBROSE, J.: Computerized X-ray scanning of the brain. J. Neurosurg. 40, 679-695 (1974)

AMBROSE, J., GOODING, M.R., RICHARDSON, A.E.: An assessment of the accuracy of computerized transverse axial scanning (EMI-Scanner) in the diagnosis of intra­cranial tumour. A review of 366 patients. Brain 98, 569-582 (1975)

AMBROSE, J.: Personal Comunication, 1976. Citato da Fahlbusch BAJRAKTARI, X., BERGSTROM, M., BRISMAR, K., GOULATIA, R., GREITZ, T., GREPE, A.:

Diagnosis of intrasellar cisternal herniation (Empty sella) by computer assisted tomography. J. Comput. Assist. Tomogr. 1-, 105-116 (1977)

BAKER, H.: The impact of computed tomography on neuroradiologic practice. Radiology 116, 637-640 (1975)

BECKER, H., SCHAFER, M., KLOS, G.: Localization of recurrent brain tumours by means of computerized tomography. In: Cranial Computerized Tomography. Lanksch, W., Kazner, E. (eds.), Berlin-Heidelberg-New York: Springer 1976 pp. 143-150

COLLARD, M., DUPONT, H.P.: La tomographie axiale transverse computerisee par EMI­Scanner. Premier bilan apres 1000 observations. Ann. belge de Radiologie 58, 289-328 (1975)

DAVIS, K.R., TAVERAS, J.M., ROBERSON, G.H., ACKERMANN, R.H.: Some limitations of computed tomography in the diagnosis of neurological diseases. Am. J. Roentgenol. 127, 111-123 (1976)

OOP, A., CONSTANT, P., RENAUD-SALIS, J. L., CAILLE', J. M.: Interet de la tomodensi­tometrie en pathologie tumorale de la base du crane et du massif facial. J. Neuroradiol. lJ 193-214 (1976)

FAHLBUSCH, R., GRUMME, A., AULICH, A., WENDE, S., STEINHOFF, H., LANKSCH, W., KAZNER, E.: Suprasellar tumours in the CT Scan. In: Cranial Computerized Tomography.

Lanksch, W., Kazner, E. (eds.). Berlin-Heidelberg-New York: Springer 1976 pp. 114-127

FARNARIER, P., RAYBAUD, C., PALMIERI, P., MICHOTEY, P.: Etude tomographique des tumeurs cerebrales par tomographie axiale avec ordinateur. J. Neuroradiol. ~, 221-245 (1976)

GREITZ, T.: Computed Tomography for diagnosis of intracranial tumours compared with other neuroradiologic procedures. Acta. Radiol. (suppl.) 346, 14-20 (1975)

GREPE, A., GREITZ, T., NOREN, G.: Computer cisternography of extracerebral tumours using lumbar injection of water soluble contrast medium. Acta Radiol. (suppl.) 346, 51-62 (1975)

HAMMERSCHLAG, S.B., WOLPERT, S.M., CARTER, B.L.: Computed tomography of the skull base. J. Comput. Assist. Tomogr. ~, 75-80 (1977)

LILIEQUIST, B., FORSELL, A.: Computer tomography of the neurocranium. Acta Radiol. Diagnosis 12, 339-404 (1976)

NAIDICH, T.P., PINTO, R.S., KUSHNER, M.J., LIN, J.P., KRICHEFF, 1.1., LEEDS, N.E., CHASE, N.E.: Evaluation of sellar and parasellar masses by computed Tomography.

Radiology 120, 91-99 (1976) NEW, P.F., SCOTT, W.R., SCHNOR, J.A., DAVIS, K.R., TAVERAS, J.M.: Computerized

axial tomography with the EMI-Scanner. Radiology 110, 109-123 (1976) NEW, P.F.J., SCOTT, W.R.: Computed Tomography of the Brain and orbit (EMI-Scanning).

Baltimore: Williams & Wilkins Co. (1975) PAXTON, R., AMBROSE, J.: The EMI-Scanner. A brief review of the first 650 patients.

Brit. J. Radiol. iI, 530-565 (1974) REICH, N.E., ZELCH, J., ALFIDI, R.J., MEANY, T.F., DUCHESNEAU, P.M., WEINSTEIN, M.A.:

Computed Tomography in the detection of juxtasellar lesions. Radiology ~ 333-335 (1976)

STEINHOFF, H., AVILES, CH.: Contrast enhancement response of intracranial neoplasms Its validity for the differential diagnosis of tumours in CT. In: Cranial Com­puterized Tomography. W. Kazner, E. (eds.). Berlin-Heidelberg-New York: Springer 1976 pp. 151-161

STEINHOFF, H., LANGE, S.: Principles of contrast enhancement in computerized tomo­graphy. In: Cranial Computerized Tomography. Lanksch, W., Kazner, E. Berlin-Heidelberg-New York: Springer 1976

19

STEINHOFF, H., LANKSCH, W., FAHLBUSCH, R., KAZNER, K.: The use of computerized tomography (CT) in diagnosis of tumours in the suprasellar region. 5th Congress of the European Society of Neuroradiology. Geilo, 1975, abstr. 13.

VON WILD, K., GRAU, M., NEUBAUER, M., ALTHOFF, P.H.: The importance of cranial computerized tomography in diagnosis and continuous follow-up space-occupying lesions of the Sellar Region. In: Cranial Computerized Tomography. W. Kazner, E. (eds.). Berlin-Heidelberg-New York: Springer pp. 128-132 (1976)

Fig.1. Normal case. Note the possibilities afforded by using different windows: demonstration of the orbital structures (left) and visualization of the chiasm (top right) and bone (right)

Fig.2. Normal case. Different image parameters (soft tissue - left; bone - right) allow evaluation of the levels of the sellar floor (top) and aditus (bottom)

20

Fig.3. Normal case: visualization of the suprasellar cistern and of the vessels of the circle of Willis

Fig.4 Fig.5

Fig.6 Fig.7 Fig.B

Fig.4. Hyperpneumatization of the anterior clinoid processes

Fig.5. Hyperpneumatization of the anterior clinoids and partial pneumatization of the dorsum sellae

Fig.6. Both dorsum and anterior clinoids are pneumatized

Fig.7. Hyperpneumatization of the dorsum sellae

Fig.B. Partially "empty" sella because of central diverticulum of the arachnoid

21

Fig.9. "Empty" sella with en­larged cavity; note the image of the hypophyseal stalk in the sellar cavity (bottom right)

Fig.lO. Postsurgical "empty" sella after removal of cranio­pharyngioma

22

Fig.11. Empty sella in marked triventricular hydrocephalus; note the vessels of the circle of Willis and the impression made by the tip of the basilar trunk on the floor of the third ventricle

Fig.12. "Empty" sella (top); after administration of intravenous contrast medium appearance of two hyperdense lateral nodules within the sella (patient with hyper­prolactinemia and acromegaly)

Fig.13. Postactinic "empty" sella in patient with prolactin adenoma: at the level of the aditus two remnants which appear as hyperdense fleshy formations after ad­ministration of contrast medium

Fig.14. Central (bottom) intrasellar "microade­noma", hyperdense after administration of con­trast medium, corresponding to modest deformity of the dorsum sellae in patient with increased serum prolactin

23

24

Fig.1S. Small intrasellar adenoma secreting prolactin (operative check)

Fig.16. Intrasellar adenoma more developed on the left: note difference of visualization according to angulation of cut, and bone deformity corresponding to tumor nodule

25

Fig.l7. Displacement of sellar floor in patient with probable prolactin-secretingmicroadenoma not demonstrated by CT

Fig.lB. Sellar adenoma with left paramedian suprasellar development; note relation­ship to sylvian vessels and horns and occupation of suprasellar space. Study of suprasellar cistern of lamina terminalis cistern demonstrates the extracerebral site of tumor

26

Fig.19. Solid suprasellar adenoma with partly calcified shell; note relationship to the third ventricle

Fig.20. Sellar adenoma with mainly left laterosellar and partly retrosellar develop­ment as far as the brain stem, with which it is in contact. Lateral extension to the third ventricle

Fig.21. Extensive suprasellar adenoma with an anterosuperior cystic component. Note irregular thickening of optic nerves from chronic stasis

Fig,22. Sellar adenoma with partially suprasellar development before (above) and after (below) removal by nasal route

27

28

A

B

c

Fig.23. Partially calcified sellar adenoma (A); same case, after almost total removal(B);samecase, after cobalt teletherapy (C), patchy opacity of the paranasal sinuses is detectable

Fig.24. Intra- and supra-sellar cystic craniopharyngioma. Note partly calcified hypervascular shell and relationship to the ventricles

29

30

4 ~

,

Fig.25. Partly calcified sellar craniopharyngioma with small cyst immedia­tely above the sella

Fig.26. Extensive left parasellar epidermoid with irregular limits

31

Fig.27. Suprasellar epidermoid cyst with hyperdense basal nodule and hypodense zone in the superolateroposterior part of the cyst. (Below: follow-up after 6 month)

Fig.28. Asymmetrical chordoma of the clivus and of the sellar region. Note charac­teristic patchy vascularization and relationship to the encephalic structures and sinuses

32

Fig.30. Meningioma of jugum sphenoidale

Fig.29. Meningioma of left cavernous sinus, with intratumoral calcifications and thickening of the an­terior clinoid

Fig.31. Sarcoma of right orbit infiltrating region of apex of the or­bit and part of sellar region

Fig.32. Cylindroma extend­ing from apex of left or­bit to the sella; before (top) and after (bottom) radiotherapy

Fig.34. Fibrous dysplasia of right sphenoid: thickening of the bone with highly irregular density

33

Fig.33. Saccular aneurysm of left carotid siphon at the level of apex of left orbit

Fig.3S. Left parasellar arachnoid cyst with deformation of bone

Fig.36. Bullet lodged in left cavernous sinus after accidentally penetrating the left orbit and lacerating the eyeball

35

Fig.37. Mucocele of the sphenoid extending both anteriorly toward the orbital region and laterally and superiorly. Below: follow-up after surgical removal

36

Fig.38. Dysplasia of the sphenoid in Recklinghausen's disease, with deformity of the sellar cavity and hypoplasia of the sphenoidal fissure

Fig.39. Recklinghausen's disease with right retrobulbar n~oplasia and another at diencephalic suprasellar level: displacement of cistern of the lamina terminalis and of the third ventricle shows the intracerebral site of the diencephalic neo­plasia

37

Fig.40. Recklinghausen's disease: spongioblastoma unipolare of both optic nerves and right temporal neoplasia. Note invasion of chiasm and thickening and tortuosity of optic nerves

Empty Sella and Pituitary Gland 1. L. Dietemann and A. Wackenheim

It is no longer necessary to pOint out the important practical value of tomodensitometry (TDM) for diagnosing empty sellae nor the great advantage of being able to measure the density of the intrasellar contents. In practice it is now very easy to distinguish the intra­sellar densities of the parenchyma from the liquid-like densities and thus argue in favour of either a hypophysial tumoral mass or an intrasellar liquid mass, the so-called "empty sella". However, besides the problem of determining its density, there is also that of the morphology of the sellar contents, which the following case report demonstrates particularly well.

A 32-year-old female patient suspected of pituitary adenoma due to progressive obesity was referred to TDM after radiographs of the skull showed deformation of the sellar floor with a right paramedian excava­tion. TDM was performed with a C.G.R. unit (densitome). Transverse trans-sellar 6 mm sections, parallel to Virchow's plane, show intra­sellar density values ranging from 198 to 204 points-densitome. It should be emphasized that before infusion the sella had a homogeneous density and the parenchyma was not visible (Fig.1). After I.V. infusion of 250 ml contrast medium (sodium ioxithalamate), the above-mentioned hydric densities are found in the anterolateral parts of the sella turcica. Moreover, a round, opaque nodule, visible near the dorsum sellae, seems to correspond to the remaining hypophysial parenchyma (Fig.2). This is confirmed by a gas encephalography (Fig.3), which demonstrates the existence of an intrasellar arachnoidal diverticulum occupying the anterior half of the sella. Behind this diverticulum is an opacity corresponding in size and location to that seen in TDM.

Fig.1 Fig.2

Fig.1. Magnified image of the sella turcica before infusion showing homogeneous intrasellar content with densities ranging from 198 to 204 points-densitome

Fig.2. Same magnification after contrast infusion showing a hyperdense area (densities from 205 to 210 points-densitome at the level of the posterior part of the sella turcica which seems to correspond to the remaining hypophysial paren­chyma

Fig.3. Sagittal tomography in pneumoencephalography centered on the sella turcica showing the presence of an intrasellar arachnoidal diverticulum

Midline Lesions D. Baleriaux-Waha, L. L. Mortelmans, M. Dupont, and L. Jeanmart

Introduction

Lesions of the midline are often characterized by discrete symptomato­logy. Vague mental disturbances and postural headaches are often a symptom of the midline syndrome, but only a sudden intracranial hyper­tension suggests the diagnosis. Until now it has been necessary to perform invasive neuroradiologic examinations such as pneumoencephalo­graphy or ventriculography in order to make a precise diagnosis; how­ever, in this particular context these techniques are not without risks. CT scanning actually gives precise information, even about small mid­line lesions, and seems to be a valuable and non-invasive substitute to conventional neuroradiologic investigations. The CT differential diagnosis of midline lesions is discussed here, excluding sellar and posterior fossa lesions.

Technique

The images are produced by a total-body Delta-scanner. The cuts are 13 mm thick and parallel to orbitomeatal line with the usual increment of 20 mm so as to obtain overlapping cuts. All our examinations are performed both before and after intravenous injection of 140 cc of contrast medium. The importance of a correct symmetric positioning of the patient's head must be emphasized.

Results

Superficial Midline Lesions

Meningiomas are often centered near or on the midline structures. Their diagnosis usually poses no problem, since these tumors present a very characteristic pattern (Fig.1.). They are well-defined, slightly hyper­dense or isodense, and are surrounded by a hypodense edematous area which is sometimes very large. After intravenous contrast injection their density increases rapidly and homogeneously with sharply defined contours (Fig.2). Frontal cuts seem to be of the utmost importance as they clearly demonstrate the relationship of the meningioma to the falx and the superior longitudinal sinus (Fig.3). This allows an easy dif­ferential diagnosis between para sagittal and falx meningioma; a possible invasion of the sinus may also be suspected. Nevertheless, a complete and selective angiographic study must still be performed preoperatively

Vascular malformations are also often located on the midline (Fig.4). Aneurysms of the anterior or posterior communicating artery are not uncommon (Fig.5). A noncalcified aneurysm is visible only after con­trast injection and may appear partially thrombosed (Fig.6).

40

without injection, an associated recent hematoma appears as a typical hyperdense lesion (Fig.S). This intracerebral hematoma develops pro­gressively into a well-defined hypodense image. Moreover subarachnoid bleeding is also clearly demonstrated on CT images: The importance of CT may be in its prognostic value for secondary ventricular en­largement which is clearly demonstrated on follow-up scans. These re­sults emphasize the need for performing scans systematically, with and without contrast medium, as well as the necessity of follow-up scans.

Angiomas are usually slightly hyperdense, but they may occur as isodense or hypodense. The contrast medium is typical but not constant; a very dense, tortuous, well-defined lesion os observed. Associated hematoma or partial calcification may also be seen. Although arteriography re­mains of the utmost importance, microangiomas not detected by angio­graphy may be diagnosed by CT scanning (Fig.7).

Deep Midline Lesions

The normal appearance of deep midline structures should be kept in mind and systematically analyzed. The two cuts A and B (Fig.S) passing through the third ventricle show a constant and typical aspect. The superior cut A passes through the posterior and superior part of the third ventricle. This structure has the shape of a hanging teardrop. The pineal shows up clearly on this cut, just under the drop, and the vein of Galen will be injected immediately beneath. The second cut, B, which passes through the anterior part of the third ventricle also presents a teardrop aspect but this time inverted, pOinting towards the typical shape of the quadrigeminal cistern. Any displacement or deformation of these structures should be attentively looked for, because it might suggest a lesion of the deep midline structures.

Gliomas of the corpus callosum and the septum pellucidum seem to be mostly heterogeneous lesions, although they may contain irregular cal­cifications (oligodendrogliomas). The third ventricle narrows and the lateral ventricles are symmetrically deformed; bilateral amputation of the frontal horns is associated with a thickening of the septum in the typical image of a "butterfly glioma" (Fig.9). A lateral shift of the choroid plexuses may occur if the glioma is posteriorly located in the splenium of the corpus callosum (Fig.10). Cystic components of the glioma occur as well-defined low density areas. After contrast injection an inhomogeneous enhancement of the tumor is usually observed, and the real extent of the tumor is seen. Cystic components, however, do not change, and it is mainly the isodense tumoral parts of the tumor which are enhanced. Peri tumoral edema is not very important if the midline structures are not shifted.

The cistern of the vein of Galen often reduces in size and is displaced backwards. Since CT scanning provides a precise diagnosis of the loc­ation and extent of this type of lesion, encephalography no longer seems useful.

Lipomas of the corpus callosum are midline low-density lesions which may be surrounded by a thin ring of calcifications. After I.V. contrast injection, associated vascular anomalies may shown up.

When pineal calcification is thicker than 1 cm, pineal body tumors must be suspected. If CT images the posterior part of the third ventricle is obliterated and presents an anterior convex border, then the anterior portion of the third ventricle is enlarged and the quadrigeminal cis­tern is displaced backwards. The lateral ventricles are also often en-

41

larged; the midline structures are usually not shifted. The tumor it­self is isodense apart from the calcifications and is enhanced homo­geneously after contrast injection.

Calcifications and cystic appearance of a tumor anteriorly situated in the third ventricle suggest a craniopharyngioma. Areas of very low density because of cholesterol deposits may be present. The isodense tumoral mass is enhanced by control injection (Fig.11).

Deep mesencephalic tumors are usually isodense and are not enhanced by contrast injection. Tumoral herniation into the third ventricle is seen especially when this ventricle is enlarged ~y agueductal stenosis or occlusion (Fig.12). Colloid cysts are well-defined, round, hyperdense lesions, partially or completely obliterating the third ventricle. Their density is homogeneously increased after contrast injection. Arachnoid cysts, on the contrary, occur as well-defined hypodense lesions show­ing no change after contrast injection.

Third ventricle metastases do not have a pathognomonic appearance; they are usually sharply defined tumors which are enhanced after contrast medium injection (Fig.13). The presence of multiple lesions is the only argument supporting a metastatic origin.

Cerebral infarction may occur electively in the thalamic region (Fig.14). In the early stages it shows up as an ill-defined low-absorption area and evolves into a well-defined lesion with a density close to that of cerebrospinal fluid. It is important to know that after contrast in­jection, the density of a recent lesion may increase, and becoming equal to that of the surrounding brain, it may be overlooked if not studied before. Old infarcts do not change after contrast injection.

Recent deep hemorrhage, often extending from the thalamus to the basal ganglia, is seen as well-defined high-density lesions. They often rup­ture into the ventricular system and may completely obliterate the third ventricle (Fig.15).

Congenital stenosis of the aqueduct is characterized by: symmetric en­largement of the lateral ventricles and dramatic enlargement of the third ventricle without any displacement. The quadrigeminal cistern is usually slightly displaced posteriorly but not obliterated, a fact which allows a differential diagnosis from other causes of aqueductal obstruction. The fourth ventricle has a normal appearance and the posterior border of the third ventricle is convex posteriorly (Fig.16).

Recently, an ectopic pinealoma (dysgerminoma) was visualized in our department: a thin hyperdense ring encircles the lateral and third ventricles. After contrast injection this ring shows up more clearly and seems to be pathognomonic for such lesions (Fig.17).

Conclusion

CT scanning seems to be of the utmost importance for diagnosing midline lesions. Not only does CT give topographic information about the lesion itself, but it also shows clearly the repercussions of the lesions on the cerebral structures. Although histologic diagnosis may also be ad­visable in some cases. Moreover CT scanning is an incomparable method for evaluating treatment and may provide an interesting basis for stereotaxic investigation.

42

Bibliography

HAHN, F., et al. : The normal range and position of the pineal gland on computed tomography. Radiology ~, 599- 600 (1976)

MUNDINGER, F., OSTERTAG, C.: Computerized tomography in stereotactic intertitial curie therapy of cerebral midline tumors. In: Cranial Computerized Tomography. Lanksch, W., Kazner, E. (eds.). Berlin-Heidelberg-New York : Springer 1976, pp. 110-111

SAGE, M. R., et al. : Radiology in the diagnosis of colloid cysts of the third ven­tricle. Brit. Radiol. (1975) 48, 708-723

THOMALSKE, G., GRAU, H., SCHAFER,~., HACKER, H.: The significance of cranial com­puterized tomography for the diagnosis of certain expansive lesions of the mid­line. In: Cranial Computerized Tomography. Lanksch, W., Kazner, E. (eds.). Berlin-Heidelberg-New York: Springer (1976) pp. 104-113

A B

A B c

Fig.l. Tuberculum sellae meningioma: A. Before intra­venous contrast injection. B. After contrast injection

Fig.2. Frontal falx meningioma; characteristic tumoral enhan­cement after I.V. contrast injection

Fig.3. Parasagittal meningioma: A. Hyperdense lesion surrounded by extensive edema. ~ogeneous enhancement of the lesion itself after contrast injection. C. Fron­tal cut demonstrating the relationship of the meningioma to the falx

A B

A B C

Fig.4. Angioma of the peri­callosal artery; associated hematoma

Fig.5. Anterior communicat­ing artery aneurisma: A. Associated intracerebral hematoma. Note hyperdense aspect of the sylvian fis­sures. B. One month later; ventricular enlargement

Fig.6. Large partially thrombosed aneurysma: A. Without contrast injection.

43

B. With contrast injection. C. Enlargement of aneurysma. (Courtesy of Dr. Somer­hausen, Cerascan)

44

I I

A B

\)P <u(? 6 Q PC

OP ~" .n

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Fig.7. Left deep lateroventricular microangioma: A.,B. Without contrast injection. ~After contrast injection

Fig.S. Shematic view of the two cuts passing through the third ventricle (so-called "mesencephalic slices" by A. WACKENHEIM and E. BABIN)

Fig.9. "Butterfly glioma" (after injection)

A

C

Fig.llA Fig.llB

B

D

Fig.12

Fig. 10. Glioma of the sple­nium of the corpus callosum: A.,B. Without I.V. contrast injection. C.,D. With con­trast injection

Fig.ll. Craniopharyngioma: A. Aspect after I.V. contrast injection. B. Control scan three months later; development of a huge cyst

Fig.12. Deep mesencephalic tumor herniating into the third ventricle

45

46

Fig. 13 Fig.14

Fig.13. Third ventricle metastasis of mammary carcinoma after I.V. contrast in­jection

Thalamic infarction

Fig.1S Fig .16 Fig.1S. Deep hematoma with rupture Lnto the ventricular system

Fig.16. Congenital stenosis of the aqueduct

Fig.17. Ectopic pinealoma: A.,B. Before contrast injec­tion. C.,D. After contrast injection

Ventriculocisternal Pathology in Children D. Touitou

The main pathologic conditions involving the ventricles and the peri­cerebral and pericerebellar cisterns are hydrocephalus and atrophies.

Hydrocephalus

Any ventricular dilatation due to increased intraventricular pressure by accumulated cephalospinal fluid is called hydrocephalus. Ventricular enlargements secondary to subcortical atrophy are thus by definition excluded. The classic causes of hydrocephalus are hypersecretion of fluid or insufficient resorption, the latter seeming to arise from an obstruction either in the ventricular system or at the level of the arachnoidal space.

Tomodensitometry is first the method of choice for the etiologic diag­nosis of hydrocephalus. When a contrast-enhanced mass is visible at the level of the choroid plexuses, of course the diagnosis of a papilloma is easy; however, because this rarely occurs, TDM is important. Since often an obstruction prevents the free passage of the cephalospinal fluid, a mono-, bi- or triventricular dilatation suggests a tumoral mass obstructing the foramen of Monro, the third ventricle or the aqueduct of Sylvius. Similarly excessive dilatation of the fourth ventricle may signal obstruction of both the foramen of Magendie and the foramina of Luschka, thus suggesting a Dandy Walker syndrome. In this case tomo­densitometry also provides information about the size of the supra­tentorial ventricular system, usually not visible in pneumoencephalo­graphy. Tetraventricular dilatation or communicating hydrocephalus are most often due to a blockage at the level of the base of the skull caused by arachnoiditis arising from an inflammatory process, i.e., meningeal hemorrhage, purulent meningitis, cellular infiltration in disturbances in the reticuloendothelial system or in leukoses.

Second, from a neurosurgical aspect tomodensitometry provides valuable data about the evolution of the condition, as the following classic develcpment of hydrocephalus shows. The evolution comprises two stages:

1. An initial acute stage: lasting some weeks, its main characteristic is reversibility. At this stage the diagnosis must be made and the drainage apparatus placed into position. The intraventricular pres­sure then increases rapidly, the ependymal cells are dislocated, the septum undergoes microscopic lacerations, and the cephalospinal fluid migrates through the ependymal membrane, causing subependymal edema, which diffuses very rapidly into the white matter but spares the gray matter. This subependymal edema is mainly located at the level of the frontal horns and secondarily in the occipital horns.

2. The chronic phase: after several 1weeks of evolution, glial atrophy M mainly frontal and occipital m develops, involving especially the axons and the glia, but the neurons still resist. In tomo-

48

densitometry the ventricular contours are clearly outlined at this stage, the blurred aspect has totally disappeared, and the thickness of the cerebral parenchyma is markedly diminished. The lesions of this second phase are irreversible.

A third application of tomodensitometry is in the postoperative follow-up.

Follow-up After Ventricular Shunt Operation in Children

The investigation aims at controlling the permeability of the shunts. Controls must be carried out frequently since insidious obstruction of the catheters can cause silent evolution of hydrocephalus. In addtion these controls permit diagnosis of short-term or long-term postopera­tive complications, i.e., subdural hematoma or infection.

Results

The shuntoperation may terminate in the following results:

1. The ventricles are no longer visible: the shunt has brought about too rapid a drainage, resulting in ventricular collapse.

2. The ventricular dilatation persists or even increases: the shunt is operating inadequately due to either a non-patent catheter or a pa­tent but nonfunctional catheter; it is impossible to know which.

3. Ventricular lobulation: there are postinfectious adhesions. However, the mere control of the thickness of the cerebral parenchyma consti­tutes real progress.

Atrophies

With tomodensitometry it is possible to differentiate cortical atrophies from corticosubcortical atrophies, the latter being either localized or diffuse.

Cortical Atrophies (Fig.1-3)

Passive dilatation of the peri cerebral cisterns characterizes cortical atrophies, which are quite frequently visualized in children with epi­lepsy, psychomotor retardation and post-traumatic sequelae, due to meningeal hemorrhage or meningo-encephalitis. The deep and enlarged sulci are then particularly clearly visible on sections close to the vertex and on the level of the sylvian fissures. Other signs of mes­encephalodiencephalic cortical atrophy are dilatation of the opto­chiasmatic cistern of Galen and lateral extension of the subtrigonal cistern, the retropulvinar cistern well visible posteriorly to the thalamus, as well as the lateropeduncular and pontocerebellar cisterns.

Corticosubcortical Atrophies

Besides the above-mentioned, signs of ventricular dilatation, either diffuse or localized, also characterize corticosubcortical atrophy. It is not always easy to display a moderate dilatation of the sulci and ventricular dilatation raises the problem of differentiating between

49

passive and active dilatation. A close study of the brain stem system, however often facilitates the diagnosis. Indeed, if there is ventri­cular dilatation with apparently normal sulci, the visualization of an enlarged cistern of Galen and enlarged retropulvinar cisterns may be an argument supporting the diagnosis of corticosubcortical atrophy.

Subcortical Atrophy

Demyelinization of the white matter characterizes this atrophy, which consists of generally malacic cavity caused by ischemia during the perinatal period that communicates with both the ventricular and cis­ternal spaces. Its extreme degree is similar to porencephalia. Because there is a disparity between the sometimes very large size of these cavities and the preciseness of the clinical signs, tomodensitometry is a very good method for the diagnosis and follow-up of such defects.

Abnormal Cavities

Leptomeningeal or Arachnoid Cyst (Fig. 6)

These congenital cystic formations do not communicate with neighbouring cisternal spaces and in pneumoencephalography behave like tumors that fail to opacify, making their diagnosis difficult. In tomodensitometry, however, they are readily displayed without prior infusion. They are predominantly located at the level of the posterior fossa (pontocerebel­lar angle, great cistern) or the supratentorial level (sylvian fissure and optochiasmatic area).

The differential diagnosis with porencephalia is difficult, but in se­veral succesive investigations tomodensitometry can detect an increase of these defects which might benefit from neurosurgery.

Hydroma or Hygroma

In this case, a pericerebral cavity, sometimes communicating with the subarachnoidal space, occurs with a bulging of the skull at the same level. Since these cavities were usually not visualized with pneumo­encephalography, their presence was suspected only when a bulging of the skull and an apneumatic area occurred at the same time.

Although the differential diagnosis from localized atrophy or localized chronic hematona (Figs.7 and 8) js still difficult, with tomodensitometry it is possible to display directly the cavity and the bony bulge.

Hydranencephaly (Fig.9)

Hydranencephaly is characterized by the abscence of the cerebral hemis­pheres. While the posterior fossa structures are usually normal and the thalamus and the posterior fossa are either normal or hypoplastic, the supratentorial space is filled with fluid.

Fig.4

Fig.S

50

Fig.1 Fig.2 Fig.3

Fig.1. Diffuse cortical atrophy (magnification x 4). Note enlargement of the cis­tern of Galen, of the retropulvinar cisterns of the Sylvian fissures and of the interhemispheric fissures

Fig.2. Localized cortical atrophy (magnification x 4). Large and deep cortical sulci underlying cerebral parenchyma is thinner. Infant with focalized epilepsy

Fig.3. Localized temporal atrophy. Note attraction of the prepontine cistern to the left

Fig.6

Fig.4. Sequelar porencephalic cavity localized to the left occipital horn

Fig.S. Large porencephalic cavity following birth traumatism

Fig.6. Arachnoid cyst of the base. Cystic cavity occupies the right temporal fossa, passes between the sella turcica and the floor of the third ventricle and extends to the left fossa

Fig.7

Fig.8

Fig.7. Bilateral subdural frontal hematoma (magnification x 4). On the left side frontally localized hematoma causes compression and deviation of the left frontal horn. It extends between the falx and the left frontal lobe. On the right side the hematoma appears only a small crescent

51

Fig.8. Localized frontoparietal chronic hematoma (magnification x 4). Compression signs have disappeared. Outlines of the cerebral parenchyma are irregular and under­lying frontal horn is dilated. Differential diagnosis of localized atrophy or hydroma is still difficult

52

Fig.9. Hydranencephaly: there is only the parenchyma of the posterior fossa, above left, and grey nuclei, above right. The entire supratentorial level is filled with cephalospinal fluid. Note the thinning out of the vault and the disjunction of the sutures

Endocranial Calcifications J. H. Vandresse, G. Comelis, and A. Rousseau

The study of intracranial calcifications has gained interest thanks to Hounsfield's application of a mathematic integration system for radiological data. This procedure permits the calculation of the density degree of calcic and ferric opacities. Thus, it has become possible to evaluate the density of all cerebral structures including calcifications and hematic deposits. Moreover, this investigation pro­vides faster diagnosis than conventional radiology.

In this paper we would like to report our experience with computer tomography in 8000 investigations carried out in the last two years on intracranial calcifications and to demonstrate with striking exam­ples the superiority of this new technique.

Physiologic Calcifications

The most common physiologic calcifications are those of the pineal gland and choroid plexuses (Fig.1). Pineal gland calcification is a frequent radiologic finding (10% - 80% of cases depending on the pa­tient's age), but it is even more frequently encountered with computer tomography. Likewise the choroid plexuses are more often visualized with CT than was the case with plain radiography, and calcifications of the falx cerebri (Fig.2) as well as of the tentorium (Fig.3) are also displayed.

Vascular and Hematic Calcifications

Although the etiologic diagnosis of arterial calcifications is usually established, we would nevertheless like to report the picture of caro­tid siphon calcification (Fig.4). Computer tomography is sufficient to demonstrate both the extent and the evolution of chronic intracerebral hematoma (Fig.S), thus making angiography usually superfluous.

With the hematic density now known, we are able to visualize the loca­tion and the extent of calcified islets and to follow-up their evolu­tion. Chronic hematomas are easily diagnosed on account of their densi­ty, thus making angiographic study unnecessary. Figure 6 shows calci­fication in chronic frontal hydroma, whereas calcified angiomas are seen to have no specific features (Fig.7).

Fahr disease

The radiologic signs of Fahr disease are characteristic enough that differential diagnosis is not needed. Two particularly illustrative cases (two brothers) with calcifications in the basal ganglia (Fig.8), dentate nuclei of the cerebellum and cerebellar cortex (Fig. 9), and calcifications in the basal ganglia of the mesencephalon and diecephalon (Fig.l0) are presented. The latter were not visible on plain films.

54

Phacomatosis

This is certainly one of the most interesting study subjects. (The cal­cifications found in cases with tuberous sclerosis have not been de­scribed yet). The picture clearly indicates the periventricular calci­fied phacoma, under the ependyma or even in the basal ganglia, and the carotid calcification. When the calcifications are intraparenchyma­tous the differential diagnosis for evolutive tumor must be considered. For this disease, too, plain radiographs of the skull and adjunctory neuroradiologic investigations do not provide more data.

Angioma trigemino-encephaliticum or Sturge-Weber syndrome is usually easily diagnosed. Figure 12 represents a case in which the plain skull film and the carotid angiography did not show any abnormality, whereas CT exhibited characteristic features, i.e., diffuse calcifications and the angioma covering the whole hemisphere which is atrophied. Although the literature reports only 13 cases with total calcification of a he­misphere diagnosed on plain skull films, the new method will probably disclose more cases. The CT diagnosis of bilateral densification has also been made in cases where plain films demonstrated only unilateral calcification.

These cases are particularly illustrative of the value of the new tech­nique.

Infections

Although the whole list of parasitoses and chronic infections which may cause calcifications will not be reviewed, the characteristic aspect of these calcifications in congenital toxoplasmosis should be noted. They are often linear, not very abundant in the early stages of the disease, and associated with a marked dilatation of the cella media of the la­teral ventricle (Fig.13), while the frontal horn shows an almost normal size (Fig.14).

The calcified areas are seen in the basal ganglia but may also be found everywhere in the cerebral parenchyma. Calcified cytomegalic inclusions may exhibit the same features but then the ventricular system is dif­fusedly dilated.

Figure 15 illustrates a case of calcified tuberculoma.

Tumoral calcifications

The main advantage of computer tomography lies in the early diagnosis of tumoral calcifications especially in cases where plain roentgen methods failed to demonstrate them. Moreover, in cases where the calCi­fications have been assessed with plain films, CT permits precise de­monstration of the extent of the tumor. Often distribution and location of the calcifications give a clue as to the probable diagnosis.

Tumoral calcifications are commonly seen in ependymomas, craniopharyn­giomas, meningiomas and oligodendrogliomas, as well as also in about 13 per cent of other tumoral types. The presence of a very central, median or paramedian calcification, occupying the area of the third ventricle is very evocative of craniopharyngioma (Fig.16), the more so if it is of the annular type (Fig.17). Calcified pituitary adenomas are also to be seen.

55

With CT small meningiomas which were not visible with plain films or with cerebral angiography were also recognized. Occipital calcifications in the supra and infratentorial space are very likely consistent with tentorial meningioma. Atypical calcifications in a heterogenous paren­chyma suggest a glial tumor. Finally, a chordoma of the apex of the petrous bone was also displayed, extending to the whole sellar area up to the vertex (Fig.18).

Leukemias

In three cases CT visualized intracranial calcifications in children with acute lymphatic leukemia in whom the plain skull radiographs were normal. This complication involves the basal ganglia (Fig.19) as well as the cerebral cortex (Fig.20).

The precise etiology of these calcifications is still unknown. It might be a lesion caused by the disease itself or by the chemotherapy or, more likely, by radiotherapy. It could also be a matter of microbleed­ing, secondarily calcified. The differential diagnosis for Sturge-Weber syndrome with meningoencephalitis and with calcified gliomas must be considered. CT investigations will probably facilitate discovery of more similar cases, since the therapeutics applied in acute lymphoid leukemia bring about longer remission periods.

Conclusion

As concerns endocranial calcifications, systematic CT investigations certainly provide as much data as the conventional methods. Moreover, they provide a better knowledge of the location and extension of the calcifications within the normal or pathologic parenchyma.

Bibliography

AMBROSE, J.: computerized transverse axial scanning (tomography). Part 2. Clinical application. Brit. J. Radiol. 46, 1023-1047 (1973)

AMBROSE, J.: Computerized X-ray scanning of~e brain. J. Neurol. 40, 679-695 (1974)

BORNS, P.F., RANCIER, L.F.: Cerebral calcification in childhood leukemie mimicking Sturge-Weber syndrome. Amer. J. Roentgenol .. Ther. Nucl. Med. ~ 52-55 (1974)

COLLARD, M., DUPONT, H.P.: La tomographie axiale transverse computerisee par EMI­Scanner, premier bilan apres 1000 observations. J. Belge Radiol. 58, 289-328 (1975)

DAVIS, D.O., PRESSMANN, B.D.: Computerized tomography of the brain. Radiol. Clin. N. Amer. XII, 297-313 (1974)

GOMEZ, M.R., MELLINGER, J.F., REESE, D.: The use of computerized transaxial tomo­graphy in the diagnosis of tuberous sclerosis. Mayo Clin. Proc. 50, 553-556 (1975)

METZGER, K., BEN HAMIBA, M.: Les calcifications intracraniennes. Concours med., suppl. au 21 du 23 mai 1970. (Documentation medicale permanente du medicin praticien) .

NEW, P.F., SCOTT, W.R., TAVERAS, J.M.: Computerized axial tomography with the Emi­Scanner. Radiology 110, 109-123 (1974)

OZONOFF, M.B., BURROWS,~M.: Intracranial calcificative, chap. 41. Radiology of the Skull and Brain. The Skull. Th. Newton and D.G. Potts.

PAXTON, R., AMBROSE, J.: The Emi-Scanner. A brief review of the first 650 patients. Brit. J. Radiol. il, 530-565 (1974)

SPEHL, M., FLAMENT, J., MAURUS, R., DELALIEUX, G., BRIHAYE, J., CREMER, N.: Calcifications intraniennes diffuses apparaissant a la suite d'une leucemie aigue. Ann. Radiol. 12, 417-422 (1974)

VANDRESSE et al.: Etude des calcifications endocraniennes par encephalotomographie computee. J. Belge Radiol. 59, 239-251 (1976)

WACKENHEIM, A.: Radio-Anatomie Normale et Pathologie du Crane. Paris: G. Doin Cie. 1960.

SYMPOSIUM NEURORADIOLOGICUM. Bruxelles, 23-24 septembre 1972.

Fig.1 Fig.2 Fig.3

Fig.4 Fig.5 Fig.6

Fig.7 Fig.8 Fig.9

57

Fig.l0 Fig.11 Fig.12

Fig.13 Fig.14 Fig.1S

Fig.16 Fig .17 Fig.1S

58

Fig.19 Fig. 20

Area of Maximal Density in Extracerebral Tumors J. c. Dosch

The tomodensitometric image of a structure is a colorimetric pattern for which similar densities produce identical shades, the distribution in one plane of which determines the shape of the image. Therefore it is useful to study the distribution of densities in the various cere­bral lesions, especially in extracerebral tumors.

Method

The C.G.R. densitome allows isodensity to be depicted with a higher degree of brillance than the original tomodensitometric image on the cathode ray tube, where the particle of normal or pathologic cerebral parenchyma has the same absorption coefficient. The absorption coeffi­cient is linearly related to the density levels, the distribution of which ranges from 0 to 511 points on the densitome scale 200 correspond­ing to water and to C.S.F. density. By varying the level of high densi­ties, the overbrilliant points are changed, and a map of the densities within the various cerebral tumors can be drawn. Following injection of a contrast medium, this same examination permits the analysis of the tumor's densitometric dynamics. The isodensity option of selecting the density level as well as the number of densities (between 1 and 16 points) is independent of the window and of the density level of the den­sitometric image visualized on the console display. For intracerebral pathology we proceed to a pOint-by-point study differing from the me­thod used in ophtalmologic pathology.

Material

From 1000 tomodensitometric examinations we selected

12 extracerebral tumors (6 meningiomas and 6 acoustic neurinomas); 2 intraventricular tumors (1 papilloma and 1 meningioma)

The study of these lesions was followed by calculation of the data pro­vided by magnification, in profiles and histograms, the latter two re­presenting directly the distribution of isodense points around a line (profile) or within a volume (histogram).

Results

1. The area of maximal density for the extracerebral tumors is located close to the bony structures, i.e., the vault for the meningiomas, the porus of the internal auditory meatus for the neurinomas. (Figs.1-11). 2. The area of higher density for intraventricular meningiomas corres­ponds to the arterial pedicle, a finding confirmed by surgery. 3. The area of maximal density for the papillomas is located at the theoretical location of the choroid plexus. (Figs.12-16).

Thus in our present material the maximal density of an extracerebral tumor corresponds to the area of osteomeningeal insertion, or at least to its nutritional pole.

Discussion

Since spontaneous hyperdensity was absent, the maximal density after intravenous infusion of contrast medium was considered. The subsequent analysis of the tomodensitometrical distribution must be carried out on a purely tumoral slice, for which the studied part must be located between at least three layers of adjacent sections.

For voluminous tumors involving several section layers the area of maximal density is always located close to the insertion pole (e.g., the meningiomas of the convexity or of the falx), but may vary some­what. Under these circumstances the tomodensitometrical section with the maximal density passes through the nutritional pole.

The presence within the tumor of calcic deposits of course disturbs such a distribution (e.g., psammonas .•. ) and must not be confused with the density of the insertion.

Summary

In different kinds of extracerebral tumors, the highest density level is located close to the insertion of the tumor (meningiomasineurinomas~ papillomas) .

Fig.2

Fig.l. Meningioma of the right parietal convexity. The display hyperdensity is obtained after intravenous infu­sion of contrast medium

Fig.3 Fig.4

Fig.2. Magnification (x 2) of the same meningioma

Fig.3-4. Visualization of the area with maximal density. The more or less darkening of the magnified tomodensitometric picture as seen in Figure 2 helps to determine the extracerebral location of the tumor. It is clearly located close to the vault (Fig.4)

'" ... > ... -'

Profile Around Line 58

223r-;--+~r-+--r-1--+-~-+--r-1--+--~

120 11.0 Number of Columns

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61

Fig.5. Profile around the line through the maximal density area. There is no solu­tion of continuity on the right, between the vault and the meningioma, which has a decreasing density from the vault dawnwards. The median peak corresponds to the hyperdensity of the falx and of the anterior cerebral arteries and veins

Fig.6 Fig.7 Fig.B

Fig.6. Left acoustic neurinoma after contrast infusion

Fig.7. Magnification (x 2) of the same neurinoma. The magnification is obtained by means of an appropriate informatic treatment (PRINTING-DEVICE)

Fig.B. Visualization of the area of maximal density. Special equipment allows visualization of the maximal density by darkening the original CT picture displayed in Figure 1

62

Fig.9. Magnification and visualization of the area of maximal density and of the bony countours of the skull base. Insertion area is located in front of the left internal auditory porus

Fig.l0. 1/1 scale image of Figure 1

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63

Fig.ll. Profile around line passing through area of maximal density. The absence of a gap between the hyperdense area accounts for the extracerebral nature of the tumor

Fig.12. Papilloma of the fourth ventricle. Prior to infusion of contrast medium absence of visu­alization of the fourth ventri­cle (A) associated with obstruc­tive hydrocephalus (e) is noted on the midline. After infusion a hyperdensity appears (B), ex­tending to the dilated aqueduct of Sylvius (D)

64

Fig.14 Fig.1S

Profile Around line 77

Fig.!3. Magnification of the same papilloma

Fig.14-1S. Visualization of the maximal density area. The 3 points correspond to the theoretical location of the choroid plexuses and of the posterior inferior cerebellar artery, PICA

218.----....---.---.-,--i---.---.-,-....---.---.-,--.-.

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Fig.16. Profile around the 77th line passing through the choroid plexuses. The first and second peak cor­respond to the hyperdense area and delineate the in­traventricular tumor at this level

Tumoral Masses of the Posterior Fossa B. Staelens, Y. Palmers, A. L. Baert, and J.-L. Termote

In its early applications, CT was the preferred method for obtaining additional information in complex cases already studied by angio­graphy and gas encephalography. Nowadays CT has grown into a screening examination for all patients suspected of an organic cerebral patho­logy, including a pathology of the posterior fossa.

The processes occupying the infratentorial space constitute a parti­cularly difficult domain, both from a diagnostic as well as a thera­peutic point of view. And the grave complications and serious surgical problems that can be caused by posterior fossa masses are well known. The incidence of these tumors varies according to the age of the pa­tient; in adults, 20-25% of all brain tumors are posterior fossa mas­ses, whereas in children this percentage may be as high as 50-60%.

It is useful to recall some morphologic details about the exact boun­daries of the posterior fossa in order to determine whether or not a given lesion lies in the posterior fossa. The cerebellum, located in the posterior fossa of the skull behind the porus and medulla, is separated from the overlying cerebrum by an extension of dura mater, the tentorium cerebelli, is oval in shape and its widest diameter runs along the transverse axis. The cerebellum is similar to a tent, with its upper ridge line carried by the straight sinus on its trajectory from the quadrigeminal cistern to the internal occipital protuberance, while its lower and horizontal margins are inserted on both sides at the level of the transverse sinus, from the torcular Herophili to the superior border of the petrous bone. The insertion of the tentorium follows the upper edge of the petrous bone forwards and inwards up to the posterior clinoid processes. The free margin of the tentorium, enclosing the cerebral peduncle and the upper part of the brain stem, constitutes the entrance of the posterior fossa. After injection of contrast medium the position of the tentorium cerebelli is generally determinable on enhancement of the veins, with its subsequent CT images.

The examination is performed with the patient's head in the orbito­meatal position and the X-ray beam parallel to the orbitomeatal plane. Another position, orbitomeatal +150 , is proposed by many authors, and in some cases (particularly in children or if the first series of images present too many artifacts) this semiaxial sectioning plane has proved to be of considerable value. Still anotper method for pos­terior fossa exploration by CT is the performance of thin sections (i.e., 8 mm) or partially overlapping sections, because only then is an accurate CT exploration of the cisterns of the posterior fossa and of the region of the incisura tentorii possible.

In all patients suspected of a posterior fossa problem the examination is begun with a low cut through the bony structures of the base of the skull. Sometimes interpretation of the CT images of the posterior fossa is impeded due to artifacts (from calculation faults) interfering with the image formation. An example is the striking starshaped high-density artifacts often seen in adult patients with a rather prominent inner occipital protuberance.

66

The area between the two tops of the petrous pyramids sometimes shows another low-density artifact, particularly if there is a marked area­tion of the mastoid region. The disturbing artifacts caused by drop­lets of lipiodol in the fourth ventricle and in the basal cisterns need not be explicated here.

Indications

A CT examination should not be performed without precise clinical in­formation. Nevertheless, on all the patients who corne for a CT examin­ation two sections through the posterior fossa, even when there are no obvious cerebellar clinical signs, are done routinely. The space­occupying lesions of the posterior fossa can be responsible for the following syndromes:

1. The cornmon syndrome of intracranial hypertension, a hydraulic defect of the circulation of cerebrospinal fluid, reveals two groups of clini­cal signs: the symptoms of intracranial hypertension (morning headache, vomiting, blurred vision caused by papillary stasis and slackening of the psychic functions) and the cerebello-vestibulary syndrome (vertigo, horizontal nystagmus, abnormal attitudes).

2. The vermian cerebellar syndrome with signs of static incoordination.

3. The hemispheric cerebellar syndrome with disturbances of motor co­ordination and muscle tone.

4. Involvement of the brain stern, affecting the long sensory, motor and cerebellar tracts.

5. Isolated condition of a single cranial nerve, particularly in its subarachnoid trajectory. A frequent finding in the VIIIth cranial nerve, this condition is an early sign of an acoustic neurinoma.

Histologic Classification of Posterior Fossa Tumors

1. Neuro-epithelial tumors: astrocytoma, spongioblastoma, ependymoma and medulloblastoma.

2. Mesodermic tumors: meningioma, sarcoma, hemangioma and angioblastoma (von Hippel - Lindau).

3. Tumors of the cranial nerves: neurinoma. 4. Tumors of dysgenetic origin: teratoma, dermoid and

epidermoid cysts. 5. Metastasis.

Posterior fossa masses can be divided in two groups according to their topography.

1. Tumors of the Brain Stern (or Intra-axial Tumors)

The CT pictures of these very rare tumors seen mostly in children and adolescents, are quite polymorphic and variable.

Since the majority of patients with a brain stern tumor are admitted directly to the radiotherapeutic ward, the exact histologic diagnosis remains unknown.

CT provides valuable topographical data on intra-axial tumors, giving information about the extension of the neoplasm in the surrounding

67

tissue, if any. But CT cannot give any information concerning the nature of an intra-axial tumor, although it can for extra-axial mas­ses. Most of these tumors being gliomas their prognosis is poor. An astrocytoma of the brain stem usually appears as a low-density lesion on the precontrast as well as on the postcontrast CT scan.

2. Extra-axial tumors

a) Extraparenchymatous tumors: These lesions cause a compression and . a displacement of the brain stem. Most are neurinomas of the VIIIth or the Vth cranial nerve, with meningioma of the clivus or of the frontocerebellar angle, chordomas and dermoid cysts seldom occurring.

The CT image of an acoustic neurinoma generally shows a poorly defined mass of slightly decreased or sometimes increased density; which may also be isodense and invisible prior to contrast in­jection. After injection, however, the tumor is more clearly out­lined and is seen on at least one section to touch the posterior aspect of the petrous pyramid. Its density after contrast en­hancement varies between 50-80 Hounsfield units and can even reach 120 Hounsfield units.

A few of these tumors, particularly the smaller ones, are less defined (even after contrast enhancement) probably due to par­tial-volume effect on the performed sections. Sometimes a tiny low-density, ringlike area is present around these tumors; in exceptional cases this is very extensive. The accompanying edema or atrophy of the adjacent cerebral tissue (the degree of pre­sent edema correlates with the growth rate) is most likely the cause.

A certain number of acoustic tumors can have a partially cystic appearance.

Hydrocephalus is seen in 30-50% of the cases. The fourth ventricle is practically always shifted to the opposite side of the lesion.

A neurinoma of the Vth cranial nerve is located more ant.eriorly on the petrous pyramid, frequently passing through the incisura ten­torii. The CT image reflects this in an ipsilateral distortion of the quadrigeminal cistern, an amputation of the posterior as­pect of the third ventricle, or forward displacement of the ip­silateral temporal ventricular horn.

A meningioma is visible on the plain CT image as a well-defined mass of slightly increased density, mostly in close contact with a wall of the posterior fossa and sometimes studded with calcium deposits. After contrast enhancement all meningiomas present a sharply outlined density of 70-120 Hounsfield units which are surrounded by a thin, low-density ringlike area also seen in some neurinomas. Hydrocephalus is commonly present (according to Thomas NAIDICH).

The differential diagnosis between intra- and extra-axial masses is often difficult, particularly for tumors with median or para­median extensions. A few signs, however, help differentiate since they favour an extra-axial origin.

68

1. Erosion or destruction of the adjacent bone structures. 2. Apparent continuity of the tumoral mass and the tentorium cerebelli or the bony walls of the posterior fossa. 3. A well-defined lesion after contrast enhancement. This valu­able sign, however, is not absolutely exclusive because well­defined high-density zones in the brain stem area are found in well-vascularized metastases of a hypernephroma, in a hematoma and in a tuberculoma (in the latter two a precontrast CT scan is very useful for further differentiation.).

b) Cerebellar Tumors: Although these tumors are very frequent in childhood, there is in general less peritumoral edema in children than in adults. Astrocytomas, spongioblastomas and ependymomas are relatively benign. Since uptake of contrast medium varies widely according to the degree of histologic differentiation of the tumor, the CT image of cerebellar tumors is far from specific. Nevertheless, some observations can be helpful.

Subtentorial gliomas are less frequently contrast enhancing than their supratentorial congeners.

Medulloblastomas, very malignant tumors, yield a markedly de­creased absorption value on the precontrast CT image, but in a number of cases they show considerable contrast enhancement after injection of contrast medium. Differentiation from ependymomas can be difficult.

The multiple hemangioblastomas of the von Hippel - Lindau disease show multiple high-density areas, a highly specific postcontrast image. But it should be mentioned that in some cases a strong uptake of contrast medium is first observed up to 45 min after the onset of a rapid intravenous infusion of the contrast product.

Generally CT can detect and locate a tumoral mass of the posterior fossa. In some cases, even the nature of the tumor can be roughly estimated (cystic or solid, with or without necrotic areas, cal­cifications, clotted blood), and the tumoral mass itself can be differentiated from the accompanying reactive edema.

One of the main problems of differential diagnosis is posed by ischemic lesions in patients who have suffered from vertebro­basilary insufficiency for years. A good knowledge of their cli­nical history on the one hand and follow-up CT images on the other help orient the diagnosis. However, an ischemic lesion provokes a hydrocephalus less commonly than a tumor, and its mass is usually very modest.

A brain stem hematoma examined by CT only after injection of con­trast material may be mistaken for an acoustic neurinoma, thus illustrating why a CT scan for all potential lesions of the pos­terior fossa must be performed both before and after injection of contrast medium.

A subdural or extradural hematoma, acute or chronic, cannot be mistaken for a tumor, providing the images are of good quality, not always the case when the patient is restless or semicomatose.

Finally there is the problem of patients whose CT image shows hydrocephalus and a posterior fossa within the normal limits or a poorly visualized fourth ventricle, e.g., in aqueduct stenosis.

In these case ventriculography with positive contrast medium or gasencephalography (or gascisternography) are recommended, rather than wait a few days or weeks before performing a CT control scan.

Conclusions

CT has become the method of choice for defining the topography of tumoral masses of the posterior fossa, but not for determining the specific nature of a tumor, which in a number of cases is more dif­ficult with CT. The few criteria described earlier and the clinical history of the patient generally suggest a rather specific diagnosis. Nevertheless, the classic methods of neuroradiologic investigation have not yet lost their importance, rather their indication has be­come better assessed. And, the use of CT requires certain indispensable exigencies, e.g., above all, as J.L. Thomson has said, the attention of an observer not only widely experienced in the diverse variety of in­tracranial lesions but also capable of undertaking a range of neuro­radiologic investigations if called for. Only under such circumstances is CT an immensely valuable technique. Also centers that are not fully equipped should carefully weigh all alternatives prior to the instal­lation of a CT scanner.

In the future, more highly perfected CT scanners will improve the CT images of the posterior fossa and the basal cisterns, thus permitting a more accurate diagnosis and perhaps even taking the place of some of the more drastic and dangerous classic procedures of neuroradiology.

We acknowledge the precious aid of Dr. G.A.J. TOPS for the translation into English.

Bibliography

HARWOOD-NASH, D.C.: Congenital Craniocerebral abnormalities and computed tomography. Semin. Roentgenol. JjL, (1977)

KAZNER, E., LANKSCH, W., STEINHOFF, H.: Cranial computerized tomography in the diagnosis of brain disorders in infants and children. Neuropadiatrie,~,

136-174 (1976) NAIDICH, T.P. et al.: Computed tomography in the diagnosis of extraaxial posterior

fossa masses. Radiology 120, 333-339 (1976) PENN, R.D. et al.: Tumor volume, luxury perfusion, and regional blood volume changes

in man visualized by subtraction computerized tomography. J. Neurosurg. ~,

449~457 (1976) SALOMON, G. et al.: La tomographie axiale avec ordinateur - Correlations neuro­

radiologiques. Traite de Radiodiagnostic 14, 599-623 (1976) SALOMON, G. et al.: Tumeurs de la fosse cerebrale posterieure. Introduction

clinique. Traite de radiodiagnostic li, 389-395 (1976) THOMPSON, J.L.G.: Computerised axial tomography and the diagnosis of glioma:

A study of 100 consecutive histologically proven cases. Clin. Radiol. 1QJ 431-441 (1976)

WACKENHEIM, A., BRAUN, J.P.: Tumeurs du mesencephale. Traite de radiodiagnostic li, 355-366 (1976)

70

A B

Fig.t. (Patient N.) Cystic tumor at the level of the medulla oblongata (gliomatous tumor). A. CT section through C 0; two low-density areas are visible which corres­pond to cystic structures. The x-ray absorption values are compatible with the presence of a liquid with slightly higher density than cerebrospinal fluid. B. The air-study demonstrates an enlargement of the medulla oblongata at the C 0 level

A

B

Fig.2. (Patient L.V.) A. The CT scan of this child with papillary stasis and hydro­cephaly shows a poorly defined low-density area at the right cerebellopontine angle which does not change after injection of contrast medium. The fourth ventricle is not clearly visualized. B. Triventricular hydrocephaly. The quadrigeminal cistern· (or cistern of the great vein of Galen) is deformed and compressed. Ventriculography illustrates the displacement and particularly the irregular distortion of the fourth ventricle. During the surgical intervention in the right cerebellar hemis­phere and the brain stem tumor was found in the fourth ventricle

A

c

71

B

D

Fig.3. (Patient P.) A. A high-density zone is present at the right side of the quadrigeminal plate area, with distortion and partial obliteration of the quadri­geminal cistern. Triventricular hydrocephalus and a slight impression on the right postero-inferior aspect of the third ventricle. B. The same CT image after injec­tion or contrast medium. C. and D. Gasencephalography (A.P. and lateral aspect) . A tumoral mass protudes into the right cisterna ambiens. The aqueduct of Sylvius is shifted on the A. P. planigram

A

C

E

G

72

B

o

F

H

Fig.4. (Patient W.I.) A. A retinoblastoma of the left eye of this child has been removed surgically. B. The child was admitted to the hospital in a comatous state. On CT there is a triventricular hydrocephalus, an area of increased density in the upper part of the brain stem and a marked asymmetry of the quadrigeminal cistern. The hyperdense area corresponds to a brain stem hematoma. C. Minimal contrast en­hancement in this area. D. At a higher section the calcified pineal body displaces the posterior aspect of the third ventricle. E. After a few weeks of radiotherapy, the clinical condition of the child improved and the hematoma subsided. The quadri­geminal cistern restored its normal size and shape. F. The hydrocephalus has dis­appeared; only the third ventricle remains rather enlarged. G. After a few months, hydrocephalus reappeared. The quadrigeminal cistern is almost completely obliterated. H. After infusion of contrast medium, a dense opacity appears in the area of the pineal gland, corresponding to pineal location of the retinoblastoma

A

C

73

A B

Fig.5. (Patient B.A.) Relapse of a medulloblastoma. A. This CT image before contrast enhancement shows an area of slightly increased density situated high in the brain stem, with displacement of the third ventricle and deformation of the temporal ven­tricular horn. Lipiodol droplets administered. B. After contrast enhancement there is marked homogeneous contrast uptake in the tumor. Peri tumoral edema is minor

B

Fig.6 . (Patient G.M.) Neurinoma of the facial nerve. A. The pre contrast CT image shows only a slight asymmetry of the frontocerebellar cisterns. B. After injection of contrast medium, a small tumoral opacity appears in close contact with the pos­terior surface of the petrous pyramid. C. The air-study clearly demonstrates the small tumor within the cerebellopontine cistern, facing the internal auditory meatus

74

A B

Fig.7. (Patient M.) Acoustic neurinoma. A. Pre contrast CT scan: the shift of the fourth ventricle is the only reliable sign. B. Postcontrast CT scan: a homogeneous, rather dense, and well-defined mass is visible now

A B

C 0

Fig.B. (Patients D.P. and T.) Acoustic neurinoma. A. Before contrast injection. Note the small rounded, low-density area above the right petrous bone. B. The same patient after contrast injection. Partial obliteration of the quadrigeminal cistern. A more or less well-defined enhanced area within it corresponds to an intratumoral cyst. C. CT before contrast enhancement. Shift of the fourth ventricle to the left. Destruction of the apex of the right petrous pyramid. Notice the slightly hypodense area in the right cerebellopontine angle. Remaining droplets of lipiodol administered. D. The same patient after contrast enhancement. A large, well-defined tumoral mass, homogeneously filled with contrast medium, is visible now

75

Fig.9. (Patient I.F.) Meningioma. The precontrast CT image shows a rounded area of decreased density at the posterior aspect of the petrous pyramid. This area is surrounded by a tiny hypcdense halo. The fourth ventricle is not visualized

A B

Fig.lO. (Patient D.A.) Tentorial meningioma. A. In this woman, already surgically treated for a meningioma of the small sphenoid wing, the plain CT scan shows a right occipital area of slightly increased density, a triventricular hydrocephalus and a shift to the left of the third ventricle. B. After injection of contrast medium, the area mentioned above enhanced intensely and homogeneously. There is also a recurrence of the previously removed sphenoid wing meningioma

76

A B

C D

Fig.!!. (Patient D.W.) Hemangioblastoma. A. and B. The image (before and after contrast injection) shows a low-density area on the right side in the posterior fossa. There is no contrast enhancement at this level. The lesion crosses the midline. For several months repeated CT examinations established an identical image. The fourth ventricle is flattened and shiftened forward and to the left side. C. and D. With iodine ventriculography the aqueduct and the fourth ventricle are proven displaced, and a distortion due to tumoral ingrowth is noticed

A B

Fig.!2. (Patient B.A.) Relapse of a cerebellar ependymoma. A. The precontrast CT image demonstrates a poorly defined low-density area in the middle of the posterior fossa, the cause of which is difficult to ascertain - either due to postsurgical sequels or to peritumoral edema. A few remaining droplets of lipiodol are administer­ed. B. After injection of contrast medium there is a localized contrast uptake which makes the low-density area appear smaller. The basal cisterns are hardly visible

A B

Fig.13. (Patient H.) Recurrence of a hemangioblastoma. operative sequels: trepanation hole. The cisterna magna contrast image: a well-enhanced, homogeneous, clear-cut

A B

77

A. Precontrast image. Post­is not visible. B. Post­opacity is visualized

Fig.14. A. Patient C. V.: after contrast injection. Metastasic the superior vermis (the primary tumor was a lung carcinoma) . Metastasic hiqh-density lesion with perifocal edema

low-density lesion in B. Patient E.J.:

78

A B

Fig.iS. Hematomas. A. Patient T.S.: Intraventricular blood collection in the fourth ventricle. The increased absorption value is typical of clotted blood. B. Patient K.L.: Chronic posterior fossa subdural hematoma in a mentally retarded child. The peripheral right sickle-shaped low-density area near the occipital bone corresponds to a collection of degenerated blood after osmotic dilution. Notice the mass effect, provoking displacement of the fourth ventricle

Fig.16. (Patient D.N.) Dandy Walker syndrome. Large cystic area communicating with the fourth ventricle (its density is similar to that of C.S.F.). High position of the tentorium cerebelli. Considerable spreading of the ventricular cross points and of the posterior horns

Cerebellopontine Expansive Lesions u. Salvolini, F. Menichelli, and U. Pasquini

The aim of this study is to assess the results of CT in the diagnosis of expansive lesions of the cerebellopontine angle, its clinical re­percussions, and its value in comparison with other conventional neu­roradiologic investigations. Of the many contributions in the litera­ture on the value of CT in the diagnosis of intracranial diseases we cite only the most recent which have concentrated on the problem of expansive lesions of the cerebellopontine angle (FAWCITT and ISHER­WOOD 1976; GYLDENSTED et al. 1976; NAIDICH et al. 1976; KENDALL and SYMON 1977).

Material and Method

Our experience is based on 77 cases of expansive lesions of the cere­bellopontine angle (CTA) drawn from a series of 5000 patients inves­tigated at the Radiology Service of the Ancona Regional General Hos­pital in the course of 18 months. All patients were examined on the operating or dissecting table with an EMI-Scanner Mark 1 160 x 160 matrix and results were analyzed on the Diagnostic Display Console (DOC) •

The following technical details characterized the CT examination:

1. The patients were immobilized by a chin-stop of our own design; uncooperative patients were sedated or, rarely, anesthetized.

2. The standard angle of incidence for studying the posterior cranial fossa has a 200 angulation between the scanning plane and the or­bitomeatal line; in some cases, for the study of the orbit and tentorial notch, an angulation parallel to the Frankfurt plane was used.

3. The slices were 13 mm thick for the whole head and 8 mm for investi­gating regions in detail.

4. Contiguous slices were scanned and, where necessary, also slices with partial overlap.

5. The results were read on the DOC, care being taken to assess the bone at petrous bone level by varying the level and amplitude of the viewing window (SALVOLINI et al. 1976).

6. In all cases an investigation also followed infusion of an iodized contrast medium (Angiografin Schering 65%) at the dosage of 2 cc/kg body wt

Obviously CT investigation was preceded by clinical examination, plain X-rays, and by multidirectional tomography of the petrous bones and was followed by all the neuroradiologic investigations necessary for a full understanding of the case.

The 77 cases fell into the following categories:

45 neurinomas, 15 meningiomas, 7 epidermoids, 10 other lesions (metas­tases, aneurysm, abscess, glomus jugular tumor, etc.).

Of the 45 neurinomas, 32 were examined preoperatively and only 13 postoperatively; of the latter, 8 with sizable remains. Of the 15 meningiomas, 13 were examined preoperatively and 2 postoperatively with definite remains. Of the epidermoids, 4 were examined preopera­tively and 3 postoperatively, the latter with remains. The result of the study of the patients operated on is rather interesting: of the 26 cases checked postoperatively only 9 were without remains or re­currences, as many as 17 presenting neoplastic tissue. Some 50% of the neurinoma and epidermoid cases examined after operation were found to have large remains or actual regrowth. These patients did not corne from a single neurosurgical center but from several centers; it should also be noted that no systematic investigation of all patients was made; in most of the patients who reached us the disturbances for which they were operated had either remained or reappeared postopera­tively.

Another point to note is that the variations in the size of the ven­tricles in hydrocephalus cases after operation were checked: in nearly all the operated cases the subependyrnal periventricular hypodensity found before operation due to transependyrnal transit of C.S.F. dis­appeared.

Brief Notes on the CT Characters of the Various Lesions

Neurinomas

Generally hypodense or isodense with reference to brain tissue before administration of contrast medium, they become hyperdense after: it is therefore possible at this stage to establish whether they are solid or cystic. Systematic study of the petrous bones often reveals the dilatation of the internal auditory meatus or any erosion of the petrous bone. The majority of the neurinomas examined were over 1 cm in dia­meter and most of the largest ones developed upward laterally toward the mesencephalon.

More than any other method, CT permits the clear assessment of these relationships

Meningiomas

Generally hyperdense to start with, they may present irregular calci­fied nuclei. After injection of the contrast medium the density in­creases considerably and in 50% of cases a peripheral vascular pedicle is detected. In cases of intrusion of the petrous bone, the latter's structure becomes thicker, but the internal auditory canals are not widened.

Epidermoids

Hypodense to start with, they are multilobate and sometimes septate; after I.V. injection of the contrast medium at very high dosages it is sometimes possible to detect a thin hyperdense rim around the growth. Study of the connections with the tentorium with a view to assessing any supratentorial development is of particular interest.

81

Other lesions

CT has the important advantage in the case of aneurysms of being able to demonstrate the real extent of an almost completely thrombosed an­eurysmal sac. In the case of abscesses CT permits a systematic serial examination of their development through time. And in glomus jugular tumor growing vertically CT reveals the concomitant intracranial situation as well.

Limits

There are, however, limits to CT, partly technical ones and partly human ones. The following are briefly recalled:

1. Lesion size: lesions with a diameter less than 0.5 cm were not de­monstrated. Although intracisternal lesions of even smaller volume have been detected by intrathecal injection of contrast medium, (Metrizamide), but unfortunately our country does not permit use of this substance and so we have no personal experience of it. Excel­lent results obtained from this method are documented in GREPE et al. 1975.

2. Site: we have never demonstrated exclusively intracanalicular neu­rinomas. In fact, in one such case we had a false negative, although probably with higher definition data could be obtained in this field too.

3. Patient Cooperation: this is vital because, especially in a region rich in high-density structures like the posterior cranial fossa, even the slightest movement produces artifacts which make the pic­ture illegible. In rare cases sedation is necessary and, exception­ally, anesthesia.

4. Interpretation: there is no substitute for personal experience in assessing results and even in correctly planning and executing the investigation. The entire technical process calls for a well-knit team under the guidance of a doctor who focuses it according to the clinical picture. The result must be interpreted with extreme care; yet despite these precautions there are bound to be some errors of interpretation in the initial period of CT application, especially regarding the nature of the disease.

Conclusions

Since the advent of CT an agreement has been reached with our neuro­logist, otologist and neurosurgeon colleagues on the following neuro­radiologic agenda for patients with a cerebellopontine angle syndrome:

1. Plain X-rays of the skull with detailed study of the petrous bone regions;

2. Complex multidirectional tomography of the petrous bones with special reference to the internal auditory meatus;

3. CT.

If the CT is positive, we seldom resort to other, contrast, investi­gations. If the CT is doubtful regarding the nature of the lesion, angiography is indicated; but if there is doubt as to the existence of a lesion, pneumoencepahlography should be done first and then, if there is still doubt after PEG and CT, a contrast study of the meatus should be carried out. Finally, if the investigations require surgery, systematic follow-up with CT on discharge and at intervals afterward are necessary.

82

Bibliography

FAWCITT, R.A., ISHERWOOD, I.: Radiodiagnosis of intracranial Pearly Tumours with particular reference to the value of computer tomography. Neuroradiology ~, 235-242 (1976)

GREPE, A., GREITZ, T., NOREN, G.: Computer cisternography of extracerebral tumours using lumbar injection of a water-soluble contrast medium. Acta Radiologica (Suppl.) 346, 51-62 (1975)

GYLDENSTED, G., LESTER, J., THOMSEN, J.: Computer tomography in the diagnosis of cerebellopontine angle tumours. Neuroradiology 11, 191-197 (1976)

KENDALL, B., SYMON, L.: Investigation of patients presenting with cerebellopontine angle syndromes. Neuroradiology ~, 65-84 (1977)

NAIDICH, N.E., LIN, J.P., LEEDS, N.E., KRICHEFF, 1.1., GEORGE, A.E., CHASE, N.E., PUDLOWSKY, R.M., PASSALAQUA, A.: Computed tomography in the diagnosis of extra­axial posterior fossa masses. Radiology llQ, 333-339 (1976)

SALVOLINI, U., MENICHELLI, F., PASQUINI, U.: L'intered de la Console d'examen EMI. J. Neuroradiol. -l, 215-220 (1976)

83

Fig.l. Megadolichobasilar artery with ectasia and tortuousness affecting the left cerebellopontine angle region

Fig. 2. Large aneurysmal sac (PICA) in the left cerebellopontine angle; top: before administration of contrast medium the sac is seen to be partly filled with clots; bottom: after administration of contrast the small vascularized portion becomes visible

Fig.3. Large angioma of the left half of the posterior fossa

Fig.4. Neurinoma of the left cerebellopontine angle, barely detectable at the level of the cistern of the angle, which is dilated and occupied at the center. Deform­ation of the fourth ventricle with backward deviation of the left lateral recess

Fig.5. Intracanalicular neurinoma reaching the level of the acoustic pore; widening of the left internal auditory meatus

Fig.6. Neurinoma of the right acoustic nerve: its intracanalicular portion and extra­canalicular development together with the widening of the meatus are clearly visible

Fig.7. Extracanalicular neurinoma of the left acoustic nerve: hypodense before (left) and hyperdense after administration of contrast medium (right)

86

Fig.B. Large neurinoma of the right acoustic nerve: note the cranial extension and the connections with the tentorium

Fig.9. Cystic neurinoma of the right acoustic nerve

Fig.10. Hypodense neurinoma of the left cerebellopontine angle with dilation of the internal acoustic meatus; no change after contrast

Fig.ll. Recklinghausen's disease (neurofibromatosis) with locations in both cere­bellopontine angles and at the level of the right orbit

87

Fig.12. Epidermoid cyst in the left cerebellopontine angle: note the central hypo­density, the multi lobate appearance and the hyperdense rim after intravenous ad­ministration of the contrast. The view through the temporal horns (below) shows the connections between the supratentorial development on the left and the tentorial

notch

Fig.13. Epidermoid of the right ce­rebellopontine angle with subtentorial development; before (top) and after (bottom) intrave­nous injection of the contrast medium

90

Fig.14. Extensive epidermoid below and above the tentorium; margins blurred

Fig.iS. Meningioma of the left petrous bone developing into the cerebellopontine angle. Modest hyperdensity before (top left) and more marked density after administration of contrast

91

Fig.16. Psammomatous meningioma of the tentorial notch extending as far as the right cerebello­pontine angle

Fig.17. Meningioma of the left middle fossa with enormous hyperostosis extending as far as the petrous bone; intratumoral calcifications

92

Fig.18. Meningioma of the tentorium (inferior aspect) extending into and occupying the right half of the posterior fossa; note the anterior vascular pedicle

Fig.19. Enormous meningioma of the left half of the posterior fossa, partially ~

calcified: note the irregular hyperostosis at the level of the left occipital in­sertion

93

A

B

94

Fig.20. Meningioma extending from the cerebellopontine angle toward the clivus and tentorial notch on the right

95

Fig.21. Meningioma extending from the craniospinal region as far as the tentorium on the left: below we see the study of the skull and occipital foramen within which the tumor mass can be detected

96

Fig.22. Left glomus jugular tumor: erosion of the bone of the base at the left of the jugular foramen, with irregular fleshy mass occupying also part of the external auditory meatus; irregular calcification at the level of the homolateral cerebello­pontine angle

97

Fig.23. Encapsulated tumor (of unidentified histology) extending from the left cerebellopontine angle forward toward the prepontine cistern, the crural cistern and the interpeduncular cistern on the left

Fig.24. Partially excavated metastasis from mammary carcinoma located inside and outside the cerebellum on the right

98

Fig.25. Nasopharyngeal sarcoma extending in a cascade toward the intracranial structures, occupying the left cerebellopontine cistern

Fig.26. Outcome of complete surgical removal of left acoustic neurinoma by trans­mastoId and occipital approach. No recurrence

99

Fig.27. Outcome of removal of left cerebellopontine angle neurinoma, with definite postsurgical atrophy. No recurrence

Fig. 28. Outcome of partial removal of right mycotic abscess: clearly remains with intense perifocal edema

100

Fig.29. Outcome of removal of neurinoma of the left cere­bellopontine angle

Fig.30. Outcome of intracapsular removal of neurinoma of the left cerebellopontine angle

Fig.31. Outcome of partial resection of neurinoma of the left cerebellopontine angle

Fig.32. Recurrence of operated meningioma of the left petrous bone

102

Fig.33. Remains of meningioma of the inferior aspect of the tentorium after partial resection

Fig.34. Recurrence of operated epidermoid: the hypodense formation extends toward the right from the cerebellopontine angle region, forward to the clivus and upward beyond the tentorial notch

103

Fig.3S. Recurrence of epidermoid cyst on the right: thin hyperdense rim after ad­ministration of contrast medium, but content isodense

The Cervical Medullar Canal and its Content P. Manes and W. van Damme

CT exploration of the spinal cord consists of studying the spread of densities at the level of the content of the cervical canal. Since the spinal cord has rather small dimensions its direct study on the oscillographic screen and, a fortiori, on polaroid film is almost im­possible.

Using a CT slice of a cervical vertebra stored on floppy disk which can be read in and processed by a number of different programs, we have studied different ways of displaying the original data.

Beside screen display and polaroid pictures, the research program of the computer allows the following methods of CT slice analysis.

1. Numeric representation of a part of the CT slice presented gra­phically, localized on the spinal cord by means of a reference program ("REPERE").

2. Printout on a 1:1 scale of the CT slice. 3. Magnification printout of the spinal canal and of its content. 4. Profile of the CT slice around a line passing through the spinal

cord. 5. Histograms of the medullar canal and its content. 6. Magnified polaroid pictures of the medullar canal. 7. Study of isodense lines on polaroid film reflecting the cervical

canal and its content at different degrees of magnification.

The reference program ("REPERE") locates a place on the spinal cord by coordinates (x = column numeral, y = line numeral). In this way, it is possible to know the dimensions of the spinal cord by the number of lines and columns of the spinal canal and, more particularly, of the spinal cord. The scopic picture has a 128 x 128 matrix, with a definition of 128 lines and 128 columns. The cervical canal, for in­stance, is located between the 55th column and the 59th column and be­tween the 66th and the 72nd line. The graphic location (x,y) is x = 57 and y = 69 (Fig.1).

With the "SORNU" program a numerical expression of densities is ob­tained from 1/8th of the picture's surface at a point x = 57 and y = 69, showing that the densities of the medullar canal are spread between 187 and 216 (Fig.2).

With this information, the "FAX" program obtains a printed picture at a 1:1 scale on a matrix of 256 x 256, representing only the densities 187 - 216, which correspond to a CT picture of mean density 202 and with a window of 28 (Fig.3).

The "ZOOM" program provides a variable magnification degree either on scopic and polaroid picture or on a printout. This printout is ob­tained only after the window and the mean density are determined (Figs.4-6). For instance, at mean density level 202 printout and

polaroid pictures with various windows of 28 (Fig.7), 112 (Fig.8), 224 (Figs.9-11) have been implemented.

105

On these pictures, we then use the isodensity program ("ISOD") which gives greater brilliance to points of a chosen density. In each case we isolated the points of a density of 200, corresponding to the density of C.S.F. Depending on the case, density levels of 210 (Fig.7) or 225 (Figs.9-11) were also isolated and then translated on the polaroid picture into different tones of grey, depending on the chosen iso­density. The morphologic translation of the numerical printout allows a direct visualization of the density distribution at the level of the medullar canal, with the zones of highest density located central­ly and peripherally while zones of density below 200 are situated be­tween them.

The program "PROFILE" calculates the density of each intersecting point of a line and all of the columns of the scope picture, with the density level of each point varying of course according to the thick­ness of the slice (0.3, 0.6, 0.9 cm).

In Figure 12 a profile is aligned around the 69th line, which passes through the center of the medullar canal. At the center a peak in den­sities from 186 to 207 occurs, which is bordered by two symmetrically located peaks of bone density corresponding to the bony walls of the medullar canal.

The "HISTOG" program produces a histogram of the whole medullar canal (Fig.13), as well as the spinal cord (Fig.14), providing information on the distribution of the densities within a chosen volume, which depends on the thickness of the slice and its surface, which may also be selected. With a histogram four mean density levels may be stated corresponding to lipid tissue «200), to C.S.F. (200), to nervous tissue «207), and to the vascular pole (>208).

106

Fig.l

29728828' 202 1992882872 1221 .... 21-111 211 210220231:10 247 :tG.3 2.116244 22G 2ICJ 20a 20S 1110' 20.:1 287 286 213 21. 281S 217 280 280

287 217 2 .... 211 199 19' 281 :Z87 2lJ 213217 292 2" 21e :116 223 220 22:) 213 286 283 28a 2&1 28& 288 190 197 199 283 2" 28' 2&6

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Fig .14

Cerebral Ischemia Y. Palmers, B. Staelens, A. L. Baert, and L. Termote

In the pathology of the central nervous system, the ischemic cerebral lesions occupy a prominent position primarily due to their large num­ber. An exact knowledge of the extent and the location of the ische­mic process is indispensable not only for a complete diagnosis, but also for a well-founded prognosis.

CT examination in all cases of acute vascular pathology is currently considered indispensable. A differential diagnosis based only on cli­nical data can be difficult if not impossible, especially when an ischemic process, an intracerebral hemorrhage, a tumor which has bled, or an acute neurologic accident caused by a tumor must be differen­tiated.

In cases of cerebrovascular stroke, CT permits quick differentiation between an ischemic lesion and an intracerebral or extracerebral hem­orrhage, something of great importance for selecting the most appro­priate type of treatment. The CT examination in cases of intracere­bral hemorrhage must be performed both before and after an injection of contrast medium, because in some cases this double examination makes possible the visualization of the lesion responsible for the hemorrhage.

If the cerebral structures are considerably displaced, especially if surgical treatment appears indicated, then a cerebral angiography is necessary. However, if they are not displaced, the diagnosis of intra­parenchymatous effusion is made. At this point, it is better not to manipulate the patient any further and to follow the spontaneous evo­lution of the lesion.

In the case of an extracerebral hemorrhage, CT can determine its in­traventricular or meningeal nature, sometimes even visualizing the responsible anomaly. In the majority of cases, however, angiography remains the procedure of choice to clarify the exact cause of the hem­orrhage.

In cases of ischemic stroke, CT visualizes the extent of the ischemic area and illustrates the stage of evolution (edema, necrosis or pro­gressive organization, sequelae). Angiography should not be performed unless a surgical intervention is planned on the extracerebral arterial tree, which requires opacity in the carotid and vertebral stem.

Interpretation of CT images is based on the topographic modification of the different cerebral structures as well as on the specific changes in radiodensity.

This paper mainly deals with the classic cerebral infarction without alluding to rare cases such as Binswanger's disease. Neither the la­cunar infarct nor the hemorrhagic infarction is extensively discussed, and the anatomopathologic aspects of the ischemic process are also generally omitted.

114

The different appearances of an ischemic lesion, depending on its evolutionary stage, can be summarized as follows:

1. Stage I: the stage of acute and dramatic clinical signs lasts up to 5 - 12 h after the cerebrovascular accident. The CT image shows no clearly pathologic sign.

2. Stage II: the stage of important morphologic changes starts be­tween 5 - 12 h after the onset of the ischemic accident and lasts about 2 months.

3. Stage III: the stage of sequelae or cicatrices starts from 2 - 3 months after stage I.

Stage I or the clinical stage

Since the CT examination is normal, cerebral angiography must be re­sorted to to show the lesions.

Stage II

After some hours (at least 12 h) CT visualizes the ischemic region as an area of decreased density. Initially the lesion, less than 24 hold, appears as a poorly defined, heterogeneous area of slightly decreased density, resulting from the edema. After 24 h, and even more clearly after a few days, the damaged zone in the majority of cases shows up on CT as a well-defined, homogeneous low-density area.

During this evolutionary stage neuronal necrosis begins, followed by local encephalomalacia, liquefaction of the necrotized tissue, and a glial proliferation forming a neuroglial scar. CT cannot identify or exclude petechial hemorrhages in the ischemic low-density area.

In some cases the initial image of a heterogeneous area of slightly decreased density persists for weeks or months and may even completely disappear. This heterogeneous aspect can be explained by the presence of very small, relatively undamaged areas in the ischemic region, which owe their existence to a locally accurate collateral circulation.

The edema and the inflammatory reaction often causes a mass effect: some large, recent infarctions mimic a tumoral behavior with dis­placement of cerebral structures. This phenomenon can be observed during the first 15 days, particularly during the first week.

A second phenomenon frequently seen in recent infarct is the uptake of contrast medium or contrast enhancement after intravenous injection, which causes an increase in X-ray absorption values in the involved territory. About 50 - 60% of the recent brain infarcts show contrast enhancement during a 4 week period following the ischemic stroke. The manner of contrast enhancement, though sometimes heterogeneous, is mostly homogeneous, and is unrelated to the extent, the form, the age or the location of the infarction.

The mechanism of this phenomenon of contrast uptake is highly complex: several factors playa role, such as:

1. The blood-brain barrier, when changed by metabolic acidosis, re­sults in an increase in capillary permeability.

2. The increase in size of the capillary network results from the lack of local vascular autoregulation.

3. The phenomenon of "luxury perfusion," i. e., the increase in non­nutritional circulation at the level of the ischemic lesion, is caused by cortical vasoparalysis and possibly also by small AV fistulas. This phenomenon occurs only when the obstructed artery can restore its permeability, and this has never been visualized by angiography later than 14 days after onset of hemiparesis.

115

Among the several types of contrast enhancement it has so far been impossible to correlate any type of contrast uptake with a specific etiological factor or with a well-defined prognosis. The manner of contrast enhancement can be heterogeneous and fingerlike (especially in the cortical region, where it is possibly related to the phenome­non of luxury perfusion), spotted, or homogeneous over the entire low-density zone. In the latter case the area of decreased absorption becomes less hypodense, sometimes even becoming isodense and disap­pearing completely on the postcontrast CT images. This means that a cerebral CT examination only after injection or infusion of contrast medium may lead to false negatives.

Approximately 50 - 60% of brain infarcts between 1 and 4 weeks old may be enhanced by contrast material. The degree of contrast uptake is often most striking during the second week. We have never been able to observe a clear increase in density of the ischemic area on the postcontrast CT image made two months after the onset of the ce­rebrovascular accident. A contrast uptake in 20 - 30% of the cerebral infarcts had already been exhibited during the first week.

Among the patients who show contrast enhancement, the infarcted, low­density region becomes a partially high-density area in 60 -70% of the cases (according to different authors); in 25 - 40%, the hypo­dense area becomes less hypodense or even disappears completely. In some patients we found a localized contrast uptake on the postcontrast images, whereas the precontrast CT examination was normal. Thus, more evidence is provided for a cerebral CT examination without con­trast medium leading to false negatives.

Stage III (= stage of the scars or sequelae)

After a variable period (2 months or more), the necrotized cerebral tissue is replaced by a liquid material with an absorption value very similar to that of cerebrospinal fluid. The softened area of encepha­lomalacia becomes cystic; its margins are regular and smooth now and its density values approximate those of the ventricular cavities. The overall accuracy of CT for detecting brain infarcts at this stage is very high and diagnosis is mostly no problem: in 50 - 60% of the cases there is a localized widening of the neighbouring ventricular struc­tures, with or without attraction of midline structures. The extent of brain tissue loss depends upon the importance of the obstructed artery, but the duration of the ischemia and the activity of the collateral blood supply also play an important rule. At this stage there is no longer any evidence of contrast enhancement.

Small peripheral infarctions usually have the shape of a triangle or a wedge whose base faces the cortex.

In an exceptional case, an atrophic postnecrotic calcification appears in the damaged area. This phenomenon was observed in a patient who showed, eight months prior to the second examination, a CT image of a brain infarct with a hemorrhagic component.

116

It is necessary to mention in this context the great discrepancy be­tween the remaining clinical signs and the morphologic sequelae. It is absolutely impossible to estimate the neurologic condition of a patient by analyzing the CT images of his brain.

In a minority of the cases, an infarcted low-density area either dis­appears completely or persists for months or even years as an area of slightly decreased absorption values. Most of these cases are small infarcted zones with intensive glial proliferation or a collateral circulation sufficient enough to permit an almost total morphologic restitution.

As far as etiologic factors are concerned, CT does not furnish any information, but here clinical data can give some additional informa­tion, such as signs of arteriosclerosis, predisposition to embolism (atrial fibrillation), prolonged spasm, etc. Nevertheless, in a few patients CT can visualize the cause of the ischemic process; e.g., a large aneurysm which has embolized the territory of its artery or an AV malformation which has insidiously caused an ischemia of an extend­ed area during a sudden and prolonged decrease in arterial blood pres­sure.

The distribution of ischemic processes can be summarized as follows (the percentages vary according to the different authors):

1. The territory of the middle cerebral artery: 76 - 81%. 2. The territory of the posterior cerebral artery: 14 - 20%. 3. The territory of the anterior cerebral artery: 1 - 4%.

The importance of recognizing the vascular topography of edematous areas and becoming more familiar with transverse axial representation of the vascular distribution of the brain must be emphasized, espe­cially since the angle of the cuts is always merely approximate, varying from one patient to another and thus making it extremely difficult to locate precisely an edematous area on the arterial geo­graphic map.

Also worthy of mention is the enormous disproportion which often exists between the territory of the obturated artery and the extent of the damaged area, the latter usually markedly smaller than the former. For example, several cases of occlusion of an internal carotid artery presented on CT a more or less extensive area of decreased den­sity in the territory of a sylvian artery. Yet two patients known to have thrombosis of an internal carotid artery were examined several times by CT, and all the performed CT images were considered normal. This phenomenon can be explained by the great variety in activity of the collateral blood supply.

In the posterior fossa the evolution of the CT image of an ischemic process is similar to that of a supratentorial infarct.

While the detection of a hypodense zone in the brain stem remains dif­ficult with our present X-ray scanners, the diagnosis of a hemorrhagic infarction of the brain stem is much easier with the CT image, parti­cularly if sufficient information concerning the clinical history of the patient is available.

The extra-axial hermorrhagic infarct differs from the classic intra­cerebral hemorrhage in that in the former the blood is concentrated (mostly eccentrically) in a relatively large area of decreased den­sity ; whereas in the latter the accompanying edema is minor and

117

forms a tiny ringlike hypodense area around the blood mass. In the majority of cases the hemorrhage occurs 4 - 6 days after the onset of the ischemic stroke (after the breakdown of the blood clot) and appears on CT as a hyperdense zone at the periphery of the hypodense infarcted area.

Finally, some considerations must be devoted to the differential diagnosis. A precontrast low-density area which provokes shifting of the surrounding cerebral structures and which shows contrast enhance­ment is likely to be a tumor. However, clinical history is indispensable for the differential diagnosis, and every case must be studied indi­vidually.

In the case of cerebral infarction, nevertheless some characteristics seem quite specific:

1. A triangular zone of decreased absorption values or a low-density area corresponding to the territory of a cerebral artery.

2. A low-density area which extends also into the cortical region. 3. A large and homogeneous area of decreased density. 4. Sometimes the type of contrast enhancement favors the hypothesis

of an infarct, e.g., low-grade and homogeneous contrast uptake, or fingerlike high-density areas on the postcontrast scan.

But generally, the differential diagnosis requires: first, the know­ledge of the clinical history of the patient (as mentioned earlier) and second, a repeated CT examination after a few weeks, which will almost always resolve doubts.

An ischemic lesion either evolves to the cystic or porencephalic stage and loses the property of contrast enhancement, or else dis­appears completely. The differential diagnosis must distinguish between a brain infarct and several other pathologies such as a glioma, as a solitary metastasis and sometimes also an inflammatory or infectious lesion, a demyelinizing disease, a focal atrophy and sequelae of an intracerebral hemorrhage.

Identification of the vascular distribution of a given edematous area is very important for the differentiation between an ischemic lesion and a tumoral lesion, because gliomas and metastases on the precontrast image and even quite often on the contrast CT image also can show a low-density pattern caused by the accompanying edema and very similar to the pattern of an ischemic lesion. In infarcts, however, the low­density area frequently extends into the cortical region. In general, the mass effect of an infarct is less marked than that of a glioma or a metastasis, but multiplicity of these areas of decreased density favors the possibility of metastasis. Nevertheless, the clinical his­tory and particularly the evolution of the CT image during repeated examinations over a few weeks together elucidate the exact nature of a lesion which was doubtful initially.

Inflammatory and infectious lesions can also pose differential diag­nostic problems, especially in cases of localized cerebritis. The CT image of demyelinizing diseases and of focal atrophy can be identical to that of an older brain infarct, but the clinical picture of these two groups of cerebral affections is completely different. Finally, the morphologic sequelae of an intracerebral hemorrhage and of an infarction are generally very similar, but from a strictly clinical point of view an etiologic differential diagnosis is rarely indis­pensable.

118

Conclusions

To repeat a few important points:

A CT image should not be interpreted without clinical data. A CT examination should always be performed both without and with contrast injection. After a few weeks, repeated CT examination is extremely useful in resolving differential diagnostic problems.

We acknowledge the precious aid of Dr. G.A.J. TOPS for the trans­lation into English.

Bibliography

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119

A B

Fig.1. Ischemic lesion stage II. A. Patient M.O. Less than 24 hours after the on­set of the cerebral attack. Notice the poorly defined area of slightly decreased density in the territory of the right sylvian artery. B. Patient V.M. 36 hours after the onset of hemiplegia of the right side. The low-density area in the left temporal region is more clearly discernible with a more homogeneous aspect and sharper margins. The left ventricular body is no longer visible

A B

Fig.2. Infarction stage II. Patient V.L. Four days after the first acute clinical signs. Large, homogeneous and well-defined zone of decreased absorption values on the left side; slight shift to the right of the midline structures with flattening of the left lateral ventricle and displacement of the choroid plexus. Angiography demonstrated a thrombosis of the left internal artery

120

Fig.3

Fig.3. Mass effect. Patient R.E. 5 days old infarction. Large low-density area, well demarcated in the territory of the right sylvian artery. Midline structures are shifted to the left with compression of the body of the right lateral ventricle

Fig.4. Types of contrast enhancement. A. Patient M.M. Ischemic stroke three days before visualization. Fingerlike contrast enhancement in the region of the right middle cerebral artery. B. Patient D.M. Acute thrombosis of the right sylvian artery (proved by angiography) ten days prior to enhancement. A small localized area of intense contrast uptake in the right temporal region. The third ventricle is stretched to the left and the right ventricular intersection as well as the ipsilateral posterior horn are compressed. The image is compatible with a tumoral lesion

B

D

Fig.5. Contrast enhancement. Patient V.A. A and B. Right occipital infarct. The area of increased X-ray transparency is clearly visible on the pre contrast CT image. C and D. After injection of contrast medium the involved area has completely disappeared from the image

A

C

A

121

B

D

Fig.6. Contrast enhancement. Patient C. A. Cerebral attack 8 days before. A and B. On the precontrast images the only pathological features discernible are signs of a minor cortical atrophy. C and D. The postcontrast CT pictures reveal a left frontal enhanced area. Angiography did not reveal any obvious anomaly

B c Fig.7. Stage III (cystic or porencephalic stage). A. Patient D.C. 3-month-old infarction. Left frontal low-density area: its density approximates that of cere­brospinal fluid. Dilatation of the left anterior horn and slight shifting of the midline structures to the involved side. B. Patient G.I. Infarction about 4 months and 3 weeks old. More widely extended lesion than in the former case. Huge dilata­tion of the left lateral ventricle. Absorption value of involved area is quite similar to that of ventricular space but no communication with ventricular system. C. Patient V.N. Large porencephalic cyst in the right temporoparietal region com­municating with the ventricular system

122

A B

Fig.8. Aneurysm. Patient S.R. Images after contrast enhancement. A. Right-sided paramedian spot with intense contrast uptake. (Angiography confirmed the presence of a large aneurysm of the right middle cerebral artery.) B. Considerable enlarge­ment of the right lateral ventricle, with the ventricular body. In the temporo­parietal region we can see a low-density area with a heterogeneous fingerlike con­trast enhancement. These images correspond to ischemic lesions in different evo­lutionary stages. The aneurysm has embolized the territory of its artery

A B

Fig.9. Arteriovenous malformation. Patient L.J. Examination before (A) and after (B) injection of contrast enhancement. The huge A.V. malformation is best visualized on the postcontrast pictures: The anomaly has insidiously caused an ischemia in a large left frontotemporal region corresponding to the large focus of atrophy at that level

123

A B

Fig.10. Infarct of the posterior fossa. A. Patient P.J. Ischemic process, 4 days old. Notice the low-density area on the left aspect of the posterior fossa: ischemia in the territory of the superior cerebellar artery. B. Patient S.M. Ischemic pro­cess, about three weeks old. A triangular area of decreased density in the left in­ferior part of the posterior fossa, occupying the territory of the posteroinferior cerebellar artery

A B

Fig.ll. Central infarction. Patient V.D.C.S. A. Before injection of contrast medium. B. After injection of contrast medium. In the right thalamic region a round low-density area shows contrast enhancement particularly at its margins. Evolution and clinical history favored the hypothesis of an ischemic lesion

124

A B

Fig.12. Hemorrhagic infarction. A. Patient G.L. Hemorrhagic infarction in the right temporal region. Low-density area in the right temporal region, which in­cludes an intraparenchymatous hemorrhagic area (at the level of the external cap­sule). B. Patient H.M. Hemorrhagic infarction of the brain stem. The brain stem (particularly the right part) shows an increased absorption value; surrounding ce­rebellar tissue has a lowered density. This patient suffered from severe vertebro­basilary insufficiency

A B

Fig.13. Characteristics of a classical infarction. A. Patient H.A. 3-month-old infarction. Triangular low-density area in the right parietal region. B. Patient M.J. 9-day-old infarct. Small wedge-shaped radio transparency in the left frontal lobe

125

A B

Fig.14. Characteristics of a classical infarct. A. Patient L.G. Three days after the onset of hemiplegia. Homogeneous low-density area extending into the cerebral cortex. B. Patient D.C. About 30 hours after a cerebral attack. Large low-density area occupying the vascular distribution of the right sylvian artery

A B

Fig.1S. Characteristics of a classical infarct. Patient L.G. Evolution of the right temporal ischemic lesion in the same patient. A. Stage II (after 3 days): Well-defined low-density area, with slight flattening of the right anterior ven­tricular horn. B. Stage III (after 4 months): Involved area has diminished in size and presents a still lower absorption value. The ipsilateral frontal horn is clearly wider

126

A B

Fig.16. Differential diagnosis. Patient V.M. Metastasis of a Ewing sarcoma. A. precontrast image shows a low-density area in the territory of the left posterior cerebral artery. The ipsilateral calcified choroid plexus is slightly displaced forward. This image suggests an ischemic lesion. B. The postcontrast image is quite specific for a metastasis and excludes the vascular hypothesis

A B

Fig.17. Differential diagnosis. Patient R.M. Metastasis of a breast cancer. A. Before contrast enhancement: Large heterogeneous area of decreased density, with­out vascular distribution and without extension into the cortex and considerable shifting of the midline structures. The image suggests a tumoral lesion. B. After injection of contrast medium: The bifocal contrast uptake is very typical of metas­tasis

A

c

127

A B

Fig.1B. Differential diagnosis. Patient G.L. Metastasis of a breast cancer. A. Precontrast picture. B. Postcontrast picture. A huge left temporo-occipital zone of decreased density without obvious vascular distribution does not enhance after injection of contrast medium. Notice also the marked shift of the midline structures to the opposite side and the considerable forward and inward displace­ment of the choroid plexus. An image like this does not suggest an ischemic lesion

B

o

Fig.19. Differential diagnosis. Patient V.A.M. Glioma (relapse). A and B. Before injection of contrast medium. Extended heterogeneous area of decreased density in the left temporoparietal region. Marked shifting of the midline structures to the right and complete compression of the left lateral ventricle. The image suggests an expanding rather than an ischemic process. C and O. After injection of contrast medium. An irregular ringlike enhancement in the center of the area described above and a low-density whorl remaining around it

Cerebral Metastases J. C. Dosch

Any neurologic symptom occurring in a patient with a neoplasia raises suspicion of a metastasic lesion. Tomodensitometry can usually dis­close the metastasic nature of the lesion, delineate precisely its location, extension, isolation or multiplicity, and define the im­portance of the perilesional edema. Conversely, the tomodensitometric diagnosis of a cerebral lesion supposed to be of metastasic origin can lead to complementary investigation to discover the primary neo­plasia.

In current practice, the aim of tomodensitometry in neoplastic patho­logy is twofold: either to verify the metastasic nature of the lesion or to disclose an associated pathology', as is frequently the case in cancer patients. Two etiologies seem to predominate: first, vascular etiology due to the advanced age of the patient and second, infectious pathology, favoring abscesses because of the low defense reactions and aggravated by the antimitotic and immunodepressive medicines as well as the opening of invasion routes for treating the primary neo­plasm.

Analytic Data in Cerebral Metastases

Metastases appear as lesions with mixed density from the very begin­ning - hypodense and hyperdense parts here are considered separately.

Hypodense or Edematous parts

Prior to Injection

Edema encircles the metastasis, thus allowing visualization of its borders. Spread over several sections, it looks like a geographic map with well-defined demarcations from the normal cerebral paren­chyma. The tomodensitometric distribution over 2 - 3 density levels shows the homogeneous pattern of hypodensities, confirmed by our iso­density option.

After Injection

No changes occur in the shape of the lesion or in the distribution of its densities, whichever level is considered. The hypodense area de­limited by the edema remains unchanged in distribution and in mor­phology, independent of the contrast infusion.

129

Hyperdense or Tumoral parts

Prior to .Injection

Isodense with regard to the cerebral parenchyma, the density level of the hyperdense metastases is never higher than that of the peri­cerebral gray matter and the density value increases from the peri­phery toward the center. It is visualized as a round, solid tumor without intratumoral necrosis.

After Injection

The usually only moderate increase of density is nevertheless suffi­cient to allow a precise outline of the tumoral area. However, the ratio between the tumoral and the edematous surfaces prior to and after contrast infusion remains unchanged (Figs.2-4; 6-8). This characteristic feature differentiates metastases from primary tumors, which are characterized by an increased ratio between the hyperdense and hypodense volumes.

Summary

The density of an edema is not influenced by IV perfusion. Metastases are generally isodense with regard to the cerebral parenchyma. IV per­fusion does not modify the ratio between the volume of hyper- and hypodense areas in the tumoral area, although the density of metas­tatic tissue increases.

Fig.1 Fig.2

Figs.1-4. Metastasis of an epithelioma of the lung, prior to (1,2) and after (3,4) infusion of contrast

medium

130

Fig.3

Fig.5

Fig.7

Fig.4

Fig.6

Fig.8

Figs.5-8. Metastasis of an epithelioma of the lung, prior to (5,6) and after (7,8) infusion of contrast

medium

Inflammatory Diseases of the Brain M. G. Dupont, L. L. Morteimans, D. Baleriaux-Waha, A. Bollaert, and L. Jeanmart

Our study involves 56 .observations on inflammatory diseases of the brain, the basis for which are 69 tomodensitometric examinations made on patients age 7 months to 64 years during the period May, 1976 -February, 1977. The "Delta-Scan" with a matrix of 256 x 256 was used, and all the examinations were systematically practiced with and with­out intravenous injection of contrast medium.

In the acute or subacute stages of the inflammatory process, the in­vestigations were practiced between the 2nd and 30th day. Only those patients were examined who exhibited an aggravation of their clinical state, e.g., clouding of consciousness, appearance of focalization, and in a few particular cases, a blockage of the CSF circulation veri­fied by isotopic cisternography, all patients suffering from menin­gitis or encephalitis were not examined. The existence of an important alternative to EEG and epilepsy, sometimes arising during the treat­ment in the chronic or sequelae stage, justified the research.

Acute or Subacute Meningitis and Brain Abscesses

Among the 20 patients with acute or subacute meningitis examined by CT, nine showed one or several brain abscesses. The clinical data of the following cases will illustrate our observations and CT-findings.

R.G. 31 years old, male, was admitted with all signs of acute menin­gitis. After 8 days of antibiotic treatment, the patient still exhi­bited signs of meningism, frontal headache and photophoby. The CT applied on the 11th day after their manifestation reveals a dilatation of the ventricular system concentrated in the 3rd and the lateral ven­tricles, especially on the level of the frontal horns, which present blunted angles. After injection of iodine contrast (140 ml Contrix 28), areas of increased density, unrestricted and disseminated, appear in the brain (Fig.1A). After one month, the patient feels better, and both his CSF and EEG signs are again normal. Moreover, CT shows that the ventricular system is normal, and the areas of heterogeneous den­sity are no longer recognizable (Fig.2B).

P.V. 27 years old, male, is hospitalized due to SUsp1c1on of brain abs­cess. CSF is purulent, and a clouding of consciousness with disorien­tation and agitation is followed by hemiparesis of the left side. CT applied on the 3rd day after the onset of the illness shows a dis­placement of the frontal horns to the left with a large area of de­creased density in the right frontal lobe and the right occipital horn is no longer recognizable. After injection of contrast media, the CT shows a margin of increased density next to a subdural area of de­creased density in the parietal and frontal cortex (Fig.2). Surgery reveals a large subdural empyema, and an important edema is also pre­sent in the frontal lobe but no abscess at this level. Among three

132

patients examined between the 4th and 9th day of the illness, narrow­ed ventricles were found, and the subarachnoid ian spaces were not re­cognizable, thus corroborating the description SCHNEIDER et al. (2, 372-377).

D.R.L., 35 years old, male, after operation for chronic mastoiditis shows several signs of meningitis. The CT shows a lateral displacement of ventricles to the right with narrowing of the left ventricle. The cut at the level of the left mastoid shows a fistula with a hyperdense area in front of it. The area of decreased density occupies the tem­poral lobe. After the injection of contrast media a small margin of increased density surrounded by an edema is revealed (Fig.3).

The patient was treated by puncture, and a purulent CSF was found. The CT diagnosis of abscess was thus verified.

D.P~ 46 years old, male, consults doctor for ocular disturbance. In his case history cachexia, pulmonar bronchiectasis, and treatment for tuberculous meningitis several months prior are noted. The CT shows a significant dilatation of the lateral ventricles and a hypodense area in the left occipital lobe. After injection of iodine contrast, a high-density ring-shaped margin appears in the occipital lobe with perifocal edema. Another area of high density is also found in the right occipital lobe (Fig.4). Due to his bad clinical state and weak neurologic symptomatology, the patient is treated with wide­spectrum antibiotics, and controls are applied for 2 and 5 months after the first scan. These controls show a decrease in volume of the left cerebral abscess and total disappearance of the right abscess.

Other observations on brain abscesses shown by tomodensitometry: two patients had undergone a cranial traumatism. One, having suffered a backlash, had a depressed fracture of the skull, a subdural hematoma, and an important cerebral bruise. An abscess developed within the three weeks following the operation for traumatism.

Comments

The ventricular system in purulent meningitis presents a variable as­pect; sometimes it is narrow with an impression of periventricular edemas, as SCHNEIDER (2) describes it, and sometimes it is dilated, as demonstrated in three of our cases.

The most frequent densitometric sign met in our series is the hetero­geneous aspect of the white substance following injection of iodine contrast. Vaguely defined hyperdense areas are observed which seem to correspond to localized hyperemia areas. Thanks to the tomographic controls, the explanation of an abscess in formation may be rejected.

The characteristic aspect of cerebral abscess in axial tomography is that of low-density area in which the regular or lobulated outlines of a hyperdense ring appears after injection of iodine contrast. This ring, located in the middle of an edematous area, defines a center of weak density. Sometimes there may be several. The differential to­modensitometric diagnosis of an abscess, a necrotized tumor, and a metastasis is difficult; the anamnesis and the clinical data are in­dispensable for establishing the final diagnosis.

Tuberculous Meningitis and Tuberculoma

Ten patients were examined at the acute stage of the illness, among which three tuberculomas were verified.

133

F.G., 31 years old, male, had had a tuberculous meningitis for 3 weeks when he was examined with CT Scan for serious headaches and a persis­tent frontotemporal alteration on EEG. Significant dilatation of the ventricular system concentrating in the 3rd ventricle and the lateral ventricles is shown to exist. After injection of iodine contrast, areas with increased density and blurred outlines appear disseminated in the cerebral tissue. A slight increase of the density at the peri­phery of the ventricles is also noted. The choroidal plexuses are asymmetric, the left plexus appearing thicker than the right (Fig.5).

A tomodensitometric control made 2 months after the first examination confirms that the dilatation of the ventricles has retrogressed and that areas with heterogeneous density have disappeared.

K.A., 26 years old, male, was in a semicomatose state when he was ad­mitted. He presents papilloedema on both sides and diffuse "theta" activity on EEG. CSF contains 1.28 g/1 proteins, 400/3 cell (70% lym­phocytes), 0,25 g/1 glucose. The patient also exhibited hyponitremic symptoms (124 mEq/1). The diagnosis of tuberculous meningitis is veri­fied; no bacillus of Koch is found at the level of the spinal fluid. After 2 weeks of specific treatment, the patient remains confused and disoriented; he answers only to simple questions, the back of the eye remains unchanged, and Babinski's sign appears on the left side. Ap­plied 3 weeks after admission CT shows a dilatation of the 3rd ven­tricle and the lateral ventricles; an area of low density may be noted at the periphery of the right frontal horn (Fig.6A). Following injec­tion of the iodine contrast, a hyperdense irregular ring appears in the middle of this edema area (Fig.6B). On the basis of the tomodensi­tometric diagnosis of tuberculous abscess an operation is performed which reveals a solid mass at the bottom of the middle cerebral artery which was impossible to resect because of the multiple adherences. The anatomopathologic examination ascertains the tuberculous nature of the lesion.

The patient died 2 months after the operation due to bronchopneumonia and was not examined post mortem.

I.G., 15 months old, male, is admitted because of high temperature and vomiting. A tuberculin test was positive 5 months before, and an anti­tuberculous treatment was started. Upon his admission, he was sleeping and a discrete right hemiparesis existed. The spinal fluid shows 1,54 g/1 proteins, 0,12 g/1 glycorachy and 133 cells/mm3.

A CT Scan is made during the 3rd day of hospitalization; the ventricles are widely dilated, and a hypodense area outlines the left frontal horn. After the injection of iodine contrast, a hyperdense area not very well restricted appears on the outside temporal region. (Fig.7A). On the 27th day of hospitalization a right hemiparesis SUbsists as does a perturbation of the CSF formula (6 I leucocytes/mm3, 0,80 g/1 proteins). After the injection of the iodine contrast the tomodensito­metric control shows a small curved, hyperdense spot localized outside the left frontal horn, very likely at the level of the head of the caudal nucleus. (Fig.7B)

S.v., 9 years old, female, exhibited a typical tuberculous meningitis with fat acid bacillus resisting at the CSF's level 9 months before

134

her admission, at that time undergoing treatment. Upon her admission the child shows a right frontal focus of polymorphous waves "theta" and "Delta" on EEG. The CT shows a right frontal hypodense area dis­charging into the lateral ventricles on the left.

After injection of iodine contrast, a hyperdense nucleus of approxi­mately 4 cm of diameter appears, located at the periphery of this edematous area. The diagnosis of tuberculoma was verified, and during the operation and adhering mass at the dura mater was excised. Upon the histologic examination, centers of casal necrosis outlined lym­phocytary infiltration areas.

Comments

At the acute stage of tuberculous meningitis the lateral ventricles very often appear quite dilated. The injection of iodine contrast shows in most of the cases hyperdense areas, disseminated in the ce­rebral tissue and with blurred limit (Fig.8). The tomodensitometric image of the tuberculous aspect or of the tuberculoma is similar to the one of cerebral abscesses previously observed. The tomographic diagnosis is also oriented by anamnesis and clinical data. Thus patho­logic anatomy verifies the tuberculous nature of the lesion.

Encephalitis

Three patients were examined at the acute stage.

V.R., 4 years old, female, unconscious and feverish upon admission. No neurologic sign of focusing exists, and examination of the eye re­veals a papillary fuzziness. Radiography of the skull shows no sign of intracranial hypertension, while the left carotidian arteriography made due to important alterations of EEG reveals a slight vertical displacement of the middle cerebral artery with avascular area at the temporal level.

Axial tomography is practicea on the 3rd day of the disease: the ven­tricular system is recognized but only with great difficulty because the lines are not visualized and an area with lower density exists in the left frontal temporal region. After injection of the iodine contrast, this hypodense area is found more clearly (Fig.9).

LCR ascertains the assumption of the encephalitis diagnosis verified on the examination. Unfortunately the child died 5 days after her ad­mission and was not examined post mortem.

Two other cases of encephalitis also showed a decrease of the volume of the ventricular system and of the areas with heterogeneous density which is, however, less important at the level of the cerebral tissue.

V.G., 4 years old, male, showed a herpetic encephalitis a year before. A necrosis sUbsists of the entire temporal lobe and of the frontal lobe which were excised. The LCR shows a high percentage of antiherpetic antibody. Currently the child exhibits an important psychomotor back­wardness.

The CT scan reveals the importance of the encephalitis sequelae, a softening of the cerebral lobes with dilatation of the lateral ven­tricles and the presence of calcifications in the occipital lobe. Im­portant areas of fluid density are found at the periphery which cor-

135

respond to subarachnoidian dilated spaces (Fig.10). This picture was confirmed by gazeous encephalography.

Sequelae of the Cerebral Meningeal Infections

After the initial stage of cerebral infection 23 patients were examin­ed by tomodensitometry with delay periods of 5 months - 8 years. Most of the examinations were justified by an epilepsy and an important change of EEG. We previously stated the discovery of a tuberculoma and the important change after herpetic encephalitis. The most frequent tomodensitometric discovery by those patients, especially by those who exhibited an encephalitis, is the presence of a cerebral atrophy which may either be generalized with dilatation of the ventricles or else be localized by a porencephalic area.

Discussion

Although we don't have a sufficient number of anatomopathologic com­parisons, some verifications seem relatively frequent and permit an approximate diagnosis of the cerebro-meningeal infection.

It seems to be important at what time the examination is made in com­parison with the evolution stage of the infection. At the beginning of the cerebral infection the volume of the ventricle seems to reduce, probably secondary to a cerebral edema; this sign is most frequent in encephalitis. The dilatation of the ventricular system that is visua­lized at early or later stages may perhaps be explained by the block­age of the bottom cisterns or by the peripheral resorption as was shown by isotopic cisternography in cases 1, 2, 3 of tuberculous me­ningitis.

Another symptom continously observed is the presence in the cerebral substance of hyperdense areas not appearing very well defined after the injection of iodine contrast. These areas, however, do not neces­sarily correspond to abscesses in the making because the tomographic controls made during the cure show their return to a standard density of the cerebral substance.

Finally, it is useful to emphasize the difficulty of diagnosing cere­bral abscess by the standard neuroradiologic examination. The TAC based on an anamnesia and on suggestive clinical symptoms permits the diagnosis of cerebral abscess. Axial tomography also controls the evo­lution of inflammatory infections and their sequelae.

Bibliography

KRAMER, R.A., JANTOS, G.P., PELSTEIN, G.: An approach to contrast enhancement in computed tomography of the brain. Radiology ~, 641-647 (1975)

LANKSCH, W., KAZNER, E. (eds.): Cranial Computed Tomography. Berlin-Heidelberg-New York: Springer (1976)

LOTT, T., DA SILVA, R.F., REYNOLDS, J.P., EL GAMAL, T.: The value of CAT in brain abcess. Neuroradiology.2.! 273-285 (1975)

NEW, P.F.J., SCOTT, W.R.: Computer Tomography of the Brain and Orbit. Baltimore: Williams and Williams (1975)

136

Fig.! A Fig.! B Fig.2

Fig.!. A. Purulent meningitis with enhancement: ventricular dilatation. Area of high density dissiminated in the brain. B. One month later normal

Fig.2. Purulent meningitis: narrowing of the ventricular system displaced to the left. Edema in the right frontal lobe. Parietal empyema

Fig.3 Fig.4 Fig.5

Fig.3. Abscess after otogenic fistula: ring-shaped margin after injection of con­trast medium in the parieto-temporal lobe

Fig.4. Two abscesses with margin after enhancement in the occipital lobes

Fig.5. Tuberculous meningitis: ventricular dilatation. High density area in the left frontal and right parietal lobe

A B

A B

137

Fig.6. A. Tuberculous me­ningitis: ventricular di­latation. Hypodense area next to the right frontal horn. B. After iodine con­trast injection: tuberculous abscess within edematous area

Fig.7. A. Hypodense area, with ill limited zone of high density after iodine injection. B. Three weeks later: tuberculous abscess in the caudate nucleus. The ventricular dilatation in­creases

138

Fig.B Fig.9 Fig.lO

Fig.B. Tuberculous meningitis one year before. Right frontal tuberculoma in ede­matous area, with displacement of the ventricular system to the left

Fig.9. Encephalitis: narrowing of the ventricular system, hypodense area in the left fronto-temporal lobe

Fig.lO. Herpes simplex encephalitis one year before. Calcifications in the occipital lobe. Hypodense areas around the brain. Ventricular dilatation

Epidermoid Cyst A. Rousseau, G. Comelis, and 1. H. Vandresse

The extraordinary importance of computer tomography for the study of brain tumors is well known, but it seems even more significant for the diagnosis of congenital tumors of the dermoid cyst type. Although until lately these tumors were considered rare, we have diagnosed more cholesteatomas since possessing a CT scan than we did during the pro­ceding twenty years. Since the notion of rarity was perhaps due to the limitation of the clinical radiologic signs, it must be reconsidered.

The characteristic "crumb" or "sponge" pictures at pneumoencephalo­graphy were in fact not always displayed. In this first paper we shall only speak about some features which help the diagnosis. A more detailed study including also the tumoral features in Rathke's pouch will be soon published.

Usually the tumors are easily distinguished from the adjacent cere­bral tissue and have irregular or even scalloped outlines. They are not enhanced by contrast infusion, but contrary to ischemias their evolution is slow. Localization rarely interferes with the diagnosis, except in cases with at once supra- and subtentorial tumoral exten­sion. These tumors are of varying sizes and do not usually displace or modify the ventricles~ and if they do so, there is no correlation between the siz~ of the tumor and the degree of displacement.

All our cases exhibited EMI units from +10 to +12.

In conclusion: any +10 density area which does not modify the ventri­cles, or only slightly, is not enhanced by a contrast medium, and de­velops slowly is very likely to be an epidermoid cyst. This diagnosis will be assessed with pneumoencephalography and tomography.

140

Fig.l. (Case 607). Frontal epidermoid cyst, with den­sity +12 Hounsfield scale No. 620. Same case with contrast injection. Note that there is no enhance­ment and no ventricular deformation

141

Fig.2. (Case 6151). Infra­and supratentorial epider­moid cyst. Density +11 Hounsfield scale No. 6152. Same case with contrast injection. No enhancement

Meningiomas en Plaque B. Bittighoffer

With meningiomas en plaque a twofold diagnostic problem arises to which tomodensitometry makes a valuable contribution. This problem concerns first the determination of the bony lesion proper, - usually already visible on plain X-rays - and the assessment of its orbital or temporal extension. Moreover, tomodensitometry facilitates re­cognition of the presence of a non-ossified parenchymal part and thus the assessment of the diagnosis of the meningioma. The density values recorded after contrast infusion are very useful here since it is now well known that meningiomas rank among the tumors with the best contrast uptake.

We report three cases of meningioma en plaque verified by surgery or by their specific roentgenographic appearance.

1. Tomodensitometric Signs at the Level of the Bones of Orbital or Temporal Extension (Figs.1 and 2)

Besides the diminished volume of the orbital cavity or of the middle cerebral fossa characteristic of advanced meningioma en plaque (Fig.3A), bony signs should be sought in cases seen at an earlier stage, to pre­dict the orientation of the extension. Figure 1 shows a hyperdense bony nodule located on the posterior aspect of the lesser wing of the right sphenoid bone. Figure 2 shows numerous nodules in the area of the pterion as well as in the alar and the temporal part, extending to the middle cerebral fossa.

2. Tomodensitometric Signs at the Level of a Parenchymal or in Part of the Meningioma en Plague Undergoing Ossification

Tomodensitometry has the advantage of rendering visible the non-ossi­fied tumoral buds in meningioma en plaque. Plain skull radiographs show only the markedly ossified part and only very sophisticated angiography can in some cases recognize such buds when they are richly vascularized. Such a case is reported in Figure 3, the visualization of an intraorbital tumoral bud following intravenous infusion of contrast. The parenchy-mal part is depicted in Figure 3A, and Figure 3B points out the dif­ference between the densities before and after contrast enhancement.

The study of the density of the bud before and after infusion is sum­marized in the table below:

BEFORE INFUSION AFTER INFUSION

BASE 207 216

PERIPHERY 201 210

The profiles before infusion (Figs. 4A and 48) and after infus"ion (Figs. 4C and 4D) demonstrate the density changes at the insertion base as well as the tip of the tumoral bud.

143

These few data demonstrate the tomodensitometric contribution to the still numerous problems in meningiomas en plaque of the posterior part of the orbit, and of their transitional forms with parenchymatous meningiomas.

Fig.l. Dense bone nodule on the intracranial aspect of the lesser wing of the sphenoid bone

Fig.2. Numerous nodules on the intracranial aspect in the pterion area. The right­hand image is obtained with a high-level large window so that the isodensity points draw the bony outline

144

A

B

C

Fig.3. Meningioma en plaque involving the lesser and the greater sphenoidal wing. A. Clear visualization of a contrast-enhanced intra-orbital bud. Above polaroid, below electrostatic print-out. B. Direct comparative image (above) with isoden­sity points (below) before (left) and after (right) intravenous injection of con­trast. These images demonstrate the presence of a tumoral bud which was not visible before enhancement (~). c. Distribution of isodensities at the base of the bud (left) (~) and at the tip (right) (~) before (above) and after contrast in­fusion (below)

145

Profi le around line : 83

220

216 0 co co

c OJ

II) 212 E 0 a; )(

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201,

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,~ co 208 OJ

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0 20 1,0 60 80 100 120 B Number of columns

Fig.4. Density profile at the level of the tumoral bud (~). A. Base before en­hancement. B. Tip before enhancement. C. Base after enhancement. D. Tip after enhancement. These diagrams unambiguously demonstrate that the enhancement response is the same for the base and for the tip of the tumoral bud, but that the density level is higher at the base than at the tip. The latter finding is confirmed by a study reported by J. Cl. DOSCH

146

Prof ile around line : 72

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N euroophthalmology L. L. Mortelmans, D. Baleriaux-Waha, M. G. Dupont, L. Jeanmart, and R. Potvliege

Ever since the original description of the first CT scanner, the diagnostic value of CT scanning in neuroophtha1mo10gy has been empha­sized (1,2,10,11). The advent of the so-called second generation, or whole-body scanners, in 1974 widened the possibilities of this tech­nique by allowing a much wider choice of tomographic planes, parti­cularly useful in examining the orbits and the sellar region (8,16).

At the CT unit of the Brussels University Hospital we normally per­form CT scanning after clinical examination, plain X-ray films, and echography but before neuroradio10gic techniques involving the use of contrast media. This place in the gamut of available examination tech­niques is due to the atraumatic nature of CT scanning which allows a maximum amount of information to be obtained even in outpatients with minimal discomfort and acceptable radiation exposure.

It has been shown by several investigators that a lens dosage of 100-800 mrads is absorbed in orbital CT scanning, which is less than the dosage of a plain skull film. In conventional orbital tomography, however, it is much higher at 12 rads. In arteriography, orbital veno­graphy, and cisternography it reaches approximately 10-17 rads. Radia­tion dose, therefore, is significantly lower in CT scanning than in conventional neuroradio10gic methods (2,9,15).

Primary questions posed by the referring physicians concern the cause of the following:

- unilateral exophthalmos - bilateral exophthalmos - loss of vision - papilloedema - optic nerve atrophy - visual field defects - disorders of occu1ar motility

Our standard 8xaminat~on technique involves a series of axial scans angled at -15 to -20 from the orbitomeata1 (canthomeata1) line fol­lowed by a series of coronal or semicorona1 cuts whenever an orbital or sellar problem is suspected. Both of these series are then reviewed after intravenous contrast injection. We always use overlapping cuts to cover any gaps between adjacent slices. The use of a negatively angled scan plane is essential in order to visualize the orbital con­tents and optic pathways: in fact, all the following structures are situated in one plane: lenses, optic nerves, optic chiasm, anterior and posterior c1inoids, optic pathways and occipital cortex (14). The coronal or semicorona1 cuts have proved extremely useful in eli­minating the partial volume effect sometimes created by the orbital floor and roof and in defining the vertical extension of facial and sellar lesions. Finally, we believe that the diagnostic accuracy of CT scanning is improved by systematic density measurements, comparing the affected with the unaffected side and the unenhanced with the enhanced scan.

148

While pathologic conditions can be detected and located without great difficulty, it is not always possible to identify clearly the lesion. This is not surprising when taking into account the enormous diversity of lesions (tumorous, vascular, endocrine, inflammatory) that may be encountered, many of which present very similar CT aspects, so that a precise diagnosis on the basis of the CT scan alone is often impossible. One should always remember I. I. KRICHEFF I S maxim, "Everything can look like everything."

Generally speaking, the following signs should be looked for:

1. Changes in normal structure, e.g., bony erosion, basal cistern compression.

2. Changes in density: hypodense, e.g., cystic lesion, brain soften­ing, edema or hyperdense, e.g., some tumors (meningioma), fresh hematoma.

3. Presence of atypical calcifications of tumorous (craniopharyn­gioma, some gliomas) or vascular (calcified aneurysm) origin.

4. Enhancement of an isodense lesion not visible on the plain scan. 5. Presence of a more or less typical enhancement pattern, e.g., me­

ningioma: rounded, homogeneous abscess: annular.

We will now describe in more detail the CT appearance of pathologic conditions of the neuroophthalmologic sphere.

Intrinsic tumorous lesions (melanoma, retinoblastoma) may deform the eyeball or cause localization swelling or bulging of its wall; most of these tumors enhance after contrast injection.

Several types of lesions may involve the bony orbit. Orbital dysplasia causes an abnormal and/or asymmetrical development without changes in the bony structure. Bone erosions, on the other hand, are due to space­occupying lesions of varying origin. These may be benign (neurofibroma, eosinophilic granuloma) or malignant (skeletal metastasis). Another group of orbital mass lesions are derived from the paranasal sinuses. These lesions are often isodense or slightly hyperdense; contrast en­hancement is absent or very slight. This CT aspect is presented by several lesions: mucocele, pyocele, cylindroma, and epithelioma. It is interesting to note, however, that peripheral rim enhancement has been described in mucoceles (13). Finally, the orbital wall may be thickened due to the presence of osteoma.

CT scanning is ideally suited for showing pathologic involvement of retrobulbar soft tissues. Localized (myositis) or general (Graves ophthalmopathy) muscle swelling is well demonstrated, as is inflammatory pseudotumor. The latter condition is often bilateral and may be loca­lized or diffuse, with obliteration of normal anatomic landmarks. It arises preferentially in the orbital apex. Orbital metastases are iso­dense or slightly hyperdense and often surrounded by a large edematous zone. After contrast injection they show homogeneous or irregular an­nular enhancement. Previous knowledge of a primary tumor is, of course, very helpful in the final diagnosis. Hemangiomas represent a rather large group of orbital mass lesions (15% in one series); they are either cystic (hypodense) or solid (isodense). The optic nerves are clearly visualized on correctly angled axial and coronal scans; their morphologic appearance and symmetry should be studied and compared. Orbital meningiomas present a well-known rounded and somewhat hyperdense aspect that enhances notably after contrast injection. Optic nerve gliO­mas, on the other hand, are more irregularly shaped and of heterogeneous density.

149

The principal tumors of the sellar and parasellar regions (chiasmatic glioma, craniopharyngioma, pituitary adenoma and meningioma) fail to show any typical characteristic whether before or after contrast in­jection. However, it is useful to know that craniopharyngiomas often show different density components ranging from hypo- to hyperdense (calcium density), whereas adenomas are mostly homogeneously hyper­dense and cause sellar enlargement. Suprasellar meningiomas are simi­lar in appearance but are located more anteriorly or laterally to the sella turcica. Both adenomas and meningiomas show marked enhancement on the post-injection scan. Only 50% of the craniopharyngiomas cases enhance, whereas all meningiomas show positive enhancement.

Many different lesions in the brain stem and cerebral hemispheres may cause ophthalmologic signs and symptoms:, cerebral hemorrhage, abscess, primary tumors, secondary deposits, and cerebral infarction - all of which are well documented in classic CT texts. A typical cause of visual-field defect is occipital lobe infarction, which is visible as a localized hypodense defect of the occipital cortex both before and after contrast injection. However, it is important to realize that some infarcts may be isodense on the plain CT scan and show marked hyperdensity on the postenhancement tomogram, thus simulating neoplasm.

Conclusions

CT scanning is extremely valuable for showing pathologic conditions of the orbits and optic pathways. The presence, localization, and ex­tent of different lesions can be well demonstrated. On its own, how­ever, this technique does not yet permit definitive diagnosis: its results should always be correlated with clinical, laboratory, and plain X-ray findings. One big advantage of CT scanning lies in its atraumatic and noninvasive nature, being thus easily repeated without hazard to the patient.

The need for conventional neuroradiologic methods has decreased, but angiography and, to a lesser degree, pneumography remain necessary in certain cases.

Bibliography

AMBROSE, J.A.E., et al.: A preliminary evaluation of fine matrix computerized axial tomography (Emi scan) in the diagnosis of orbital space-occupying lesions. Brit. J. Radiol. ~ 747-751 (1974)

BERGSTROM, K.: Computer tomography of the orbits. Acta Radiol. (Suppl.) 346, 155-160 (1975)

BRISMAR, J., et al.: Unilateral endocrine exophthalmos. Diagnostic problems in association with computed tomography. Neuroradiol. ~, 21-24 (1976)

ENZMANN, D., et al.: Computed tomography in Graves ophthalmopathy. Radiology ~, 615-620 (1976)

ENZMANN, D., et al.: Computed tomography in orbital pseudotumour (Idiophathic orbital inflammation). Radiology 120, 597-601 (1976)

FAHLBUSCH, R., GROMME, T., AULICH, A., WENDE, S., STEINHOFF, H., LANKSCH, W., KAZNER, E.: Computerized Tomography, Lanksch, W., Kazner, E. (eds.).

Berlin-Heidelberg-New York: Springer 1976 pp. 114-127 GAWLER, J., et al.: Computer assisted tomography in orbital disease. Brit. J.

Ophthalmol. 58, 571-587 (1974) HAMMERSCHLAG, S.B., et al.: Computed coronal tomography. Radiology 120, 219-220

(1976) ISHERWOOD, J., et al.: Radiation dose to the eyes of the patient during neuroradio­

logical investigations. Neuroradiol. 10, 137-141 (1975)

LAMPERT, V.L., et al.: Computed tomography of the orbits. Radiology 113, 351-354 (1974)

MOMOSE, K.J., et al.: The use of computed tomography in ophthalmology. Radiology 115, 361-368 (1975)

OSTERTAG, C.B., UNs5LD, R., MUNDIGER, F.: Computerized tomography in neuro-ophthal­mology. In: Cranial Computerized Tomography. Lanksch, W, Kazner, E. (eds.). Berlin-Heidelberg-New York: Springer 1976 pp . 202-206

SALVOLINI, U., et al.: Computer assisted tomography in ninety cases of exophthalmus. J. Comput. Assist. Tomogr. Jj 81-100 (1977)

SANDERS, M.: The contribution of CAT to neuro-ophthalmology. European Seminar on Computerized Axial Tomography in Clinical Practice, London Oct. 11-15, 1976

WENDE, S., AULICH, A., LANGE, S., LANKSCH, W., SCHMITT, E.J.: Computerized tomo­graphy in diseases of the orbital region. In: Cranial Computerized Tomography. Lanksch, W., Kazner, E. (eds.). Berlin-Heidelberg-New York: Springer 1976, pp. 207-211

WOLF, B.S. et al.: Feasibility of coronal views in computed scanning of the head. Radiology, ~,217-218 (1976)

Fig.2A Fig.2B

Fig.l. Intrinsic ocular mass lesion. Note difference in size and density of right eyeball. Scan obtained after contrast injection (melanoma)

~ Unclassified dysplasia causing marked asymmetry of the orbits. Note curving of the left optic nerve

B

B

151

Fig.3. Irregular erosions of the skull in a case of Letterer-Siwe disease. No con­trast injection. Note erosion of internal left orbital wall

B

Fig.4. Metastasis to the lateral wall of left Or­bit; bone thinning and destruction soft tissue swelling with exophthal­mus

Fig.5. Cylindroma of the left maxillary antrum extending into the orbit and ethmoid. Note soft tissue mass, bone des­truction and exophtal­mos with swelling of the internal rectus

o muscle

152

Fig.6 Fig.7

Fig.S

Fig.6. Melanoma developing along the lateral wall of left orbit. Scan obtained after contrast injection

Fig.7. Right optic nerve meningioma. Note exophthalmos, retro-ocular mass and bow­ing of internal rectus muscle. This tumor showed marked enhancement after contrast injection

Fig.S. Retro-ocular metastasis

Fig.9 Fig. 10

Fig.9. Right orbital an­gioma displacing the eye­ball outward

Fig.10. Tumor of the left optic nerve. Histology not verified

A B

A B C

153

Fig.ii. Meningioma of the right orbit, sphenoidal re­gion and middle fossa before (A) and after (8) contrast injection. Note bone scle­rosis and typical rounded and homogeneous enhancement pattern

Fig.12. Craniopharyngioma. A. shows irregular mass lesion and asymmetrical sella, B.,C. show suprasellar extension. Note amputation of the anterior part of IIIrd ventricle

A B

Fig.13. Pituitary adenoma before (A) and after (8) contrast injection

A B

Fig.1SA Fig . 1SB

Fig.14. Pituitary adenoma. A. shows isodense mass de­forming the suprasellar cis­terns. Note ventricular en­largement. Marked enhance­ment after contrast injec­tion (B)

Fig . 16

Fig.1S. Para- and retrosellar hyperdense mass lesion suggesting meningioma. No histological confirmation

Fig.16. Brainstem glioma showing irregular enhancement pattern

A B

Fig.17. Postinjection scan in a patient with quadrant anopia showing hyperdense lesion of left occipital lobe: infarction with pro­fuse perfusion stimulating neoplasm. Scans without contrast were entirely normal

A

e

155

B

Fig.lS. Hyperdense cortical infarction in a patient having hemianopsia (A, B: scans taken after contrast injection). At this time the preinjection scan was normal. A follow-up study several weeks later showed typical hypodense infarct both before (e) and after contrast iniection

Arterial and Arteriovenous Malformations J. C. Dosch

The CT behavior of an intravenous contrast infusion presents several problems, especially in tumor pathology, for which the hematomeningeal membrane constitutes a more or less effective barrier to the water­soluble triiodide molecules. This is not the case in vascular patho­logy, e.g., aneurysm and AV malformations, which seems to possess its own and characteristic densitometric data.

Method

The printing device takes up the numerical data of the absorption coefficients recorded on the floppy disc. It no longer studies thin distribution on the matrix, which provides an axial tomographic sec­tion of the brain, but around a line or within a volume, thus defining profiles and histograms. This new distribution of the numerical data determines curves which give information, not only about the morpho­logic, qualitative appearance, but also about the quantitative aspect of a cerebral structure. The histogram allows us to calculate the standard deviation and the mean value and provides direct information on homogeneity of a cerebral lesion. When carried out before or after an intravenous contrast infusion (comparative histograms), it is proof of the CT dynamics of these lesions.

Material and Results

This study was carried out on an aneurysm of the Sylvian artery and on an intraorbital angioma. We have recorded identical behavior as follows.

Before Infusion

The vascular malformation exhibits a homogeneous distribution of the densities. In the case of the aneurysm, the maximal density was peri­pherally located, showing the presence of either hematomas within the walls or of microscopic calcic deposits. The mean level of density is low, almost as low as that of the pericerebral gray matter. The histo­gram seen on the left in Figures 5 and 10 presents a peak with a small standard deviation, which verifies a homogeneous distribution of the densities.

After Infusion

There is a marked shifting of the curve to the right of about 6 points densitome. Whereas the spread of the curve becomes narrow, the peak value is accentuated, showing a homogenization of the densities within the malformation.

These findings seem to be unique to arterial and arteriovenous mal­formations, since we have never observed such behavior within tumors until now.

Fig.l Fig.2

Fig.3 Fig.4

Figs.3-4. Magnification of the same aneurysm

157

Figs.1-2. Sylvian aneurysm prior to and after infusion of contrast medium

158

15

Ii,

12

III

C 10 0 0

Q.

'0 Q; .n 8 E :J Z

5

l,

2

0 190

Comporotiv histograms Exomen : 115

Levels

C'"

'" '" Cc:OV1 EEll"llJ") ;::'JQ)Q) ooce uu :'=: :':::

UiVitlUl - ~ d ·~ Cj LL ...I LL-.J

<0

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0", ~Ln

LCD'" E E'!'oll"l J:JQ)<l.I OO .~ . !:: uu - -

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QJ 01 o E

Fig.5. Histograms prior to (left) and after infusion of contrast medium (right)

Fig.6 Fig.7

Figs.6-7. Intra-orbital angioma. Prior to and after infusion of contrast medium

159

Fig.8 Fig.9

Figs.8-9. Magnification of the same angioma

Comparative histograms Examen : 0

-co 16 ~ r:-:

c:c.:c---...., EE'""~ J:lWQ.l

I/, 8e~E 1;;---I.- VI ~ 111

. - 0 ' - 0 lL-lLL-l

12 '" OJ 0>

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~ '0 ~

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et:,...-.t 6

:>E~~ -.3Q)QJ 8e~~ ~U;~v;

t. ._ 0 -- 0 LL-.JLL-.J

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0 ~ 160 200 208

Levels

Fig.10 . Histograms prior to (left) and after infusion of contrast medium (right)

ID. Trunk

Chest M. Osteaux, L. Jeanmart, J. Struyven, and R. Huvenne

Introduction: Technique

As a rule, it seems logical to limit use of CT to specific cases be­cause of the high cost. Therefore, it is advisable to concentrate on those areas which are insufficiently investigated by nontraumatic radiologic methods, e.g., the brain, the liver, the retroperitoneum, and the pancreas. The thorax, as its pulmonary area is concerned, con­stitutes a favorable field for radiology: its essentially aerial com­position brings out the normal or pathologic structures without any contrasting medium. The important contribution of simple methods such as the standard thorax and the conventional tomographies are well known.

It is therefore advisable to examine critically the specific contri­butions of CT in the pulmonary and mediastinal field. CT has the fol­lowing theoretical advantages:

1. Suppression of the superpositions without tomographic shadow, this being due to the point by point mathematic reconstruction of the picture.

2. Highly sensitive to small density variations. 3. Measures the density and deduces the composition and eventually

the nature of some components, whether normal or due to a lesion. 4. Represents the totality of the structures from the wall to the me­

diastinum, due to the variability of the picture by means of center­ing and window display.

5. New topographic approach to the area by means of axial sections. This very often constitutes a decisive factor in the topographic understanding of complex lesions and is successfully applied in planning radiotherapy of malignant lesions.

The apparatus used is the Ohio Nuclear Delta Scanner with a matrix of 256 points out of a total of 256. The cut thickness is 1.3 cm. With a scanning time of 150 s, for two cuts, it is naturally unthinkable to stop the patient's breathing, but nevertheless, there is excellent resolution. As long as the breathing is regular, the computer renders a very satisfactory average picture of the parietal, pulmonary, and mediastinal structures in general. On the other hand, the inner struc­tures of the heart are either insufficiently or not at all indivi­dualized.

CT Representation of Normal Structures

Walls (Thoracic Walls)

The skin and the subcutaneous fatty tissue are represented very well. The muscles are perfectly individualized, and the skeletal parts and the cartilaginous structures are equally quite visible.

163

Lungs

In the pulmonary area, only the vessels which are visible as far as the periphery are seen. Likewise only the main bronchi are visible and at the periphery, only the pleura. The arterial and venous hilus are represented clearly.

Mediastinum

The heart outline is globally defined but the constituting structures are not uniformly individualized, due to the rapidity and the ampli­tude of the movements. The aorta, the vena cava inferior, the main vessels of the superior mediastinum are resolved very well. The tra­chea and the main bronchi are perfectly delimited. The esophagus is not uniformly visualized (e.g., when the patient swallows air).

CT in Pulmonary Pathology

Generally speaking, CT is rather inferior to conventional methods in detecting and defining parenchymatous condensations. It is, however, quite a different situation when the lesion is in an area not favor­able for conventional radiology. We have found small-sized lesions, namely of metastasic origin, which were absolutely invisible with conventional methods in the following areas: periphery, posterior thoracic grooves, anterior cardiothoracic angle, extremity of the costodiaphragmatic sinuses (Fig.2). CT examination also proved useful in a complex situation such as the coexistence of encysted effusion and parenchymatous condensations (Fig.3). The possibility of measuring the density of a lesion sometimes permits its constituent element to be determined (Fig.4). Due to the amplitude of breathing movements and the average character of the densitometric image rendered by the apparatus, the density of small and middle-sized lesions is influenced by the adjacent aerial component.

Mediastinal Lesions

With the scanning times now used, the resolution achieved in the me­diastinum is rather poor. Therefore, compared with the theoretical possibilities of the method, the practical results are rather dis­appointing. Likewise the method proves to be uninteresting in heart pathology in most cases. An interesting exception is the research in pericardiac effusion, in which the cardiac muscle is clearly indi­vidualized from the surrounding liquid (Figs. SA, B).

In vascular pathology of the mediastinum, the aneurysms of different origins are demonstrated very clearly. The differential diagnosis of aneurysmal lumps from tumor formations is made much easier by densi­tometric study during intravenous injection of a contrast medium. The understanding of complex tumoral lesions has been substantially im­proved by CT (Fig.6), which also makes it possible to characterize unequivocally the fat-composed tumors (Fig.7).

Pleural Lesions

Here the contribution is considerable, because conventional radiology shows th~ pleura and its lesions very poorly. The intrinsic pleural contrast is in the first place very small, and besides this the pe-

1~

ripheral situation is unfavorable for ordinary radiology. With CT, how­ever, even very small effusions are disclosed. Also metastases can be observed, which are absolutely invisible otherwise (Figs.8 and 10). In particular, it may be observed in the follow-up of neoplastic diseases that the occurence in standard radiology of pleural effusions without condensation is due to small-sized pleural metastases which so far had escaped detection. The pulmonary tumors, primary as well as secondary, are very often bound to the pleura by thin opaque tracts which could represent a lymphatic extension of the disease (Fig.9). The sternopericardial ligament with its bilateral pleural reflection is particularly visualized. In case of unilateral subatelectasis, the mediastinum tips entirely over around its posterior insertions. The inclination of the sternopericardial ligament thus proves to be an early sign of subatelectasy (Fig.9).

Parietal Lesions

CT proves to be the method of choice in the study of parietal exten­sion of intrapulmonary lesions or vice versa (Fig.11). The primary tumoral formations of the wall in areas inaccessible to clinical ex­amination are perfectly shown, as well as the adenopathies of lympho­matous or metastasic origin. An original contribution of the technique is its clear representation of the neoplastic or inflammatory inva­sion of the muscles, of the subcutaneous tissue, and of the cartilages.

Mixed Topography Lesions

CT is the only investigative method able to give a direct and total representation of lesions straddling the superior or inferior thoracic limit: exothoracic extension of intrinsic lesions in the direction of the abdomen or cervical area or intrinsic extension of exothoracic lesions (Figs.12A, B). The most common examples are the endothoracic extension of tumoral formations of the inferior cervical area and the presence of subphrenic abscesses which continue pulmonary lesions.

Conclusion

In spite of an intrinsically limited area in addition to the scanning times, which decreases the possibilities of apnea, the results of CT are already interesting in a few specific cases. At the pulmonary level, the examination must be limited to the study of condensations situated in areas unfavorable for standard radiology (e.g., periphery or posterior grooves) and of complex topographic pathology. At the mediastinal level, in spite of a clearly altered resolution because of the cardiovascular movements, interesting information is achieved in tumoral and vascular pathology. Finally and above all, CT proves to be a real revolution in detecting and understanding pleural and parietal pathology.

Bibliography

CARTER, B.L., IGNATOW, S.B.: Neck and mediastinal angiography by computed tomography scan. Radiology 122, 515-516 (1977)

KREEL, L.: Computer ~ography in the evaluation of pulmonary asbestosis. Prelimin­ary experience with the EMI general purpose scanner. Acta Radiol. (Diagn.) 12, 405-412 (1976)

MUHM, J.R., BROWN, L.R., CROWE, J.K.: Detection of pulmonary nodules by computed tomography. Amer. J. Roentgenol. ~, 267-270 (1977)

165

A B

C D

E F

Fig.i. Total representation of normal chest. "Center" and "window" settings for lungs. One slice every 5,2 em. A. Diaphragmatic level, B. basis, C. venous hilum, D. main bronchi, E. arterial hilum and -carena, F. top of lungs

166

Fig.2

Fig.2. "Hidden lesion". Neoplasic consolidation (2), near the aorta (1). In A.P view and tomography, lesion masked by the dilated and displaced heart; in lateral view, vertebral column and aorta superposition

Fig.3. "Complex situation". Parenchymatous metastasis (1), pleural metastasis (2), pleural effusion (3)

A B

Fig.4. Densitometric char­acterization of a celluar massive invasion of left lung. Average density out of 596 points: 44 Houns­field units. (Note en­larged left axillary lymph nodes)

Fig.5. A. Neoplastic pericardiac effusion. Mean density of effusion: 8 Hounsfield units. B. Idem. Mean density of heart (blood and cardiac muscle, on the whole: 35 Hounsfield units

167

Fig.6. Polyadenopathy (Hodgkin's disease). Anterior adenopathy with contiguous pa­renchyma invasion (1). Right hilum adeno­pathy (2)

Fig.7. Patient suspected of having thymic tumor. Clearly characterized lymphomatosis of superior, anterior mediastinum. Mean density: 136 u.H. (fat density)

Fig.S Fig.9

Fig.S. Minimal pleural metastasic invasion (not visible on conventional tomographies). Minimal pleural effusion

Fig.9. Large bronchic adenocarcinoma. Inclination of sternopericardial ligament due to subatelectasis. Opaque tractus linking tumor to the pleura

168

Fig.ll

Fig.10. Tiny pleural and pulmonary peripheric metastasis. Capsulated pleural effusion.

Fig.ll. Wall invasion by a peripheric lung carcinoma. (Pleural effusion)

A

B

Fig.l2A. Recurrence of a cervical neurinoma operated before. Tumoral pedicle (1). Extension in the soft tissues of the neck (2)

Fig.12B. Same case. Extension of the tumor to the top of right lung

Liver M. Osteaux, J. Struyven, R. Huvenne, and L. Jeanmart

Introduction

The study of the hepatic parenchyma presents a choice field for the Total Body Scanner, since this organ is investigated only with dif­ficulty by the conventional methods of radiology. Besides the homo­geneous character of the parenchyma, the precise limits of the organ, and its lack of mobility are favorable circumstances for CT study.

The present work is based on an experience resulting from 450 hepatic investigations, the indications of which mostly concerned tumoral pa­thology.

Method

The instrument used is the Ohio Nuclear Delta Scanner. This instrument effects 13mm axial sections at the rate of 2 sections every 150 s. The densitometric picture is calculated according to a matrix of 256 points out of 256. The investigation is conducted without any angular posi­tion of the gantry by pairs of contiguous sections, so that the whole organ may be covered (the initial section is placed at the lower limit of the ribs or the liver if it is palpable). The section level is lo­cated in relation to the xiphoid process.

While the patient fasts, the investigation is preceded by an intra­muscular injection of 3 mg of glucagon. This systematic administration of an inhibitor of intestinal peristaltism has proved to be, in our experience, of considerable importance towards improving the pictures by reducing the artifacts caused by intestinal gases in motion.

During the first eight months of our study, a first series of sections was realized without contrast, a second one after intravenous injec­tion of contrast medium. The extra amount of information gained by this double investigation seemed extremely small to us. So nowadays in order to limit the irradiation dosage and in order to save time for the department we make only one series of sections after the intra­venous injection of 100 cc of 76% urographin. The weight and size of the patient are taken into account for correlation with the liver size.

CT Picture of the Liver

The sequence of the effected sections gives a total spatial picture of the organ with excellent defining of the relations to the adjacent organs (Figs.1A-F). The general morphology of the liver is extremely variable according to the morphotype. On the other hand, it is possible, by intergrating the various axial cuts, to calculate, either by means of a special program or by means of a programmed calculating machine, the total volume w~th a remarkable accuracy and to correlate it with the body surface.

170

The different structures constantly present are the gallbladder, the main portal trunks, the main biliary ducts, and the interlobar scissurae. The normal parenchyma seems to be of homogeneous structure and is of high density: 60 - 70 Hounsfield units on the average. Af­ter the intravenous injection of 76% urographin at the rate of a 1.5 ml/kg body wt. dosage the density doubles practically within the fol­lowing two minutes and falls progressively to about 80 after 12 min (Fig.2).

KORMANO and DEAN have shown the part played in the rise of density by the incorporation of the contrasting medium into the extravascular compartment. This phenomenon however is important only in the period immediately following the injection.

Because in liver the sinusoidal vascular space represents a consider­able proportion of the organ volume, the simple radiologic coloring of the vascular space is sufficient to increase perceptibly the total density. Our microangiographic studies show that the circumscribed liver lesions whatever their etiology are less rich in microvessels than the contiguous parenchyma. That is why the injection of a con­trast medium increases the densitometric lesional differentiation from the environment.

Inflammatory Lesions

Hepatic Abscess

The examination shows a heterogeneous plaque of lesser density (be­tween water and tissular density). The injection of a contrast medium causes the appearance of a more opaque zone at the periphery but af­fects the central density very little. These facts added to the clin­ical information make the etiologic diagnosis possible. A particular case is the amibian abscess which tends to evolve toward a simple cys­tic image.

Subphrenic Abscess (Fig.3)

This pathology produces a rather homogeneous zone of lower density under the diaphragm or at the limit of the upper liver. The limits in relation to the normal parenchyma are convex and fairly sharp, so that these characteristics are generally sufficient to make the diag­nosis.

Hepatitis

The diffuse parenchymatous alteration process is invisible in CT, at least in the present state of technology.

Other Nontumoral Lesions

Cirrhosis (Fig.4)

In its present form, the examination is uninteresting for investigat­ing the cirrhotic liver, because as a rule density differences in re­lation to the normal liver are of little significance for identifying the disease. However, CT will prove a possible hepatosplenomegaly or a lessening of the organ size. The heterogeneous densitometric charac-

171

ter of some cirrhotic livers ar~s~ng from the alternation of necrosis and of regenerating centers is also likely to disturb the diagnosis of an additional hepatoma.

Hepatic Steatosis

The global and homogeneous lessening of the density as well as the re­duction of the densitometric intensification after IV injection of contrast medium strongly suggests this diagnosis.

Trauma (Fig. SA, B)

CT is also useful for identifying a possible hepatic trauma. (Demon­stration of fractures and hematoma) .

Ascites (Fig.6)

The existence of an ascites at the liver periphery is likewise quite visible.

Biliary Tract Dilatation (Figs.7A-C)

The extra hepatic block of the biliary ducts is shown by a dilatation of the intrahepatic tract, seen thanks to radially grouped lacunar structures in the parahilar region. Densitometry and picture arrange­ment make a differential diagnosis from metastasic infiltration pos­sible.

Cysts and Tumors

In our experiments, the method proved of great value in the diagnosis of circumscribed tumoral lesions. The following are discussed: cysts, primitive tumors, hepatic invasion of adjacent tumors, metastasic le­sions. An understanding of the CT visualization of these lesions ben­efits largely from thorough anatomicopathologic correlation and from a microangiographic comparison.

Cystic Lesions (Figs.8A-D, 10A,B)

CT easily shows the cystic formations in the liver under the different but common circumstances - biliary cysts, hepatorenal polycystosis, hydatid cysts - and presents the densitometric proof of their liquid nature. The simple cystic formations have the aspect of round sur­faces of a small density (10 Hounsfield units on the average) dis­tinctly delimited from the adjacent parenchyma. The density of the cysts is generally not affected by intravenous injection of contrast medium. However, in the case of a hydatid cyst, contrast medium shows an opaque edge at the limit of the cyst (this is to be compared with the arteriographic appearance of these lesions, their hypervascular edge). Some very small cysts (about 1.5 cm in diameter) situated in the center of the parenchyma had escaped detection by all other meth­ods of investigation but not by this method.

172

Primitive Tumors of the Liver

Besides the few cases of infrequent malignant tumors we have met and which were easily diagnosed as tumoral formations, even if the cause was unknown, two cases seem to deserve a special description and discus­sion owing to their frequency and their particular visualization: the hepatocarcinoma and the cavernous angioma.

Hepatocarcinoma (Figs.11A-D) mostly has the form, from an anatomico­pathologic pOlnt of view, of a located mass or a diffuse infiltration starting from differentiated cell cords rather s:Lmilar to the normal hepatocyst. An important peculiarity of this tumor is the absence or the lack of spontaneous necrosis even in large formations. Since the microcirculation of the tumor is relatively rich, the tumor is conse­quently seen in CT as a relatively homogeneous mass or infiltration with a small densitometric differentiation from the normal hepatic parenchyma (from 10 - 20 units smaller density) with indistinct limits. The tumoral mass absorbs the contrast medium, and swelling of the hep­atic limit is noticed when the tumor reaches it. All the hepatocar­cinomas we have observed were large sized and were easily character­ized, so, difficulties may occur in the diagnosis of small and medium sized tumors. The problem of differential diagnosis of hepatoma from regenerating nodule also seems difficult in cirrhosis (the more so as it is to be found in a modified parenchymatous environment which is consequently densitometrically disturbed) .

Cavernous angioma (Figs.12A-C) is a tumor consisting of a hypervascular cortex with angiomatous and aneurysmal structures. In the tumor center are found old hematomas and cystic degenerative plaques separated by only slightly vascularized walls and framework. CT without any contrast medium clearly differentiates the tumor from the normal parenchyma. The tumoral density of the central region, which is of a more important volume, is small, averaging about 20 Hounsfield units, between cystic and tissue density, when the densitometric probe ("Joy Stick") is wide open with an important densitometric standard deviation thus showing the lack of homogeneity of the structure. If the densitometric probe is smaller and slightly displaced in the tumoral area it shows impor­tant variations of density.

Metastasis (Figs.13A,B,C - 15)

Metastasis has been the most usual indication in our experience, with 30 cases diagnosed as such and until now only four false negative and one false positive. From an anatomicopathologic point of view the liver metastasis looks like a formation with a very different cellularity and therefore different density from the hepatic parenchyma. Moreover, the metastases are hypovascular compared with the liver, as far as their microcirculation is concerned in any case (even the hypervascular le­sions in angiography). The formation shows distinct limits compared with the healthy parenchyma. Consequently all conditions are fulfilled for a good CT individualization of the metastases (+ 30 Hounsfield less than the normal parenchyma which increases to a difference of 70 Houns­field after injection of contrast medium. The center of the metastases, when necrotic, exhibits a cystic density, which in our experiment, was the cause of a mistake in a diagnosis. The protrusion of the metastasis onto the liver edge is rather rare.

It is interesting to pose the question of the minimal size of the dis­covered lesions. A scientifically valuable answer is rarely given in a study on the value of different methods. Indeed, the visualization

173

of a few pictures with X diameter does not imply the constancy of these observations. For the moment, we are making a study controlled by anatomicopathology, the results of which are not statistically val­uable yet. Nevertheless, the material for a partial answer is given in a histogram concerning the size of 59 measured metastases (Fig.16). It is to be noticed that 21 metastases of less than 2 em have been dis­covered and 22 of 3 em. The larger metastases which are more seldom seen are obviously easily detected. Therefore, if it is possible, in certain favorable cases to characterize metastases with 1 - 1,5 cm diameter, a diameter of 2 - 3 cm and larger seems to be a reasonable appreciation concerning metastases resolved with good constancy.

Extrinsic Invasion (Figs. 17A-C)

Besides metastasic invasion, the liver can be extrinsically invaded by contiguous tumors, a particularly interesting case of which is dem­onstrated, concerning a large malignant tumor of the right kidney superior pole. These tumors are said to grow slowly, and because of the proximity of the kidney superior pole and the liver, the pressure of the tumor was sufficient to effect a spectacular displacement with hypotrophy of the right lobe and compensatory hypertrophy of the left one.

Conclusion

In the present state of technology, CT seems to be an interesting meth­od for the study of circumbscribed liver lesions: abscesses, sub­phrenic abscesses, cysts, primitive, and secondary tumors, the densi­tometric differentiation of which is distinctly improved by intravenous injection of contrast medium. This method also makes possible an in­teresting definition of the global organ morphology and clarifies its relation to neighboring structures. The method's limitations in the matter of definition seem to be essentially linked with scanning times, since movements of various origin are responsible for blurring and ar­tifacts. Therefore, technological progress will certainly improve the already interesting results in this field.

Bibliography

ALFIDI, R.J., HAAGA, J.R., HAVRILIA, T., PEPE, R.G., COOK, S.A.: Computed tomo­graphy of the liver. Amer. J. Roentgenol. 127, 696-704 (1976)

KORMANO, M., DEAN, P.B.: Extravascular contrast material: the major component of contrast enhancement. Radiology 121, 379-382 (1976)

IAMARQUE, J.L., BRUEL, J.M., DONDELINGER, R., et al.: La tomometrie du corps entier. Premiers resultats dans l'exploration du foie et perspectives d'avenir. Medecine et Chirurgie digestives 2.1 449-454 (1976)

SHEEDY, P.F., STEPHENS, D.H., HATTERY, R.R., MUHM, J.R., HARTMANN, G.W.: Computed tomography of the body: initial clinical trial with the EMI prototype. Am.J. Roentgenol. 111, 23-51 (1976)

STEPHENS, D.H., HATTERY, R.R., SHEEDY, P.F.: Computed tomography of the abdomen. Radiology 119, 331-335 (1976)

A

e

E

1M

Fig. lA-F. Total representation of the liver from lower right lobe (A,B) with gall­bladder (arrow) liver hilum level (e,D) and diaphragmatic area with diaphragmatic sinus (E,F). Note the homogeneity of liver density

B

D

F

200

150

100

50 25 t

o

175

PAII[II(ImVITOUS O[NSIIY OF lI1'l'R AIITI WIIIH Fig.2. See text

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Fig.3. Subphrenic abscess: homogeneous, regular image of lower density at the peri­phery. Mean density measured out of 68 matricial points: 15 Hounsfield units

Fig.4. Hepatic atrophy, due to cirr­hosis (previous splenectomy)

176

B

Fig.SA-B. Traumatic liver hematoma. Large homogeneous area with a density approach­ing blood dens i ty: 28 Hounsfield. Note air in the peritoneum (arrow ) . B. Hema­toma protusion under the liver

Fig.6. Ascites. Regular, homogeneous, water=density image surrounding the liver

177

Fig . 7A-C. Biliary tract dilatation (extra hepatic block). A. "Tree branch" image due to a dilated biliary confluent (arrows). Note posterior cyst of right kidney. B. Note the decreasing diameter of lacunar images from the h ilum to the periphery. C) Densitometric differen­tial diagnosiS with metastasis. Mean densi ty: 13 H. u. (bile density)

A

C

178

Fig.SA-D. Biliary cyst. A. Homogeneous, low-density image with sharp border. With closed "window" and "center" set at 20, note the homogeneity of the liquid mass (B). C. Lower left lobe entirely occupied by the cyst. Thin layer of parenchyma at the lesion border, opacified with contrast medium (arrows). D. Protrusion of the cyst under the liver. Typically cystic mean density: 13 Hounsfield units. Note the cyst does not take contrast medium

A B

Fig.9A-B. "Pressure" protusion of a renal cyst in lower right lobe. B) Clearly of kidney origin (posterior upper pole) •

A B

179

Fig. lOA-B. Hydatic cyst (without contrast). A. Homogeneous lesion of lower density (arrows). Atrophy of the right lobe. Compensating hypertrophy of the left lobe. B. Same case, with contrast. Subdiaphragmatic level. Bilocular cyst with dense bor­der (arrows)

A

180

Fig. 11A-D. Hepatocarcinoma developed upon cirrhotic liver (note splenomegaly). A. Enlargement of right lobe with "patchy" heterogeneous, lower density image. With "Center" set at 60 and closed window, note heterogeneity of tumoral density (B). C. Densitometric study of the tumor (with contrast). D. Rather small differential density with normal parenchyma of the right lobe (difference of approximately 20 Hounsfield units)

B

Fig. 12A-C. Cavernous angioma. A. En­larged left lobe with irregularly out­lined heterogeneous, low density image (1). Dense border (2). Compensating hypertrophy of the left lobe (3) . B. Densitometric study (with contrast). High density of the hypervascular tumoral periphery (arrow). C. Near density of water (Mean: 8). Cystic degeneration of central part of the tumor

B

C

182

Fig . 13A-C. A. Large metas­tasis (gene ralized melano­sarcoma). Densitometric study . Mean density of nor­mal parenchyma out of 68 points: 64 Bounsfield units . B. Mean density of the metas­tasis: 43 Bounsfield units (tumoral cellular density). C. Mean density of the tumor­al central area : 16 Bouns­field units . (Central necro­sis of metastasis)

A

B

C

Fig.iS

Fig.14. Metastasic invasion from gastric carcinoma. Ill-defined, patchy image of lower density (arrows)

Fig.iS. Protusion of 3 em-diameter metastasis at the liver edge (arrows)

H£PATIC IlEllSlASIS. t.l. SIUDY IN 1Il CASES, 8 DIFFUSE IIIVASIOII

59 LESIONS IlASUREO IN 12 CASES

21 22

6 I 5 I 5 I 1-2 2-3 3-~ \-1 1'1+

Fig.16. See text

DIAllElER (Ull

183

184

A

C

Fig.17A. Large tumor of right kidney (upper pole)

Fig.17B. Contiguous invasion of right lobe (arrows)

B

Fig.17C. Atrophy of the right lobe due to long-term pressure of the tumor. Compensating hypertrophy of the left lobe

Liver and Pancreas J. L. Lamarque, J. M. Bruel, R. Dondelinger, and B. Vendrell

Material and Method

Equipment

The whole-body ACTA SCANNER in use since October, 1976, has the fol­lowing characteristics: A first generation scanner sweeps across in two phases every 330 s to procedure two 5 mm-wide adjacent tomographic sections which are reproduced on a 320 by 320 point matrix.

Examination Method

We have performed over 250 abdominal explorations, particularly for radioclinical liver problems. Prior to the examination, we locate the vertebral levels which appear on the abdominal wall of the patient, using television control and an orthogonal beam. A previous X-ray of the front of the abdomen enables us further to verify the absence of contrasting products in the alimentary canal, to locate precisely the surgical clips, and to perceive the development and the location of the full parenchyma of the abdomen in order to define the area to be ex­plored in CT. The tomographic sections obtained are 1.5 cm apart. An average of 8 - 15 sections is necessary depending on the liver morpho­logy. An injection of 4 ml isopropamide intramuscularly at the begin­ning of the examination reduces the artifacts induced by peristalsis. The densitometric resolving power is around 0.5% on present scanners. All studies agree about and underline the often slight differences in density existing between the various normal abdominal bowels and even between a healthy and a tumorous parenchyma. In these cases it is necessary to use artificial contrast medium.

Contrast Mediums

Water-Soluble Medium. Our experience has shown that density differences between sound tissue and intraparenchymatous lesions at the liver and pancreas levels are not significantly modified by injecting water-sol­uble opaque-making substances even at a high dosage. However, a precise comparison of the absorption levels of healthy and pathologic zones before and after the injection of water-soluble substances supplies interesting information on the vascularization of the lesion.

Biliary Opaque-Making Substances. The per os administration of vesic­ular opaque-making sUbstances at a low dosage (1 - 2 g) the day before enables the location of the gallbladder during the tomographic exami­nation. Although the slow intravenous infusion of opaque-making sub­stances of the biliary tracts does not seem to be interesting for the study of the liver parenchyma, it does enable us to verify the presence of a higher biliary junction and of swollen intrahepatic biliary tracts.

186

Iodolipids. The arterial (A.G. 52 315) or venous (A.G. 6099) injection of emulsified iodinated lipids at a very low dosage seems promising for the diagnosis of small lacunary pictures as we have experimentally shown in the pig.

Results

Liver and Pancreas Radiographic Anatomy

Comparison of the scan sections performed on a dead body and the ana­tomic sections performed on the same dead body at the same levels en­abled us to establish a precise radiographic anatomy that we can see also in vivo. The overall full parenchyma are clearly visualized. Their good resolution depends on the perivisceral grounds, particular­lyon the retropancreatic and perirenal layer of fat.

Hepatic Radiographic Anatomy. The seriated sections clearly define the topography and the morphology of the organ. The outlines are clear and regular. The relations with the other full parenchyma (kidneys, pan­creas) and hollow organs (stomach, right and transverse colon, duo­denum) are simultaneously delineated. The lobe division is very often easily recognized, whereas the segmental systematization presupposes the effort of a three dimensional construction of the transaxial sec­tions. The gallbladder or the lower vena cava are responsible for hypo­dense pictures of intrahepatic projection, with characteristic shape and topography. The liver hilum appears as V-shaped hypodense pictures which penetrate more or less deeply into the liver parenchyma. Under normal conditions, it is impossible to differentiate the various in­trahepatic biliary or vascular structures. From the densitometric point of view the hepatic dome is a silent zone, induced by the sudden tran­sition between the rear pleuropulmonary splints and the segments of the right lobe convexity.

Pancreas Radiographic Anatomy. The most important radiographic-anatomic mark is represented by the retropancreatic fat layers. The cross sec­tion of the superior mesenteric artery is regularly identified in the retropancreatic space. At the front, the stomach is in close contact with the pancreas, which makes the accurate definition of the corporal part difficult. The ingestion of a 1 - 10% water-soluble iodinated so­lution, possibly combined with a right lateral decubitus position, is an easy way of defining the pancreas in order to clear the top of the liver hilum area.

The more or less important obliquity of the pancreas on the front view appears differently in CT. The horizontal pancreas is entirely includ­ed in one section, whereas the oblique pancreas requires several con­tiguous sections showing successively from the bottom upward: the ce­phalic part is included in the liver hilum. The prerachidian corporal part shows a constant obtuse angle opening on the rachis. The more or less long caudal part has two constant marks: the left kidney and the spleen. In some cases the splenic vein is clearly visible, following behind the pancreatic tail.

ALFIDI and co-workers have shown that the isolated densitometric ana­lysis is of no value at the pancreas level. Though the uniform hypo­densities of the pseudo cysts or of the pancreatic calcifications al­though slight, are verified without any difficulty, CT cannot show small pancreatic tumors, which do not distort the outlines of the gland, on the one hand because of an unsufficient precision of the average ab-

187

sorption levels of each point, and on the other hand, for histologic reasons when concerning more or less hypervascularized lesions which do not induce remarkable densitometric difference.

Comparative Densitometries. The quantitative analysis of the picture enables us to establish the levels of average density volume of all the represented organs. The rachis and costal sections of the skeleton are the most dense, the perivisceral fat, the least dense. Among the full organs, the hepatic and splenic parenchyma, which are the most dense, have practically identical absorption coefficients. The adrenal glands and the pancreas present the lowest densities of the full ab­dominal parenchyma. Between these two extremes we find the more or less intricate absorption levels of the kidneys, muscles, big vessels and alimentary canal.

Application to Liver Pathology

Diffuse Liver Conditions

When they do not induce any morphologic change, these conditions re­main latent in CT. We have not noticed a significant difference in density between a normal liver, a cirrhotic liver, a cholestatic liver without any swelling of the intrahepatic biliary tracts, or a cardiac liver. However, two types of diffuse condition benefit by CT:

1. Hepatic steatosis in its advanced phase appears as a very marked overall hypodensity of the liver, in which in exceptional cases the portal structures come out.

2. Hemachromatosis induces a uniform, completely pathognomonic hyper­density of the liver and the spleen.

With the quantification of pictures it is possible thus to trace the evolution of the disease as rigorously as by a biologic method.

Tumorous Liver

The morphologic resolution depends on the differences in density e~ist­ing between two contiguous zones. It is therefore interesting to in­crease the densitometric gradient between the sound parenchyma and the tumorous lesion by electively making the nontumorous parenchyma opaque. With iodolipids we have tried to determine experimentally in the pig the smallest visible intrahepatic hiatus in tomometry.

Experimental Methodology. In the anesthetized pig, a first scan of re­ference is done. After a laparotomy has been performed, wooden sticks of 4,3 and 2 mm in diameter are introduced into the liver along its axial direction. A second scan is done which shows the wooden sticks present in the liver as hardly visible hiatuses. Only 1/10 of the dosage of iodolipids used in conventional hepatography (A.G. 52 315) is then injected into an epiploic vein. A further scan clearly shows intrahepatic hiatuses of 2 mm in diameter within a dense and homogeneous liver.

Clinical Application. CT enables us to visualize the overall modifi­cations of the organ: hepatomegaly associated or nonassociated with a splenomegaly, presence of a slight ascitic plate, irregular outlines of the liver. Inside the parenchyma, tumors generally appear as hypo­densities with special characteristics according to their etiology.

188

Nonmalignant Tumorous Lesions

Cystic, parasitic lesions appear as regular, sometimes large, hiatuses with absorption levels deviating from the sound parenchyma. However, older cysts with a mastic content also present absorption levels too close to a normal hepatic parenchyma to allow a precise diagnosis with­out cystic calcifications. Solitary cysts or a hepatorenal polycystic disease give regular, multiple, and hypodense pictures. A summary of the hepatic and renal extension is done simultaneously.

Nonmalignant Lesions. Very often they are hypervascularized tumors of the hamartoma series which, because of a vascularization similar to the one of some malignant tumors, sets the problems of a difficult diagnosis. When calcifications are present, a precise topographical diagnosis is easily done.

Malignant Tumorous Lesions

Primitive Tumors. Hepatocarcinoma distort very quickly and very noticeably the hepatic outlines. The tumorous picture is formed by "thick grain", with more or less spread-out and heterogeneous areas. The injection of water-sol­uble contrast medium makes the sound parenchyma more homogeneous whereas absorption levels of the tumor are hardly increased.

Secondary Tumors. There is no privileged area in proving hepatic metastasis. Both right and left lobes are explored in the same simple manner. The pictures of hepatic metastasis are almost always regular hiatuses, varying in size, with absorption levels lower than or equal to the hepatic par­enchyma. It seems that the vascularization determines the density level. In fact, hypovascularized, essentially colorectal metastasis always produce hypodense pictures that can be identified spontaneously. Hypervascularized or "edged" metastasis of a small volUllie is difficult to diagnose when they are smaller than 2 cm. Either the intra-arterial administration of iodolipids in man at the end of the coeliomesenteric exploration or intravenous administration during the ambulatory examina­tion at 1/10 of the usual dosage, is indicated in the diagnosis of small metastases, especially in a presurgery summary. Generally, metas­tasis of approximately 1 cm can be diagnosed.

Infectious Lesions

An abscess in a parasitic or bacterial liver induces a hiatus with ir­regular outlines and with a heterogeneous content, which, however, is always less dense than a healthy liver. The difference in absorption levels in healthy liver abscess is smaller than the densitometric dif­ference of healthy liver cyst.

Dilatations of Intrahepatic Biliary Tracts

The diagnosis of dilatation of intrahepatic biliary tracts can be given spontaneously without introducing biliary opaque-making substances, even with a moderate dilatation. The increase in width of the biliary tracts appears as a bigger V-shape picture, corresponding to the larger and higher biliary junction and to hypodense radiographic pictures starting in the hilum. The transverse sections of dilated biliary ca­nals on the right have produced lacunary or round pictures.

189

Liver Trauma

In hepatic trauma, CT can rapidly sum up hepatic attrition and dilacer­ation zones.

Anomalies in the Liver Development, either congenital or acquired after a lobectomy, benefit by a precise CT summary, capable of correcting the diagnosis of a tumorous hepatomegaly. Examinations done successively after a hepatic lobectomy also enable the follow-up of the hepatic re­generation in time, and in the future, the evaluation of the hepatic volume.

Conclusion

Over 250 tomometric liver explorations were performed. Anatomic and CT comparisons on nonfrozen corpses have enabled us to establish a detail­ed radio-anatomy constantly renewed in vivo. The study of the respective histograms reveals densities which are characteristic of the different abdominal parenchyma. Biliary opaque-making substances present only a very limited interest in hepatic CT. During a precise CT analysis of the data, water-soluble opaque-making substances enable indirect in­formation on the vascularization of a healthy parenchyma and a tu­morous lesion. Low dosage iodolipids seem to us to be clearly indi­cated in the diagnosis of small, tumorous lesions, as was proven by the experiments done in the pig. CT is of little interest however, in the diagnosis of diffuse hepatic conditions without any extra hepatic mor­phologic incidence except steatosis in its advanced phase and the min­eral overloads such as hemochromatosis. All nonmalignant or malignant tumorous lesions are alleviated by CT which can establish a precise to­pographic diagnosis of a liquid or solid type. Hepatic trauma, dila­tations of intrahepatic biliary tracts, or problems set by pseudo tu­morous hepatomegalies are solved by CT without adding any contrast me­diums.

Bibliography

ALFIDI, R.J., HAAGA, J.R., HAVRILLA, T., PEPE, R.G., COOK, S.A.: Computed tomo­graphy of the liver. Amer. J. Roentgenol. 127, 696-704 (1975)

ALFIDI, R.J., HAAGA, J.R., MEANEY, T.F.: Computed tomography of the thorax and ab­domen; a preliminary report. Radiology 117, 257-264 (1975)

KREEL, L.: La tomographie informatisee a l'aide de l'EMI-SCANNER pour le corps entier. Medicine et Hygiene 1202, 1076-1083 (1976)

KREEL, L.: The EMI whole body scanner: an interim clinical evolution of the proto­type. Brit. J. of clinical equipment~, (1976)

LAMARQUE, J.L., BRUEL, J.M., DONDELINGER, R., et al.: La tomometrie du corps entier. Premiers resultats dans l'exploration du foie. Nouvelle Presse Medicale ~, 1366-1369 (1976)

LAMARQUE, J.L., BRUEL, J.M., DONDELINGER, R., et al.: La tomometrie du corps entier. Premiers resultats dans l'exploration du foie et perspectives d'avenir. Medecine et Chirurgie digestives ~ 449-454 (1976)

LEDLEY, R.S., WILSON, J.B., GOLAB, T., ROTOLOSS, : The ACTA-SCANNER: the whole body computerized transaxial tomograph. Comput. biol. Med. ~ 145-155 (1974)

190

A

B

Fig. lA-B. Computed tomo­graphic and comparative anatomic stuy on the same level of the ab­domen

Fig.2. Normal appearance of the principal paren­chyma of the abdomen. Note the presence of a calcified gallstone

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Fig.3. Normal scan of the abdomen

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192

Fig.5. Normal appearance of the organs of the up­per abdomen

Fig.G. Normal horizontal pancreas: Note the presence of the superior mesenter­ic artery behind the pan­creas

193

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Fig.7A-e. (A) Normal hori­zontal 11 ver, (B) parenchy­matous phase of an arterio­gram of the same liver, (e) spatial reconstruction of the liver volume from the eT section

194

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195

Fig.ll. Huge hepatocarci­noma developed from the right lobe to the liver

Fig.12. Small metastases of the right lobe after he­atography with an iodinat­ed emulsion. Note the intra­hepatic projection of the inferial vena cava

Fig.13. Comparative absorption values of metastases and normal liver

196

Fig.14. Diffuse metas­tases of the liver best seen after hepatography with an iodinated emul­sion

Pancreatic Disease Y. Coenen, G. Marchal, E. Ponette, A. L. Baert, and 1. Pringot

Technique

All examinations of the pancreas are made after injection of a strong hypotonicum (1 mg glucagon IV) to avoid the interference of artifacts emanating from gastrointestinal peristalsis. It is the motion of air rather than its presence that creates undesirable artifacts. Respi­ratory motion also results in artifacts that seriously degrade image quality. This is partly offset by the use of abdominal compression.

In a routine examination two series of images are made. A first series is carried out in the supine position, a second one in the right de­cubitus position or, even better, in left oblique position. Before the examination, 200 cc gastrografine solution diluted to 5% are adminis­tered. The lateral decubitus position and the left oblique anterior position are particularly effective for delineating precisely the an­terior side of the pancreas as well as the pancreatic head, since it contrasts with the opacified stomachal and duodenal outline (Fig.1 and Fig.2).

Opacification of the biliary tract by a cholangiographic medium in­jected intravenously can also be useful by allowing the examination of the relation between the terminal part of the biliary duct and the duodenum (Fig.3). However, since the IV administration of a hydrosol­uble iodine contrast medium to increase the contrast of the pancre­atic gland itself gives insufficient results, the procedure has been abandoned. Thus, contrast mediums play only an indirect role in ex­ploring the morphology and pathology of the pancreatic gland. In con­trast, the role played by position is more direct. Examination in a single position, either the supine position or the right lateral de­cubitus, has assured a good visualization of the pancreas in 49% and 59%, respectively of our cases. In our experience (more than 450 cases suspected of pancreatic disease) a combination of both positions in­creases the success rate to 85%.

Normal Axial Anatomy

The pancreatic gland is an elongate, parenchymatous retroperitoneal organ, consisting of three distinguishable parts: the head, the body, and the tail.

As for the head, the principal anatomicotopographic relations are:

1. To the back, the great vessels: the inferior caval vein and the aorta. The origin of the superior mesenteric artery on the aorta is a useful landmark for locating the upper border of the pancreas.

2. To the front, the gastric antrum. 3. The duodenum, which is wrapped around the head of the pancreas and

delineates its superior, lateral, and inferior borders.

198

The pancreatic body, is elongate and extends to the left, usually slightly upward~otopic explorations have proved the pancreatic shape to be very variable and either ascending or descending as well. Its topographic relations are:

1. To the back: the upper pole of the left kidney and the left adrenal gland.

2. To the front: the horizontal part of the stomach. At the upper mar­gin of the pancreas lie the splenic vessels.

The length of the pancreatic tail is also very variable, perhaps even reaching the splenic hilus. To the front, its topographic relations are the angle of Treitz and first jejunal loops.

Radiographic Anatomy in CT

Due to its slanting position, ascending or descending, it is difficult to visualize the pancreatic gland entirely in a single section (Fig.3). To localize the pancreas it is first necessary to find the head, the principal landmark of which is the superior mesenteric artery, its ori­gin corresponding to the superior margin of the pancreatic head (Fig.3).

The relations between the pancreas and the duodenum are best explored in the oblique left anterior position after opacification with gastro­grafine. Generally the body and the tail are found on higher sections, so that often three or more sections are needed to visualize the whole pancreas (Fig.1 and Fig.2). The localization of different organs con­tiguous to the pancreas, such as the stomach, the duodenum, and the loops of the small intestine, can result in false pathologic images, owing to addition of their normal image to the pancreatic shadow. How­ever, by combining the two described techniques (supine position and right lateral decubitus with opacification of the stomach and the duo­denum) it is easy to avoid these "trap" images (Fig.4 and Fig.5).

Medical Analysis: Criteria

In evaluating the pancreatic scans, the following criteria must be con­sidered relevant:

1. The global morphology and topography of the pancreas. 2. The anteroposterior diameters of the different parts of the organ.

In his statistical studies, Haaga compared the anterioposterior diam­eters of head, body, and tail with the width of the transverse diam­eter of the adjacent vertebral body. According to these studies, the head should measure at least a half of this diameter and at most b~ equal to it. Anteroposterior diameters between one-third and two-thirds of the widest transverse diameter are considered normal for the body and the tail. However, it must be noted that these values are averages and that somewhat larger measurements are considered normal in young pa­tients. In older patients, on the contrary, an atrophic pancreas is not necessarily pathologic (Figs.6-8).

3. Regularity of the pancreatic contours.

The interpretation of this feature is very problematic and should be related to the total quality of the scan images. Obliterations of the contours are imputed to localized edematous tumefactions or fibrotic retractions as seen in cases of chronic pancreatitis (Fig.9).

199

4. Obliteration of the peripancreatic fat planes ("silhouette sign").

Since the thickness of the fat planes is related to the patient's obesity, this criterion should be handled with care. Whereas the loss of a major fat plane in an obese patient is a strong argument in fa­vor of infiltrating pathology, this very same sign of nonvisualization of peripancreatic fat planes should be interpreted much more carefully in a thin person. The presence of fat planes eliminates with near cer­tainty an infiltrating pathology. Nonvisualization of a fat plane on the other hand permits no conclusion, except when there are also other signs of infiltration, such as alterations in and enlargement of ad­jacent organs (Fig.10).

5. Homogeneity of the pancreatic parenchyma (Fig.9 and Figs.14-16).

Since the homogeneity of the pancreas is greatly influenced by arti­facts, its interpretation is only reliable when clear density dif­ferences are observed, such as opaque areas due, for instance, to calcifications of chronic pancreatitis or hypodense areas due to pseudocystic formations.

Of the five criteria given, the first two are the most reliable, since they can be studied even on images slightly disturbed by artifacts. The interpretation of the other three criteria requires examinations performed under optimal CT conditions, i.e., a sufficient thickness of the fat planes and a total abscence of artifacts (Fig.11).

Pancreatic Pathology

Acute Pancreatitis

Whereas in cases of acute pancreatitis, a normal CT image is often ob­tained, in other instances the pancreas is augmented in volume in a diffuse or localized manner (Fig.12). Besides the enlargement, the pancreatic contour can be irregular and the fat planes obliterated by inflammatory infiltrations (Fig.13). These signs are particularly fre­quent in cases of necrosis.

Chronic Pancreatitis

Macroscopically, a chronic pancreatitis can present itself under dif­ferent forms. Depending on the degree of fibrosis or edema, which in addition may be complicated by pseudocystic formation, the gland can show either an atrophied aspect (Fig.9) or, on the contrary, a tume­fied and rather pseudo tumoral appearance (Fig.14).

In cases of calcified pancreatitis the stones existing in the main pancreatic duct can easily be visualized by means of a CT examination, unless artifacts disturb the image. Cystic dilatations of the excre­tory ducts, on the contrary, are generally extremely difficult to re­veal (Fig.15).

In cases of chronic pancreatitis, the homogeneity of the images can also be altered by the formation of pseudocysts, a complication that is very frequent in acute phases (Fig.16). In contrast to well-formed pseudocysts, which pose no problems of differential diagnosis, pseudo­cysts which are still in their formation stage can cause problems of differential diagnosis from tumors, because their contents are rather dense due to the necrotic rests and because they still infiltrate

200

(Fig.16). Thus, infiltration of the peripancreatic fat planes, though mostly a sign of tumoral involvment, can also occur in cases of chronic pancreatitis.

Pseudocysts

In the course of acute pancreatitis or in acute phases of chronic pancreatitis, pseudocysts can start to develop. At first these pseudo­cysts are only vaguely delimited and are characterized by high den­sity. Presumably these high tomodensitometric values are caused by the predominantly necrotic contents of these pseudocysts at their early stage of development (Fig.17). Highly developed pseudocysts, on the other hand, appear as well-delimited spheric formations with thick walls (Figs.18 and 20). Their pancreatic origin is in general easy to indicate, except in the case of very voluminous pseudocysts (Fig.19). In view of the obvious difference in density between these liquid-con­taining masses and the adjacent organs, they are generally quite simple to diagnose.

It is striking that these well-developed lesions remain perfectly de­limited and almost never infiltrate the surrounding structures, ex­cept toward the dorsal abdominal wall. Such infiltrations always have the shape of a comet tail and proceed along an anatomic line of cleav­age (Fig.17). In contrast with the high density of pseudocysts in for­mation, the density of well-established pseudocysts approaches the to­modensi tometric values of renal cysts, i. e. , less than 15 Hounsf ield units.

Carcinoma and Other Neoplastic Processes

Pancreatic tumors can be revealed by CT exploration only if they cause a pancreatic enlargement. It is indeed generally impossible to deter­mine the difference in density between tumoral and normal tissue. Smaller tumoral processes, such as insulomas, ampullomas and even ade­nocarcinomas will not be discovered unless they cause other indirect signs, such as an obstruction of the biliary ducts or of the Wirsung canal (Figs.22 and 23).

Depending on the size and the extent of the tumoral masses, CT can reveal other signs that emphasize even more the malignant nature of the tumor. The most important sign is the localized obliteration of the cleavage planes and the absence of delimitation of the adjacent structures ("silhouette sign") (Fig.21).

A cystadenocarcinoma is a tumor that is liable to be confused with chronic pancreatitis on CT. In view of the frequent presence of cal­cifications and hypodense cystic areas, it can appear identical to a chronic calcific pancreatitis with pseudocystic formations (Fig.24).

Besides the pathology proper to the pancreatic gland, adjacent proces­ses, particularly organomegalies that cause extrinsic compression, can also alter the aspect of the pancreas. These organomegalies can cause the global displacement of the pancreas and thus be responsible for a topographic as well as a morphologic alteration (Fig.25).

201

Conclusions

CT examination is a technique that is easy to use and comfortable for the patient. It makes it possible to visualize the pancreas with a success rate up to 85%. The best results are obtained in the examin­ation of acute pancreatitis and pseudocysts. However, the differen­tial diagnosis between chronic pancreatitis and tumoral processes is extremely difficult, due to the fact that these two pathologies appear under very polymorphic aspects without supplying a single specific sign.

We acknowledge the valuable assistance of Dr. G.A.J. TOPS in the translation into English.

Fig.l

Fig.l. Normal pancreas. This example illustrates the advantage of combining supine position and right lateral decubitus. Diluted gastrographine, administered orally helps distinguish the pancreatic head from the adjacent duodenum ~). Note also the normal turgescence of the inferior caval vein in right lateral decubitus po­sition (-7)

Fig.2. Normal pancreas: left oblique anterior position. In this position the gas­trographine in the stomach perfectly moulds the anterior surface of the body and the tail of the pancreas. Notice that in this position artifacts due to the air­contrast level in the stomach are projected out of the pancreatic shadow

202

Fig.3. Successive cuts of a normal. slightly ascending pancreas. If the pancreatic body and tail are not situated on the same level as the head. the exploration of the pancreatic gland necessitates successive sections to visualize the organ com­pletely. A. Head. B. body. C. tail. The source of the superior mesenteric ar-tery serves as principal landmark for locating the pancreas (---+). After intra­venous injection of a cholangiographic product. the topographic relation between the common bile duct and the duodenum is studied. The biliary ducts are indicated by (~)

203

Fig.4. Normal pancreas : False image of pancreatic head enlargement in the right lateral decubitus position. This study proves that the pancreas, in spite of its retroperitoneal location, preserves a certain mobility, which can occasion a pseudo­enlargement of the head in the right lateral decubitus. In the supine position this false image disappears, because the pancreas spreads itself over the great vessels and the vertebral column. Opacification of the common bile duct (--7) and the gallbladder (~)

Fig.5. False image of pseudocyst in the area of pancreas tail. This image is caused by the verti­cal part of the stomach, filled with liquid. The presence of an air-liquid level allows recogni­tion of the exact nature of this structure

Fig.6 Fig.7

Fig.6. Variability of the volume of a normal pancreatic gland. A short and compact pancreas

Fig.7. Normal variability of pancreatic volume. A long and thin pancreas

Fig.B. An atrophic pancreas in an older patient. In older patients we frequently observe an important involution of the pancreas, without any history of chronic pancreatitis. CT examination by itself does not permit the distinction of this physiologic involution from an atrophic chronic pancreatitis. Notice also the con­siderable lipomatosis in the renal hilus, another sign of senile involution

205

Fig.9. Chronic pancreatitis. The whole pancreas is considerably atrophied and has highly irregular contours. Some calcifications are observed in the tail of the pan­creas

Fig.10. Carcinoma of the pancreatic head. The presence of a neoplastic process in the head of the pancreas is recognized by the mass-effect in this area. Many other indirect signs also suggest a space-occupyjng lesion at this level: dilatation of the intrahepatic biliary ducts <..-) and Wirsung dilatation <~) in the pancreas tail. The obliteration of the peripancreatic fat planes (~) cannot be considered a sign of malignancy in this case, in view of the variability of this feature ac­cording to the position of the patient

206

Fig.11. Carcinoma of the pancreatic tail. Considerable enlargement of the tail of the pancreas with sharply limited cohtours and preservation of the adjacent fat planes. Due to low tomodensitometrical values it was erroneously diagnosed as a pseudo­cyst. This case proves that the presence of artifacts makes the tomodensitometric study very hazardous, sometimes even impossible

Fig.12. Acute pancreatitis. Diffuse enlargement of the whole pancreas without loss of regular contours or obliteration of the peripancreatic fat planes. Notice the shadow of the duodenal loop, incorporated in the image of the pancreatic head when patient is in the supine position, whereas the duodenum is clearly delineated when patient is in the right lateral decubitus position and when intraluminal diluted gastrographine is administered

207

Fig.13. Acute pancreatitis. Besides enlargement of the pancreas, the only anomaly in Fig. 12, this image also shows an infiltration of the peripancreatic fat plane in the form of dense striae. These striae are particularly well visualized on the tail (~)

Fig.14. Acute phase in chronic pancreati­tis. Enlargement of the pancreas, more pro­nounced at the tail with presence of a hypodense, more or less rounded area (~). This probably corresponds to a nascent pseudo cystic formation

208

Fig.1S. Chronic calcific pancreatitis . Calcifications in a moderately enlarged head with very irregular contours

Fig.16. Acute phase in a chronic calcific pancreatitis. The large irregular and hypodense mass in the pancreatic area, containing a few calcifications, is caused by a pseudocystic formation during an acute phase. The rather dense contents of such nascent pseudocystic formations make differentiation from tumoral processes difficult

Fig.18

209

Fig.17. Early stage of pseudo­cyst formation. Unlike well-for­med pseudocysts, a pseudocyst in its formation stage is charac­terized by the presence of less­pronounced hypondense areas and by poor delineation of the pseu­docystic walls. This figure also shows an extension turning around the lateral margin of the left kidney (~) and extending to the dorsal muscular mass, of which different muscles are ede­matous (~)

Fig.18. Pseudocyst of the head of the pancreas. Typical image of a pseudocyst. Round-shaped area clearly hypodense when compared with the adjacent pancreatic pa­renchyma. Note also the thick wall and the clearly delimited and regular contours

Fig.19. Giant pseudocyst. It is almost imposslble to indicate the exact origin of these huge processes N.B.: The impression of a horizontal level one notices at the superior part of the des­cribed mass (~) is an example of an electronic scanning artifact on the T.V. monitor

210

Fig. 20. Pseudocyst of the pan­creatic body. Although CT de­monstrates the extrinsic im­pression on the back side of the stomach very clearly, it can not detect the presence of necrotic material (----?)

in the pseudo cysts as well as echography does

211

Fig.22

Fig.21. Extended carcinoma of the pancreas. Besides the presence of an important solid and irregular mass in the pancreatic region, this examination indicates the existence of metastases in lymph nodes behind the phrenic crura (~)

Fig.22. Carcinoma limited to the pancreas head. Irregular extension into the lumen of the duodenum, opacified with gastrographine (~). Dilatation of the Wirsungian duct (~) caused by obstruction

Fig.23. Ampulloma. The presence of an obstructing lesion is suggested by the dilatation of the common bile duct (~) and gallbladder (~). The ampulloma itself was not visualized by CT-examination

212

Fig.24. Combined pathology: cystadenocarcinoma (~) of the pancreatic tail and chronic cal­cific pancreatitis (~. This example de­monstrates that the presence of calcifications is not necessarily a pathognomonic sign of chronic calcific pancreatitis, since calci­fications and hypodense areas, as well as irre­gular contours, are also found in cystadenocar­cinoma

Fig.25. Hepatic metastases (~), hepatosplenomegaly. Total displacement of all the retroperitoneal organs, aorta, inferior caval vein and pancreas

Kidneys J. Struyven, M. Osteaux, R. Huvenne, and L. Jeanmart

In the past, ultrasound and arteriography have proven to be reliable means of diagnosis. The purpose of this paper is to evaluate the ac­curacy of CT in detection of renal pathology.

Materials and Methods

Investigations are performed using an Ohio Nuclear Delta Scanner which obtains two simultaneous 13 mm thickness slides in 2 min 30 s and has an image matrix of 256 x 256. A cursor circle, variable in size and location, can measure attenuation numbers of any region of interest.

Patients are scanned in dorsal decubitus position without attempting to limit respiratory motion, but motion artifacts are reduced by ad­ministering an antiperistaltic drug, usually 3 mg glucagon I.M. A first series of 8 sections is performed without contrast media. The scanning is repeated after intravenous injection of 50 - 100 cc of urografin 60% in a bolus. Renal investigation represents 6% of total studies and 14% of non-neurologic examinations. Most patients were referred to CT Scan because of intravenous pyelography (IVP) abnor­malities or nunfunctioning kidney. Other patients were investigated for postoperative evaluation, hematuria, clinically suspected neo­plasm, or unproven renal pathology.

Table 1. Patients referred for renal IVP morphologic abnormalities Nonfunctionning kidney Postoperative evaluation "Screening" Other

Total: 157 patients

diseases. 76%

5% 4% 7% 8%

100%

The diagnostic criteria employed in the CT evaluation of the kidney are: (1) alteration of the normal contour, (2) visualization of a renal mass, (3) disappearance of perinephric outline and (4) measure­ments of attenuation coefficient in a region of interest.

The results of CT evaluation are compared with operative findings, punctures, or clinical evidence in 100 cases.

214

Results

Results are listed in Table 2.

Table 2 - Results Normal 13% Renal neoplasm 24% Cysts 40% Adenoma 2% Inflammatory lesion 3% Hydronephrosis 8% Renal aplasia 3% Retroperitoneal disease 4% Other 6%

Total 103%

Normal Kidney

The kidneys are defined well by CT Scan because of the presence of perinephric and sinusa1 fat which provides a clear outline of renal parenchyma. The renal contour is smooth and well delimited from pe­ritoneal structures. A break occurs at the hilus where the vascular pedicle is directed anteromedia11y toward the aorta and the vena cava inferior. The renal parenchyma is homogeneous. After administration of contrast media, the shape of the calyces and renal pelvis is sharp­ly defined. Without contrast media, normal parenchyma has an attenu­ation coefficient of 50 -70 delta units which rises to 100-120 delta units after contrast enhancement. Renal veins are usually visible, but arteries are demonstrated in only about 20% of cases.

Renal Neoplasm

The renal neoplasm produces an alteration of the normal renal outline and usually an enlargement of the kidney. The neoplastic parenchyma appears unhomogeneous and has an attenuation value approximately equal to the normal tissue, but after contrast the tumor enhances far less than the surrounding normal parenchyma. If the normal attenuation equi­valent rises from 60 to 100 delta units, neoplastic tissue reaches 70-80 delta units. Another useful sign is the loss of the fat surrounding the kidney, which most likely represents infiltration of the neoplasm. This sign is reliable in patients of normal size; however, in very thin patients with little fat the sign is less useful. An invo1vment of the hilus is easily recognized.

Of 24 cases 22 were operatively proven: in two patients there was cli­nical evidence of renal neoplasm. In one case there was no CT evidence of renal malignant involvement, but a protruding mass was visible in the hilus. Arteriographic study showed an intrarena1 neoplasm without ex­tracortica1 extension but with hilus extension. The ultrasound diag­nosis was that of a neoplasm. This case is considered a false negative.

Cysts

Renal cysts are sharply marginated, rounded structures on CT scan. Their attenuation value is - 15 to + 15 delta units and does not increase after injection. In this series, most patients were referred to CT be­cause of IVP abnormalities. Renal cysts are a very common finding in patients examined by axial tomography. Cysts of 1 cm are easily seen, when projecting beyond the cortex.

215

Polycystic renal disease is correctly diagnosed if enlarged kidneys with lobulated contours, multiple cysts of variable size, distortion of calyces and remaining parenchyma, and bilaterality of the process are present. The same examination is used to exclude or establish a hepatic location. Cystic lesions can be aspirated under CT control.

Adenoma

The case of adenoma showed a lobulated parenchymal lesion with strong contrast enhancement not occurring in neoplasm. Further experiments are necessary to establish whether this is a pathognomonic sign. Cystadenoma produces an enlargement of the kidney with multiple cysts. Prior to contrast injection the kidney appears unhomogeneous with areas of low density (-15 to +15). After contrast injection, cysts are clearly delimited and surrounded by contrast enhanced parenchyma. We encountered this cystadenoma in a five year old child with a left palpable abdominal mass. Previous examinations, IVP, ultrasound, and arteriography suspected a malignant lesion. During our early experience with CT this case was diagnosed as a multicystic benign lesion.

Hydronephrosis

Whereas IVP is not able to diagnose a hydronephrotic, nonfunctioning kidney, obstructive uropathy is easily recognized by axial tomography. The kidney is enlarged and attenuation value measuring shows low den­sities. If there is still an excretory function, levels of contrast media can be seen in dilated calyces. Moreover, CT is often able to recognize the origin of obstruction, for example, neoplastic involve­ment or calculus.

Inflammatory Lesions

Intrarenal abscesses are visualized by CT as lower density lesions (20-35 delta units) but less sharply delimited than renal cysts. There is no contrast enhancement of the pathologic area. Two cases were cor­rectly diagnosed, the third was a xanthogranulomatous pyelonephritis which appeared to be a cyst by ultrasound and was defined as an in­flammatory mass by CT.

Other Pathologic Processes

With CT every case of atrophy or aplasia of kidney can be diagnosed. Focal renal infarction is characterized by a marginal area which does not show contrast enhancement, and the kidney seems normal prior to contrast injection. Only one case was investigated by CT and proven by arteriography.

Changes from the normal anatomy of the retroperitoneum can easily be recognized, since tumoral masses are well profiled by surrounding fat and the tissue plane of the well defined structures of muscles, aorta, and vena cava inferior are obliterated by any tumoral process or their normal clear delineation obscured. One case of ureteral neoplasm in­volved the right psoas muscle and infiltrated the vena cava as well as the right renal hilus.

CT is very useful in postoperative evaluation of retroperitoneum space for visualizing a recurrent lesion. Post-traumatic study also shows renal rupture and eventual urinary extravasation.

216

Discussion

Three erroneous conclusions were drawn in this study: one false negative was a renal neoplasm without extension and enlargement. In the second case, a large extrarenal pelvis, not opacified by IVP, was diagnosed as a cyst, and because of a slight increase of density after contrast injection, suspected of malignant transformation. Arteriography gave a correct diagnosis. The third case showed an artifactual tumor in front of the lower pole of the right kidney. In five cases a doubtful conclusion was made and two renal neoplasms were demonstrated in pa­tients referred for investigation of another region.

In view of the fact that arteriography and ultrasound have a high rate of accuracy, it was not expected that CT scan would play an im­portant role in renal disease. However, experience shows that CT can visualize most morphologic diseases of the kidney and as a non-inva­sive technique obviates the need for arteriography in a number of cases. CT scan provides an etiologic diagnosis and delimits the extent of le­sions; it is an excellent screening procedure with a high level of ac­curacy.

Bibliography

ALFIDI, R.J., HAAGA, J.R., MEANY, T.F.: Computed tomography of the thorax and ab­domen. Radiology 117, 257-264 (1975)

HOUNSFIELD, G.N.: Computerized transverse axial scanning (tomography). Brit.J. Radiol. ~ 1016-1033 (1973)

SHEEDY, P.F., STEPHEN, D.H., HATTERY, R.R.: Computed tomography of the body. Amer. J. Roentgenol. 127, 23-52 (1976)

STANLEY, R.J., SAGEL, S~, LEVITIT, R.G.: Computed tomography of the body. Amer. J. Roentgenol. 127, 53-67 (1976)

TWIGG, H.L., AXELBAUM, S~, SCHELLINGER, D.: Computerized body tomography with the Acta Scanner. JAMA 234, 314-317 (1975)

Fig.l Fig.2

Fig.3 Fig.4

Fig.1-4. Normal anatomy of kidneys. Aorta (A) Vena Cava Inf. (V) Liver (L) Pancreas (P) Gallbladder (G) Kidney (K) Sup. Mesenteric Artery (MS) Fig. shows vascular pedicules. Fig. 4 shows anterior position of left hilus

Fig.5 Fig.6

Figs.5 and 6 demonstrate typical aspect of renal cysts. The left kidney of Fig.6 is sclero-atrophic

217

218

Fig.7 Fig.B

Fig.7. Polycystic renal disease

Fig.B. Polycystic renal and hepatic disease

Fig.9 Fig.l0

Figs.9 and 10. Typical renal neoplasm. Extent to the left. Inhomogeneous aspect of the neoplasm and less contrast enhancement of tumor: 72 Delta Units

Fig.ll Fig.12

Figs.11 and 12. Five year old boy. Abdominal left mass. Fig.11 without contrast, inhomogeneous aspect and enlargement. Fig.12 after contrast injection: well de­fined cysts and enhancement of surrounding parenchyma - cystadenoma

219

Fig. 13 Fig.14

Figs.13 and 14. 58 year old woman. Fever and urinary infection. Dilatation of calyces and renal enlargement. Attenuation valve is higher than in cysts (34 Delta Units)

Fig.15 Fig .16 Fig.15. 56 year old woman. Hydronephrosis - enlarged kidney with low attenuation value (liquid)

Fig.16. 9 year old boy. Right abdominal mass - non functioning, right kidney by IVP - CT shows an enlarged right kidney and contrast media levels in very dilated calyces: Hydronephrosis

Fig.17 Fig.18

Figs.17 and 18. 72 year old man. Referred to CT Scan because of liver defects by nuclear medicine - CT confirms liver metastasis and shows right renal neoplasm

220

Fig.19 Fig.20

Figs.19 and 20. 42 year old man with hematuria and right back pain. demonstrates a right proximal ureteral stenosis. CT shows a retroperitoneal tumoral lesion which invol ves the vena cava and right psoas musc,le. The diagnosis is a ureteral infil­trating neoplasm

. .

Fig.21 Fig.22

Figs.21 and 22. 62 year old man with hematuria. Ultrasound study demonstrates neoplastic involvement of the right kidney. CT study does not show evidence of renal neoplasm

Fig.23 Fig.24

Figs.23 and 24. 69 year old woman. A sinusal tumor was suspected by IVP. CT shows a low density structure in the hilus (5 Delta U.l and after contrast injection (Fig.24l the upper part of this structure shows an increasing density to 28 Delta Unit. CT conclusion was a suspicion of neoplasm. The true diagnosis was an extra­renal large pelvis demonstrated by arteriography

Retroperitoneal Region G. Marchal, Y. Coenen, and A. L. Baert

Normal Radiographic Anatomy (Figs. 1A-D)

On a transverse axial slice of the abdomen the posterior abdominal wall is composed of the lumbar spine and the lumbar muscles with their different fat planes. The psoas muscles, intimately related to the vertebral body, assume a more symmetric and round form as the slices proceed from the cranium caudad. The great vessels are situated immediately before the vertebral bodies. The aorta is visible as a circular structure, which, on the upper abdominal slices, cannot be distinguished from the medial crura of the diaphragms. On all other slices the aorta is seen distinctly, even the aorto-iliac bifurcation. Below the renal arteries, however, the caliber of the visualized ab­dominal aorta progressively diminishes.

Contrary to the abdominal aorta, the vena cava inferior may show a more oval form, except in the right lateral decubitus position, in which some turgescence without any pathologic significance may be seen. On the upper abdominal slices, the image of the vena cava in­ferior can be separated from the liver shadow only if the vessel is injected with contrast medium.

The kidney and the pancreas are surrounded by an important fibrolipo­matous mass, which constitutes the main element of the retroperitoneal space. Between the vertebral body and the mass of the psoas muscles it is often possible to observe the lumbar nerve roots passing through the intervertebral foramina; they appear as small dense structures surrounded by fat tissue (Fig.2).

The retroperitoneal lymph nodes may be visible as small spherical opacities situated around the great vessels (Fig.3). At the upper ab­dominal level these lymph nodes must be distinguished from the dia­phragmatic medial crura, which may assume the same form. Accurate study of several slices will permit identification of a retrocaval lymph node (Fig.4).

The source of the superior mesenteric artery and the renal veins are easily demonstrated (Fig.1B and Fig.1C).

Technique

The CT study of the retroperitoneal region is performed on an patient in dorsal decubitus with an empty stomach. An injection of an intes­tinal hypotonicum (e.g., glucagon) is given in order to reduce or even eliminate gastrointestinal peristalsis.

IV administration of a small quantity of a uro-angiographic contrast medium is useful, because it allows the visualization of the ureters, which are important landmarks. The contrast medium should be infused in a continuous fashion through a vein of the foot in order to obtain

222

a better opacification of the vena cava inferior. The quantity of iodine contrast medium should be related to the renal function. It is important to avoid a high concentration of iodine in the renal caly­ces and pelvis, because the peristalsis of both structures cannot be inhibited by any drug available at present.

Although the presence of products with more or less marked density like barium sulfate and air may cause disturbing artifacts due to in­testinal movements, the presence of retroperitoneal iodine injected during previous lymphography does not generally interfere with the visualization. On the other hand, the presence of metallic foreign bodies, such as clips, renders the image useless.

Pathology of the Great Vessels

The value of CT in retroperitoneal vascular pathology is rather limit­ed. Atheromatosis of the abdominal aorta is frequently observed, but the detection of this anomaly is of course not an indication for CT. On the other hand, aneurysm of the abdominal aorta can be visualized easily and is a distinct indication for CT. The image is characterized by an important increase in the volume of the abdominal aorta. The aneurysmal wall mayor may not be calcified. With CT an evaluation of the extension of the aneurysm in the cranial and in the caudal direc­tion is possible, as well as a clear demonstration of the spatial re­lationship of the anomaly to adjacent organs. The differential diag­nosis with other retroperitoneal tumors is very easy (Figs.S and 6).

With the intravenous administration of a uroangiographic contrast medium it is frequently possible to distinguish the true from the false lumen of the aortic aneurysm, and thus to reveal the possible presence of thrombotic material. A comparison of the results of angio­graphy and CT indicates the precise extension and real dimensions of the pathologic process (Fig.7). However, presence of a para-aortic adjacent pathology, e.g., prevertebral adenopathies, may cause error, since the aortic border is not sharply delineated in this case and consequently the exact dimensions of the aorta cannot be determined (Fig.8). It is also impossible to distinguish an external impression from an invasion of the great vessels. The appearance of the fat plane is not a sure sign of invasion on the retroperitoneal level.

CT and ultrasonography are both excellent diagnostic methods for de­tecting prevertebral expansive processes. Aortography, however, es­pecially by means of trans lumbar puncture, is not without risk. After translumbar puncture the posttraumatic enlargement of the psoas muscle can frequently be observed. The presence of a retroperitoneal hematoma as well as the extravasation of contrast medium in the prevertebral region are not rare (Fig.9).

Since the form of the vena cava inferior is variable, an external im­pression can only be deduced when a paracaval adjacent mass is also present. But in such a case it seems dubious or impossible to suggest an invasion of the vena cava inferior. The diameter of the vena cava inferior must be evaluated in dorsal decubitus. In the right lateral decubitus position some degree of dilatation of the vena cava inferior is always present but without pathologic significance. A marked in­crease in the volume of the vena cava can also be observed in severe cardiac decompensation and in obstructive syndromes of the vena cava itself (Fig.10).

223

The Pathology of the Lymphatic System

The following signs directly indicate the presence of pathologic re­troperitoneal adenopathies.

1. An increase in size of the lymph nodes.

Attention should be paid to false images (Fig.11) of lymph node en­largement. The adrenal glands, the diaphragmatic crura, and adjacent intestinal loops may be misinterpreted as adenopathies. The differen­tial diagnosis between intestinal loops and lymphadenopathies may be facilitated by previous opacification of the intestine with diluted hydrosoluble contrast medium (gastrografin).

2. The invasion of the surrounding retroperitoneal structures.

The retroperitoneal structures lose their usual sharp delineation (Fig.12). The obliteration of the fat planes surrounding the aorta, vena cava inferior, and psoas muscle is an indication of prevertebral pathology; however, the diagnosis should be advanced carefully in the case of nonobese or emaciated patients, whose fat planes may be absent.

3. A pathologic enlargement of surrounding organs (Fig.13). This can be considered a very valuable sign of invasion by a lymph node mass.

Indirect signs of retroperitoneal lymph node involvement are:

1. Displacement of the kidneys or the ureters to the front or in the lateral direction (Fig.14).

2. Flattening and displacement of the great vessels (aorta and vena cava inferior) (Fig.15).

3. On the higher abdominal level, forward displacement of the pan­creas, indicating lymphadenopathies. An extrinsic impression on the lesser curvature of the stomach sometimes indicates retro­peritoneal adenopathies (Fig.16).

Conclusions

1. Study by CT performed before lymphography permits the visualization of lymph node invasion, but only if these lymph nodes are enlarged. Small lymph node metastasis is therefore not always demonstrated by CT.

2. CT has proven to be of great importance in the study of the superior retroperitoneal level, which cannot be visualized in a satisfying man­ner by lymphography (Fig.17).

3. Lymph nodes on a lower level (pelvic and lumbar), which are excluded from the lymph circulation secondary to total invasion and therefore not visible on lymphography, are easily detected by CT.

Therefore lymphography can be avoided in those cases in which the cor­rect diagnosis has been made by previous lymph node biopsy. CT alone will be sufficient to evaluate the degree of retroperitoneal invasion. On the other hand, due to its poor spatial resolution, CT does not visualize the detailed nodal architecture as seen on lymphography and does not therefore allow a diagnosis of the nature of the invasion. But even if lymphography has been performed previously, CT has its value as a supplementary method: in fact, CT study proves that some

224

pathologic lymph nodes are not opacified by lymphography. In view of its noninvasive nature CT seems to be the best tecnnique for de­fining the fields of irradiation therapy and for making a follow-up evaluation of the effect of treatment on the evolution of lymph node masses.

Adrenal Glands

Radiographic Anatomy (Fig.18).

The adrenal glands are visualized on CT as small opacities on the level of the upper pole of the kidneys surrounded by perirenal fat tissue. The left adrenal gland, easily recognized by its triangular form, is situated before the upper renal pole. The right adrenal gland, on the contrary, is more difficult to identify and must be sought halfway between the vena cava inferior and the superior pole of the right kidney.

Pathology (Figs.19-22).

Although the adrenal glands can frequently be visualized it is still difficult to evaluate the degree of hyperplasia. On the other hand, adrenal tumors can generally be easily visualized. It may be some­what more difficult to determine their exact origin and to differen­tiate them from tumors originating from the tail of the pancreas or from the upper pole of the kidney.

Although most of the lesions with calcified walls occurring in the adrenal space are benign cysts, some malign, largely necrotic, tumors may assume the same appearance. Density measurements are helpful in defining the liquid or solid nature of the mass.

Pathology of the posterior Abdominal Wall and the Retroperitoneal Fibro1ipomatous Tissue

Infectious and tumoral processes, either primary or secondary, may be present in this area, where the possibilities of differential diagnosis by CT greatly exceed those of conventional methods. Indeed with CT the muscles of the posterior abdominal wall, the retroperitoneal organs, and the fibro1ipomatous tissue can be directly visualized.

Study of the exact topography of these lesions and their relationship to surrounding organs frequently makes it possible to differentiate between a primary pathologic condition and the extension of the con­dition by contiguity. Moreover, some specific CT characteristics per­mit a diagnosis of the nature of the lesion (infectious or tumoral) (Figs.23-25).

We acknowledge the valuable assistance of Dr. G.A.J. TOPS in the translation into English

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225

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KORMANO, M., DEAN, P.B.: Extravascular contrast material: the major component of contrast enhancement. Radiology 111, 379-382 (1976)

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MCCULLOUGH, E.C., COULAM, C.M.: Physical and dosimetric aspects of diagnostic geometrical and computer-assisted tomographic procedures. Radiol. Clin. North. Am. XIV, 3-14 (1976)

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PALMERS, Y., BAERT, A.L., MARCHAL, G., COENEN, Y.: Computed tomography (CT) in affections of the vertebral column and of the spinal cord. J. belge Radiol. ~ 521-530 (1976)

PHILIPS, R.L., STEPHENS, D.H.: Computed tomography of liver specimens. Radiology 115, 43-46 (1975)

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A

C

227

Fig.1A. Abdominal cut at the level of Th 12 - L 1. Visualization of the liver with vena cava inferior incorporated into the liver silhouette. At this level the lobus caudatus (~) protrudes into the direction of the aorta. The anterior border of the abdominal aorta (~) cannot be separated from the diaphragmatic pillars. The image of the superior pole of the left kidney cannot be separated from the splenic shadow

Fig.1B. Abdominal cut at the level of L 2. On both sides of the vertebral column the round kidney opacities appear, surrounded by the fibrolipomatous tissue of the adipose capsule. The origin of the superior mesenteric artery ( ) is demonstra­ted, as well as the pancreas. The opacification of the gallbladder and the duo­denal arch (~) is caused by previous intravenous cholangiography

Fig.1C. Abdominal cut at the level of L 2 - L 3. Visualization of the renal veins. The left renal vein (~) passes through the mesenteric-aortic space. The left renal pelvis is opacified. The superior mesenteric artery is indicated by (~)

Fig.10. Abdominal cut at the level of L 4. This cut is situated at the level of the inferior poles of both kidneys, which show unsharp borders due to the tan­gential incidence of the X-rays. The small opacities situated behind the great vessels probably represent normal lymph nodes

B

o

228

Fig.2. Lumbar nerve roots (~) surrounded by a small layer of hypodense fibro­matous tissue

Fig.3. Normal lymph nodes (~). The third sector of the duodenal arch passes between the vena cava infe­rior and the aorta on one side and the mesenteric ar­tery (~) and vein (~) on the other side

229

Fig.4 Fig.5

Fig.4. Serial cuts of the superior retroperitoneal region. On the superior slices the pillars of the diaphragma surround the aorta. On the inferior slices the pil­lars become smaller and are reduced to small opacities which are adjacent to the anterior border of the vertebral body. The section of the right diaphragmatic pillars (~) must be differentiated from a retrocaval ganglion. The flattened vena cava inferior is represented by a small dense ribbon

Fig.5. Abdominal aortic aneurysm with calcified wall extending into the common iliac arteries (~)

230

Fig.6. Upper abdominal extension of an aneurysm with calcified borders. Con­siderable displacement of the dia­phragmatic pillars. The relation be­tween the vena cava inferior and the lobus caudatus of the liver (---+) is clearly visible

Fig.7. Abdominal aneurysm with thickened wall. Proving the presence of a false lumen, CT thus deduces the presence of thrombotic material. The true lumen is in­dicated by a hyperdense area due to the presence of intravenously administered contrast medium (--?). The arteriography suggested the aneurysm but did not de­monstrate it clearly. The levels o{ the CT slices are indicated on the image of the aortography

Fig.S. Abdominal aneurysm and lymphadenopathies; combined prevertebral pathology. CT could not differentiate between an abdominal aortic aneurysm alone and prever­tebral adenopathies causing the disappearance of the aortic border. In this case, the presence of vascular pathology was proven by both ultrasonography and aorto­graphy

Fig.9. CT after trans lumbar aortography. Ex­tensive hematoma in the psoas muscle and the retroperitoneal fat tissue. The psoas muscle is increased in size and its outline is blurred (~). The small dense area behind the psoas muscle is caused by effusion into the fat tissue (~). Extravasation of the preaortic contrast medium (~)

232

Fig.10. Cardiac decompensation. Dilatation of the vena cava (~), which is visualized in the form of a hypo dense area behind the lobus caudatus of the liver. Venae hepa­ticae (~) are dilated. Same finding observed on the ultrasono­gram

Fig.11. Hodgkin's disease. Several spherical opacities are present in the prevertebral region. The lympho­graphy shows several enlarged lymph nodes with evident lacunar images. Note that the level of this CT slice is situated at the renal hilus, a level at which most lymph nodes will not be opacified by lympho­graphy

233

Fig.12 Fig.13

Fig.12. Lymphosarcoma. Lymph node pathology in this case is proven, not only by the presence of an abnormal pathologic mass lesion, but also by the obliteration of the fat planes between aorta, vena cava and psoas muscles. The retroperitoneal elements are no longer individually visible

Fig.13. Hodgkin's disease. Increase in size of the psoas muscle by invasion of Hodgkin tissue (~), originating in the para-aortic lymph nodes. Dilatation of the left renal pelvis caused by a low ureteral obstruction

Fig.14. Lymph node metastasis of a testicular seminoma. Presence of several poly­lobulated masses displacing the inferior pole of the right kidney (~). In con­trast with the previous figures (Figs. 12-13), the fat planes are still present

Fig.16

Fig.IS. Retrocaval and retro-aortic lymph node metastasis. Flattening of the inferior vena cava, which is dis­placed to the front (~) as is likewise the right renal vein (~)

Fig.17

Fig.16. Hodgkin's disease. Large pre-aortic mass, displacing the whole pancreatic gland to the front

Fig.17. Hodgkin's disease. Presence of a small para-aortic ganglion at the level of L 1, displacing the right diaphragmatic pillar to the front

235

Fig.18. Normal adrenal glands. Case A. Good visualization of both adrenal glands (~). Case B. Only the left adrenal gland situated in front of the left kidney is visible. On this slice the right adre­nal gland is not visualized

Fig.19. Benign cyst of the left adre­nal gland. Large spherical mass situa­ted above the superior pole of the left kidney. Fluid density of the mass.

Fig.20. Adenoma of the left adrenal gland. Small spherical opacity si­tuated on the left lateral side of the aorta (~). The superior pole of the left kidney is visualized as a faint density behind the adrenal adenoma

Fig.21. Bilateral adrenal carcinoma. gland. Small spherical opacity sit­uated on the left lateral side of fect the fat planes. The benign or malign nature of the lesion cannot be predicted by CT alone

237

Fig.22. (A) Calcified adrenal carcinoma. In this case of a calcified adrenal tu­mor the central location of the calci­fications suggests a solid and malign nature. Locoregional extension of the tumor towards the aorta and the left diaphragmatic pillar. (B) Benign adre­nal cyst with a calcified peripheral rim, displacing the right kidney me­dially

Fig.23. Retroperitoneal amoebian ab­scess. A large mass behind the left kidney, intimately related to the muscular wall. The kidney is dis­placed to the front. The persistence of a fat plane between the mass and the kidney excludes a renal origin. The mass itself has a thick wall and a hypodense central area, indicating its liquid content

238

Fig.25

Fig.24. Idiopathic retroperitoneal fibrosis. Behind the left kidney, which is displaced to the front an abnormal structure in the form of a belt is visible. The muscles of the left abdominal wall are enlarged. The persistence of the fat planes and the enlarged aspect of the adjacent structures suggest the inflam­matory nature of the mass rather than a tumorous· infiltration

Fig.25. Serous retroperitoneal cyst. Mass with cystic characteristics: low density, spherical form and sharp borders. The persistence of the fat plane between the mass and the right kidney proves the extrarenal origin

Pelvis G. Marchal, Y. Coenen, and A. L. Baert

Technique

A routine examination of the pelvis by means of CT is carried out with the patient, who has fasted prior to examination, in the supine po­sition. Intravenous injection of a hydrosoluble contrast medium, ne­cessary to opacify ureters and bladder, must precede the CT session by 1 h - 1 1/2 h to obtain a sufficient filling of the bladder. Since a high concentration of contrast medium in ureters and bladder can cause undesirable artifacts, simultaneous oral or parenteral adminis­tration of fluid is indicated.

At the level of the pelvis, the supine position alone is usually suf­ficient for solving most of the problems, but the prone position can also be useful in cases of anterior bladder wall lesions. Indeed, a complete visualization of the entire bladder in one position is im­possible if sedimentation of the contrast medium occurs. To obtain a more precise view of the rectum and the sigmoid, a small amount of diluted gastrografine may be introduced, but insufflation of the rec­tum and the colon should be avoided due to the major artifacts caused by the extremely low density of the insufflated air which yield poor results.

Normal Radiographic Anatomy

The presence of fairly large amounts of fatty tissue generally renders easy the study of the different normal anatomic structures of the bony pelvis and the adjacent muscles. The position of great vessels, such as the aorta, vena cava, and iliac arteries and veins, is easy to identify on the different cuts. On the other hand, it is much more difficult to locate exactly the normal lymphatic system and the tor­tuous internal iliac vessels.

Among the proper pelvic organs, the bladder and the rectum can easily be recognized in both sexes •. However, since neither prostate nor uterus can be differentiated from the bladder on the plain studies, previous bladder opacification is always necessary. The genitals can only-rare­ly be distinguished from the adjacent intestinal structures.

Pathology

Pelvic pathology can be divided into three areas:

1. Pathology of the pelvic wall. 2. Pathology of the vessels and lymphatic system. 3. Pathology of the true pelvic organs.

240

Pathology of the Pelvic Wall

The pelvic wall is composed of bony and soft tissue, muscles, and fat.

Pathology ot the Bones: Conventional radiography allows easy detection and precise description of large osseous lesions. Small osteolytic lesions, however, can be missed because of overlying intestinal gas. In some cases, they are detectable only by isotopic studies but not by standard radiography. At this stage, CT seems to be more sensitive than conventional radiotomography, but because of its rather low spatial resolution a detailed description or a highly specific diag­nosis of even large lesions has so far remained impossible. Neverthe­less, in cases of large osseous processes, CT can be useful, showing better than any other method available the extension of the osseous process into the soft lesions.

Pathology of the Soft Tissues: In this field the contribution of CT is of great significance indeed, since it is presently the only avail­able method allowing a precise anatomic study of soft tissues, such as muscles as well as fibrous and fatty tissue. The contribution of CT is essentially on the topographic level, precisely delineating localiza­tion and extension of the pathologic processes. The exact nature of these processes, however, is frequently difficult to define. Both metastasis in muscle and inflammatory lesions show the same aspect: the involved structures appear enlarged, their contours blurred, and fatty tissue planes are lost. The same symptoms, together with zones of low density, which indicate liquid contents, suggest abscess for­mation.

Pathology of the Vessels and Lymphatic System

Among the vascular diseases, only arterial aneurysms constitute real indication for CT investigation. At the level of the pelvis they are mostly extensions of aortic aneurysms. Any association of a mass on the scans with calcifications in its periphery is highly suggestive of this disease.

Although CT is relatively unimportant in the detection of vascular pathology, its possibilities in the exploration of the lymphatic sys­tem are extensive. Pathologic lymph nodes, either lymphomatous or metastasic, have the same appearance of rounded or oval masses along the iliac vessels. Due to the small volume of the pelvis, they rapidly encroach on the pelvic organs, causing supplementary signs of extrinsic compression or invasion.

Compa~ed with lymphangiography, CT seems more valuable for detecting secondary metastasis; however, this is not so in the localization of lymphomatous nodes. Large metastasic lymph nodes, which remained non­opacified in lymphangiography are indeed rather frequent findings on CT studies.

Because of its noninvasive character, CT is also the method of choice for the follow-up studies of patients during and after treatment for ganglionic involvement.

241

Conditions of the Pelvic Organs

Bladder: One major problem in the tumoral pathology of the bladder is the exact evaluation of tumor extension: extension into the bladder lumen is easily demonstrated by conventional cystography; however, the prediction of extravesical tumor invasion is rather hazardous. CT now appears essential for solving this specific problem, since it can clearly demonstrate the exact degree of extension (none, limited to the wall, or encroaching on the perivesical tissue). However, its li­mited spatial resolution and the fact that prostate and uterus can only be studied indirectly makes it impossible to differentiate a primary bladder tumor with extravesical extension from a secondary bladder invasion by a prostate or uterus neoplasm.

Prostate: Study of the prostate always requires previous bladder opa­cification. All prostatic tumors, benign as well as malignant, are visualized in the same way as more or less regular retrovesicular mas­ses encroaching on the posterior bladder wall. The exact nature of these processes cannot generally be predicted from the CT image alone, except in those cases in which infiltration or extension outside the bed of the prostate (e.g., invasion of the ischiorectal fossa) can be demonstrated.

uterus and Vagina: Here too, the aim of CT is not to make a specific diagnosis, but rather to evaluate the extension of the pathologic pro­cesses thus benefitting a precise plan of therapy. The CT signs of tumor and focal invasion are the same as elsewhere in the body: an abnormal mass is found, with or without loss of the adjacent fat planes, signalling a tumoral breakthrough.

Ovaries: At the midlevel of the pelvis, relatively fixed organs, such as bladder and rectum, provide valuable topographic landmarks, permit­ting in most cases the precise identification of the localization and the origin of the pathologic processes. The absence of these land­marks at the superior pelvic level, however, gravely impairs the topo­graphic precision of CT. It is therefore difficult to determine exactly the origin of a mass at this level, especially in the case of space­occupying lesions originating in the uterus and ovaries.

Cystic masses of the ovaries also present a problem. Elsewhere in the body, cystic masses are generally benign, but in the pelvis benign multilocular cysts have the same appearance as cystadenocarcinomas (polylobular, low-density lesions with multiple septations), so that a differential diagnosis by means other than CT is necessary.

Rectum: The indications for CT are identical with those of the vagina and uterus: CT permits evaluation of operability according to the peri­tumoral extension.

Conclusions

In theory, the pelvis should be very suitable for CT investigations, since, for instance, the influence of respiration on the pelvic organs is rather limited and thus causes few artifacts due to motion; in practice, however, the results are not completely satisfactory.

The major indications seem to be the following:

1. Study of the pelvic wall, useful in surgical or radiotherapeutic planning.

242

2. Detection of pathologic lymph nodes and follow-up evaluation during treatment.

3. Topographic study of the tumoral pathology of the pelvic organs and their extension.

A specific diagnosis, however, is frequently difficult and hazardous.

We acknowledge the precious aid of Dr. G.A.J. TOPS for the translation into English.

Fig.1. Primary bladder tumor or~g~­nating from the right anterolateral wall. In the supine position the tumor is visualized as a rather dense but restricted thickening of the bladder wall, contrasting with the low density of the urine. In this position the se­dimentation of the contrast medium o nly permits the study of the poste­rior bladder wall. The internal de­limitation and the irregularity of the wall are better demonstrated in the prone position

Fig.2 Fig.3

Fig.2. Adenocarcinoma of the endometrium. Anteversion of an enlarged uterus, en­croaching on the opacified bladder. The ligamentum teres is demonstrated on the right

243

Fig.3. Osseous metastasis of a Ewing sarcoma of the left scapula. Large osteolytic lesion of the left iliac bone, which leaves the sacro-iliac joint intact. Invasion enlarges the iliopsoas and gluteal muscles

Fig.4. Primary Ewing sarcoma of the right iliopubic bones. Compared with the dis­crete signs on conventional radiography, CT shows a large soft tissue mass ori­ginating from the bones, viz. an intrapelvic tumoral extension . (Al CT study, (Bl plain RX films, (Cl lymphangiography

244

Fig.S Fig.6

Fig.S. Chordoma. Complete destruction of the sacrum by large tumoral mass, in which some osseous elements can still be found. The process appears limited and leaves the adjacent fat planes intact

Fig.6. Neurofibroma. Rounded mass of rather low density ( - 20A) eroding the an­terior sacrum and encroaching on the posterior bladder wall. The persistence of a fat plane between both indicates the abscence of tumor invasion or infiltration. The rectosigmoid is displaced to the right

Fig.? Hemangiosarcoma. Besides the cystic aspect of the sacrum, the CT study shows intrapelvic tumor exten­sion with extrinsic compression of bladder and rectum

Fig.8 Fig.9

Fig.8. Perineal rhabdomyosarcoma. Obliteration of the left fossa ischorectalis by an irregular tumoral mass

245

Fig.9. Metastasis in the anterior abdominal wall. Cut at the superior pelvic level. Large space-occupying lesion, situated in the muscular wall (left musculus rectus abdominis). Infiltration of the adjacent fatty tissue (dense striations and nodules)

Fig. 10. Phlegmon. Thickening of the musculus obturatorius internus and ex­tension muscles. Loss of fat planes due to infectious infiltration. A differen­tial diagnosis between an infectious and a tumoral process on the basis of numeral denSitometry is difficult

246

Fig.ll. Aneurysm of the right iliac artery. Considerable displacement of the bladder by a round formation with a partially calcified periphery. In contrast with echotomography, CT did not visualize the false lumen in this case

Fig.12. Lymphosarcoma. Involvement of the external iliac nodes, not visu­alized by lymphangiography. The nodes are considerably enlarged. Notice the two opacified nodes

247

A

B

Fig.13 Fig.14

Fig.13. Hodgkin's disease. Greatly enlarged lymph nodes in the left iliac region, only partially opacified by lymphography

Fig.14. Hodgkin's disease. Therapeutic evolution: (A) before, and (B) after radio­therapy. Marked involution of the partially opacified nodes

248

Fig.iS. Metastasic node involvement of a malignant ovarian tumor. Despite the neg­ative lymphangiographic findings at the level of the left iliac region, numerous enlarged metastasic nodes are demonstrated by CT . One of them is encroaching upon the lateral bladde r wall. (Al CT study. (Bl Opacified bladder. (Cl Pedal lympho­graphy

Fig.16. Bladder papillomatosis. Large papilloma protruding into the bladder without local or regional extension

249

Fig.17 Fig.1S

Fig.17. Primary bladder neoplasm. Infiltrating tumor originating from the anterior wall, and with local extension limited to the wall itself, as is indicated by the persistence of the adjacent fat planes

Fig.1S. Primary bladder tumor. Primary tumor originating from the anterior wall, protruding far into the lumen. The blurred delineation on the right highly suggests local invasion of the perivesical fatty tissue

Fig.19

Fig.19. Malignant tumor of prostate. Noticeable enlargement of the prostate. The irregularity of the posterior bladder wall indicates a malignant process rather than a benign hyperplasia. A specific diagnosis, however, remains tentative

Fig.20. Adenocarcinoma of the endometrium. Enlarged uterus. Partial obliteration of the fat plane between uterus and pelvic wall. A solid mass contiguous to the iliac bone: malignant breakthrough to the right pelvic wall

250

Fig.22

Fig.21. Calcified myoma of the uterus. Large, well-defined mass behind the opa­cified bladder and on the right, with some central calcifications. A small lesion of low density appears on the left; it is a small benign ovarian cyst

Fig.23

Fig.22. Carcinoma of the cervix. Large and irregular solid mass that cannot be dissociated from the rectum. The fatty tissue between the mass and the left pelvic wall is infiltrated, as indicated by the higher density at this level. However, cervix and uteral involvement cannot be differentiated

Fig.23. Solid carcinoma of the ovary. A space-occupying lesion and its topographic extension are both clearly demonstrated. The enlarged uterus is visible in front of this mass. It is impossible to determine with certainty whether there is ex­tension to the uterus and the gas-filled rectum. However, infiltration of the right pelvic ureter, opacified by the intravenous contrast medium, is certain

Fig.24. Benign multilocular cyst of the left ovary. Large intrapelvic mass of fairly low density. The mul­tiple septations denote the multi­cystic nature of the lesion

251

252

Fig.26

Fig.25. Cystadenocarcinoma of the left ovary. Huge intrapelvic mass of mixed com­position, partially solid, partially cystic, displacing the bladder to the left. Though its appearance is the same as that of the cyst shown on Figure 24, it is a malignant cystadenocarcinoma

Fig.26. Primary adenocarcinoma of the rectum. The circular tumor revealed by the ~study is also obvious on scan. The large solid mass in front of the bladder was caused by an intraperitoneal metastasis

Fig.27. Local relapse of an adenocarci­noma of the rectum after abdominoperi­neal resection. Large mass with malig­nant features partially destroying the sacrum, but with only minimal displace­ment of the uterus

Abdominal Computer Tomography and Contrast Media R. Huvenne, A. Grivegnee, J. Struyven, M. Ostreaux, L. Jeanmart, and A. Bollaert

CT is a good method for reproducing both morphology and internal structure of human organs. To be efficient CT should provide both sharp outlines of structures and accurate densitometric measurements. This means that a fine spatial resolution and simultaneously, if possible, an accurate densitometric resolution are required. The limitations governing picture quality and relationship to that which is being visualized have already been pointed out by G.N. HOUNSFIELD and will not be treated here.

The densitometric resolution depends on the following factors:

1. The number of measurements obtained. Accurate measurements are directly proportional to this number which varies according to the system used: - 25,000 - 35,000 for so-called first generation scanners, - 100,000 - 500,000 (during overscan) for so-called second gen-

eration scanners, - 100,000 - 300,000 for so-called third generation scanners.

2. Accuracy of the measurements made varies according to the relation­ship:

\!patient's X-ray Dosage x Pixel Volume x Thickness of the cut

Thus, with increased dosage and/or with a coarser matrix, the picture grain is improved. The more photons that arrive at the detectors after penetrating the body, the smaller is the standard deviation and thus the more accurate the information.

The spatial resolution depends on the following factors:

1. The matrix size. The finer the matrix, the greater the number of picture points {a 320 x 320 picture has a spatial resolution of 1 rom between picture points) but, unfortunately, the greater the grain amplitude of the picture.

2. For ultimate visualization of a detail, size and contrast are closely related entities. The modulation transfer function repre­sents the decrease of contrast in reproducing a sinusoidal pattern with increasing periodicity.

A detail becomes perceptible only when its contrast with respect to its background possesses a certain minimal value. If the contrast is reduced below that value, the detail will have to be larger in order to be still discernible. Conversely, a greater contrast enables a smaller detail to be seen.

254

The spatial resolution and accurate readings depend on the choice of matrix, which is also related to the intrinsic contrast of the struc­ture to be viewed. The greater the intrinsic contrast, the more the matrix size can be increased without impairing accurate readings. The converse applies if the intrinsic contrast is low with respect to its background. Consequently, since the perception of detail depends on the grade of intrinsic contrast, it is logical to try to improve it by injection of radio-opaque material.

Several conventional hydrosoluble contrast media were tested to de­cide the amount necessary for an optimal viewing of small details. For each contrast media a "reinforcement value" was calculated, which represents the relationship between attenuation numbers with contrast media and attenuation numbers without contrast media on the same organ of the same normal patient. As many measurements as possible were made for each case.

This relationship is expressed by the formula:

R Densitometry with contrast Densitometry without contrast

Of course, such measurements have no real absolute value, but enough comparisons of measurements with and without contrast media have been made to confer to the relationship a significant value. Using a so­called first generation CT, "slow" scanner, we found that a 60% so­lution of opaque material is the most convenient. Above this concen­tration even with addition of glucagon, highly contrasted structures that are associated with persistent, slight peristaltic movements pro­duce severe artifacts which ruin densitometric pictures.

Measurement Records

Pancreas

After the injection of 100 cc urografine 60% in a normal patient a reinforcement value of 1.6 was determined, meaning that structural details of the pancreas appear more clearly after intravenous ad­ministration of contrast. Experience shows that the examination should be made with the patient in right lateral decubitus position, which delineates the outlines of the organ best.

In the normal patient, we found the following reinforcement values:

- biloptine: 1. 1 - 50 cc urografine 60% : 1.25 - biligram : 1.26 - 100 cc urografine 60% : 1.5

255

Kidney

The main problem in the field of kidney CT is the peristaltic acti­vityof the excretory structures'which cannot be completely sup­pressed. Dosages higher than 50 cc urografine 60% produce so many artifacts that the densitometric picture cannot be interpreted. In a normal patient, the reinforcement value of 2.27 is obtained using 50 cc urografine 60%.

The reinforcement value in some pathologic cases was calculated with the following results:

1.0 in cystic disease of the kidney. 1.5 in neoplasms. 1.1 in adenomas.

The difference of the reinforcement value between benign and malignant masses suggests that CT could determine the eventual malignity of a kidney lesion.

Conclusion

The use of contrast material is presently of paramount importance for obtaining fine structural details in CT examination, leading to more exact and more accurate diagnosis. Their use is somewhat limited with first generation CT for the reasons pOinted out above, the use of con­trast material with the third generation CT will provide more exact information. Future progress in the field of new contrast material selectively metabolized by a given organ is to be expected.

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emulsified ioddifids. Preliminary 41-48 (1976)

the Brain and Orbit (EMI Scanning).

SAN JUAN, Puerto Rico: Advances in CT. Report on the International Symposium and Course. Fortschr. Med. .2.!, 1301 (1976)

WING, S.D., NORMAN, D., POLLACK, J.A., NEWTON, T.H.: Contrast enhancement of cerebral infarcts in computed tomography. Radiology 111, 89 (1976)

Contrast

100 0'..,.. __ _

10%

4°/.

Fig.2

frequency (line pairs/em)

Fig.3

Fig.1. Modulation transfer function (M.T.F.) of sinusoi­dal pattern with increaSing frequency, the contrast is 100% at frequency O. The curve covers the whole contrast range from 100-0%. As the human eye can perceive 4% contrast, 30 per/cm would be distinguishable

Figs.2 and 3. No abdominal structure can be distinguished in this patient due to a great amount of peritoneal fluid. Note on Fig.3: predominance of artifacts due to slight peristaltic movements

257

Fig.4 Fig.5

Figs.4 .and 5. In this patient the lack of differentiation between left liver lobe and stomach (Fig.4) can be misinterpreted as an abscess of the left liver lobe. Figure 5 after administration of contrast medium shows clear delimitation be­tween stomach and left liver

Fig.6 Fig.7

Fig.6. Pancreas without IV contrast in dorsal decubitus position

Fig.7. With IV contrast (right lateral decubitus): three dilatations of the Wirsung canal are visualized

258

Fig.S Fig.9

Figs.S and 9. In this patient, the presence of blood vessels within the tumor makes the hepatoma less obvious than is the case without contrast, because the contrast media enhances the tumor to a density close to that of the normal liver. It seems that IV contrast media is more efficient than contrast material taken orally. Also the reinforcement effect appears greater after injection of 100 cc rather than 50 cc of the same contrast agent

Fig . 10' Fig.l1

Figs.10 and 11. Poor visualization of pathologic right kidney due to lack of con­trast in Figure 10. With contrast (Fig.ll) the kidney cyst containing a clot of blood from a previous unsuccessful puncture is visible

Subject Index

Abdominal wall 226 Abscess 81, 99, 128, 131, 136, Acromegaly 22 Adenoma 26, 28 Adrenal gland 225, 226,

adenoma 238 carcinoma 238, 239 cyst 226, 237, 239 hyperplasia 226 tumor 226

Abscens hepatic 170, 188 subphrenic 170

Ampulloma 200, 211

237

242

Anatomy (pancreas) 197, 198, 201-204 (pelvis) 241 (retroperitoneum) 223, 229

Anesthesia 15 Aneurisma 39, 43, 81, 156 Aneurysm 224, 231-233, 242, 249 Angioma 43, 84, 122, 156 Angulation 16 Aqueduct of sylvius 41 Arachnoid cyst 34 Artefacts 224, 241, 243

(in CT-examination) 197, 201 Ascites 171 Atrophy 47, 50

(pancreas) 198, 199, 204

~iliary cysts 171 tractdilatation 171, 188

Bladder 241, 243, 245 Bone 19, 20, 22, 23, 25, 31-33, 36, 59,

62, 68, 85, 87, 91, 93, 142, 150, 153 (pelvic) 242, 246

Brain stem 26, 66 Bullet 34

Calcification 28, 29, 32, 40, 41, 53 Carcinoma 200, 205, 206, 211 Cavernous angioma 172

plexus 15 sinus 34

Cerebellar tumor 68 Cerebello-pontine lesions 79, 99 Cervical canal 104 Chest 162, 164

(Ct aspect of normal structures) 162 Chordoma 17, 31, 55, 246 Cirrhosis 170 Cisterns 20

Colloid cyst 41 Contrast enhancement in kidney 258

in liver 257 in pancreas 257

medium 257 Corpus callosum 40, 45 Cranio-cervical region 95 Craniopharyngioma 29, 30, 45, 54 Cylindroma 33 cyst 27, 34, 40, 49, 50, 66, 86 Cystadenocarcinoma 200, 212, 243, 255 Cysts (ovarian) 243, 253, 254

E.andy-walker 78 Dermoid cyst 66 Detectors 2 Diagnostic criteria (pancreas) 198, 199

(retroperitoneum) 225 Diaphragma pillars 223, 225, 229, 231,

236 Diverticulum 38

~dema 47, 117, 128 Empty sella 15, 17, 20-23, 38 Encephalitis 134 Enhancement 16, 38, 63, 74, 76, 114,

120, 122, 128, 131, 147, 156 Eosinophilic granuloma 148 Ependymoma 54, 66, 68, 76 Epidermoid 30, 31, 66, 80, 88-90, 113,

139 Ewing sarcoma 245, 246 Exophtalmos 147 Extracerebral tumor 59, 67

Fahr 53

Qlioma 40, 44, 45 Glomus jugular-tumor 96 Graves disease 148 Grey matter 6, 10

~aemangiosarcoma 247 Head 13 Hemangioblastoma 68, 76, 77 Hemangioma 148, 152 Hematoma 40, 46, 51, 68, 78 Hemochromatosis 187 Hepatitis 170 Hepatocarcinoma 172 Herpetic encephalitis 135, 138 Hippel-Lindau 66, 68

260

Histogram 59, 60, 104, 111, 112, 158 History 3 Hodgkin 234-236, 250 Hydatid cysts (liver) 171, 188 Hydranencephaly 49, 52 Hydrocephaly 47, 67 Hydronephrosis 215, 220 Hygroma 49

Infarct 113 Infections 54, 117 Inflammatory disease. 131 Insulinoma 200 Intraventricular tumor 59 Ischemia 41, 49, 113 Ischiorectal fossa 243, 247

ydneys 213

Leukemia 55 Lipoma 40 Liver (contrast mediums) 170, 185

(examination method) 169, 185 (extrinsic invasion) 173 (normal CT anatomy) 169, 186 (primary tumours) 172, 188 (trauma) 171, 189

Lungs 163 Luxury perfusion 115 Lymph nodes 225, 226, 230, 234-236,

242, 244 Lymphography 225, 226 Lymphosarcoma 235, 249

~agnification 62, 64, 159 Maximal density 59 Mediastinum 163 Medullar canal 104 Medulloblastoma 66, 73 Melanoma 148, 152 Meningioma 32, 39, 42, 54, 59, 67, 75,

90, 102 en plaque 142

Mesencephalon 44 Metastasis 46, 66, 77, 97, 126-128, 151

(hepatic) 172, 188 (lungs) 163 (pelvic) 242, 247, 251, 255 (pleural) 164

Microadenoma 15, 17, 23 Microangioma 40, 44 Midline lesions 39 Modulation transfer function 256 Mucocele 35 Myoma 253 Myositis 148

~eoplasm bladder 243, 245, 252 cervix 253 prostate 243, 252 rectum 243, 255

uterus vagina

243, 245, 252 243

Neurinoma 59, 62, 73, 74, 84, 85, 100 Neurofibroma 246 Normal kidney 214

Oligodendroglioma 40 Ophtalmology 147 Optic nerve atrophy 147 Osseous lesions 242, 245 Osteoma 148 OVaries 243, 251, 253

Pancreas 185, 197, 212, 225, 226 (contrast mediums) 185 (examination method) 185 (normal anatomy) 186

Pancreati tis acute pancreatitis 199, 200, 206, 207 chronic calcified pancreatitis 199, 200, 205, 208, 212 chronic pancreatitis 198-201, 204, 207

Papilloma 63 Papillomatosis 251 Papilloedema 147 Parietal lesions 164 Pediatry 47 Pelvis 241, 255 Phacomatosis 54 Phlegmon 248 Pineal gland 40 Pinealoma 46, 72 Pituitary gland 38 Pleura 163 Pleural effusion 163, 164 Polycystic renal disease 215, 219 Porencephaly 50, 121 Posterior fossa 65 Prevertebral adenopathies 224, 225, 233 Profile 61, 105, 110, 145 Prolactin adenoma 23, 25 Prostate 243 Pseudocyst 19·9-201,203,206-210 Psoas muscles 224, 233 Purulent meningitis 136 Pyonephrosis 220

~ecklinghausen 36, 37, 87, 102 Rectum 241, 243 Recurrence 14, 77, 101-103 Renal adenoma 215

cyst 214, 218 cystadenoma 215, 219 infarction 215 neoplasm 214, 219, 220

Resolution (picture resolution) Densitometric 256, 257 Spatial 256, 257

Retinoblastoma 72 Retroperitoneal 223, 240

Re~roperitoneal,

abscess 239 cyst 240 fibrosis 240 tumor 215

Retroperitoneum Rhabdomyosarcoma

amoebian

215 247

~arcoma 33, 98 Sellar region 14 Septum lucidum 40 Shunt 48 Silhouette sighn 199, 200 Soft tissue (pelvic) 242, 246 Steatosis 187

(hepatic) 171 Subarachnoid bleeding 40

!.echnology 2 Tentorium 65, 94 Teratoma 66 Tuberculoma 133, 137 Tuberculous meningitis 133 Tuberculum sellae 42 Tumor 199, 200, 201, 208

!!.terus 243

Vagina 243 Vena cava inferior 224, 234, 236

!!,all (pelvic) White matter

242, 243, 252 6, 10

~anthogranulomatous pyelonephritis

!.oom 104

261

215

Springer-Verlag Berlin Heidelberg New York

Computerized Axial Tomography An Anatomic Atlas of Serial Sections of the Human Body Anatomy - Radiology - Scanner By 1. Gambarelli; G. Guerinel; L. Chevrot; M. Mattei. 550 figures, VI, 286 pages. 1977 Cloth DM 240,-; US $ 105.60 ISBN 3-540-07961-0 (Also available in German)

Cranial Computerized Tomography Proceedings ofthe Symposium Munich, June 10-12, 1976 Editors: W.Lank~ch; E.Kazner. Editorial Board: T. Grumme; F. Marguth; HR.Mliller; H. Steinhoff; S. Wende. 620 figures, XIV, 478 pages. 1976 DM 78,-; US $ 34.40 ISBN 3-540-07938-6 Distribution rights for Japan: Nankodo Co. Ltd., Tokyo

The First European Seminar on Computerised Axial Tomography in Clinical Practice Editors: G.H.Du Boulay; LF.Moseley 335 figures, XI, 430 pages. 1977 DM 78,-; US $ 34.40 ISBN 3-540-08116-X Distribution rights for Japan: Nankodo Co. Ltd. Tokyo

AS. Takahashi

An Atlas . of Axial Transverse Tomography and Its Clinical Application 576 figures, VII, 329 pages. 1969 Cloth DM 216,-; US $ 95.10 ISBN 3-540-04730-1

Springer-Verlag Berlin Heidelberg New York

A Wackenheim

Roentgen Diagnosis of the Craniovertebral Region 500 figures, XXII, 601 pages. 1974 Cloth DM 403,-; US $177.40 ISBN 3-540-06615-2 Distribution rights for Japan: Igaku Shoin Ltd. Tokyo, Japan

A Wackenheim, IP.Braun

Angiography of the Mesencephalon Normal and Pathological Findings. 128 figures, XI, 154 pages. 1970 Cloth DM 144,-; US $ 63.40 ISBN 3-540-05266-6

S. Wende, E. Zieler, N. Nakayama

Cerebral Magnification Angiography Physical Basis and Clinical Results. With the collaboration ofK Schindler. 141 figures, VII, 150 pages. 1974 Cloth DM 163,-; US $ 71.80 ISBN 3-540-06651-9 Distribution rights for Japan: Igaku Shoin Ltd. Tokyo, Japan

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