alternative mod ali ties of chest minal

8/9/2019 Alternative Mod Ali Ties of Chest Minal

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Alternative modalitiesof chest imaging


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Introduction

The radiology of 50 years ago was a primitive sciencecompared with the radiology of today.

Examinations consisted primarily of radiographs of thechest, bones, and gastrointestinal tract, although someearly neuroradiologic studies were performed.

Chest fluoroscopy was common. Radiographic examinations of the chest were likewise

unsophisticated by today's standards.

There were no image intensifiers, nuclear medicinestudies, ultrasonography, computed tomography, or

magnetic resonance studies. How far we have come!


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Imaging Modalities

A. Plain radiographs

B. Ultrasonography

C. CT (including high resolution)

D. MR E. Ventilation-perfusion Scintigraphy

F. Positron emission tomography (PET)

scanning

G. Pulmonary & Bronchial Arteriography


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Plain radiographs

o The chest x-ray, an invaluable first line investigation,is a source of information and an indispensablediagnostic tool in medicine.

o The careful examination of the chest radiographconstitutes an essential component in themanagement of a number of different diseases.

o It is also used in emergency medicine and can

detect systemic diseases such as metabolic bonedisease and pulmonary metastases.


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How to take a proper Chest X-

ray


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Difference between PA and

AP viewsPA View

Spine and post ends of ribs

clearly seen

Ribs obliquely oriented Scapulae not overlapping the

thorax

Clavicles are horizontal

Normal sized cardiacsilhouette

AP ViewAP View

Not visualized clearlyNot visualized clearly

More horizontalMore horizontal

They do overlapThey do overlap

More obliqueMore oblique

EnlargedEnlarged


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PA VIEWAP V

IEW


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The lung fields are divided in three zones only for convenienceof the description of the lesion. However, they do notcorrespond to the anatomical lobes.

Upper zone: from apex to the lower border of the anterior endof second rib.

Middle zone: from the lower border of the second rib to the

lower border of the anterior end of fourth rib.

Lower zone: below the lower border of the anterior end offourth rib.


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o Each lung is dividedinto lobessurrounded bypleura.

o There are two lobeson the left , upper &lower, separated by

major fissure.

o Three on the right :upper, middle &lower, separated by

major fissure & minorfissure.


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Segmental anatomy of

the lung


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Limitations of Chest Radiography

o The chest x-ray is a very useful examination, but haslimitations.

o Some conditions of the chest will not show up on the

chest x-ray, so a normal chest x-ray doesn't necessarilyrule out all problems in the chest.

o For example, patients with asthma exacerbations canhave a normal chest x-ray. There are some cancers that

are too small or are difficult to visualize and may not beidentified. Pulmonary embolism cannot be seen on chestx-rays and require additional study.


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o A chest CT may be requested to further clarify a findingseen on the chest x-ray or to look for an abnormality notvisible on a chest x-ray .

o The degree of involvement of the lung, as well as thedistribution of disease, and anatomic location may bebetter evaluated with chest CT.

o Some diseases, such as chronic lung diseases, are

frequently evaluated with HRCT .


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US may be helpful in evaluation of persistent or unusual

areas of increased opacity in the peripheral lung, pleural

abnormalities, and mediastinal widening.

US is particularly useful in patients with complete

opacification of a hemithorax at radiography.

US allows characterization of pleural fluid collections as

simple, complicated, or fibro adhesive, which is important

information for planning thoracocentesis or thoracotomy.


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US allows easy distinction of pleural fluid from peripheralpulmonary infiltrates and also permits localization of

pleural fluid for aspiration.

At US, pleural fluid may be characterized as a simpleeffusion, a complicated effusion, or fibrothorax.

A simple effusion appears as clear anechoic or cloudyhypoechoic fluid with or without swirling particles .

A complicated effusion appears as septated ormultiloculated, hypoechoic fluid partitioned by fibrin

strands with no clear demarcation between the lung andpleural components .

Fibrothorax appears as a thickened, echogenic rind ofpleural plaque.


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Simple pleural effusion with floating debris. Chest radiographshows an ill-defined area of increased opacity in the left lower

lobe. Longitudinal US scan of the left lower lobe shows a large

amount of hypoechoic fluid containing swirling particles, an

appearance indicative of a simple effusion amenable to aspiration.

(SP) and an echogenic area of lower lobe consolidation (L).


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Complicated pleural

effusion with fibrin

bands. Transverse US

scan shows anechoicfluid containing mobile

echogenic bands. This

type of fluid collection is

amenable tothoracentesis.


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Intercostals oblique USscan shows thickening

of the visceral andparietal pleura (arrows).The pleural space isfilled with profuselyseptated fluid, which

has a honeycombappearance. This typeof Complicated pleuraleffusion is not reallyamenable to

thoracentesis.


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US clearly demonstrates the diaphragm & differentiates

subpulmonic effusion from subphrenic abscess.

US often allows detection of associated lung or pleural

masses hidden by pleural effusion.

The patient with a completely opaque hemithorax is an

ideal candidate for differentiation of massive pleural

effusion from pleural or lung masses .


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Chest radiograph shows complete opacification of the righthemithorax. Longitudinal US scan shows a massivepleural effusion containing echogenic masses (M) s/opleural metastases in a 4 yr old child with wilms tumour.


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In cases of chest wall lesions, US may enable

localization of the site of origin to soft tissues or anextrapleural intrathoracic location .

US may aid in diagnosis by allowing localization of

the lesion and characterization of it as cystic or solid.

Osseous involvement, particularly rib involvement, is

easily evaluated with US.


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An important feature of diagnostic ultrasound is its

apparent safety, so it can be used in children &pregnant females without concern for injury.

Patients readily accept an ultrasound examination

because the procedure requires only slight pressure onthe skin & minimal preparation.

Mobile ultrasound systems that can be taken to the

bedside, to intensive care & into the operating room arewidely used.


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Mediastinal US may have a screening role in the

evaluation of mediastinal masses somewhere

between the role of chest radiography and those of

the more expensive imaging techniques .

It is still uncommon to use US in the mediastinum.


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Chest radiography allows localization of masses

into the anterior, middle, or posterior mediastinum,

whereas US allows characterization of masses as

solid or fluid filled and detection of calcifications.

Both modalities are thus valuable in arriving at themost likely diagnosis.


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Chest radiograph shows a well-defined mass. The questionwas whether the mass was in the lung or the mediastinum.Subtle thoracic scoliosis is seen. Transverse US scanshows a fluid-filled cyst attached to a vertebra (V). On thebasis of the location and cystic nature of the lesion, adiagnosis of posterior mediastinal enteric or neurenteric cyst

was suggested.


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However, US may permit rapid clarification of

radiographically equivocal findings.

It may also partially replace CT and MR imaging in

certain situations, for example, in young children with

widening of the superior mediastinum to differentiatenormal thymus from mediastinal masses and in

critically ill patients in intensive care units.


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The normal thymus sometimes has a confusingappearance on plain chest radiographs.

Commonly encountered problems are a normal but

prominent thymus mimicking a mediastinal mass or upperlobe pneumonia or atelectasis .

Under these circumstances, US allows easy identification

of the normal thymus, thus enabling unnecessary furtherinvestigations to be avoided .


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Technologic improvements in transducers as well ascolor flow imaging have made chest US even moreuseful by revealing the morphology of pulmonary,pleural, and mediastinal structures in more detail.

Color flow imaging may be helpful in characterizing thelesion by demonstrating the vascularity and flow patternand in searching for anomalous vessels, such as occurin pulmonary sequestration.


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US is an effective, easily performed complement tochest radiography in the evaluation of puzzling areas of

increased opacity in the chest.

US may provide useful information that eliminates theneed for more invasive or expensive studies.


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Identification of air bronchograms and fluid

bronchograms at US and pulmonary vessels at color

flow imaging is useful in differentiating pulmonary

consolidation from lung masses and pleural lesions,

which are the main causes of puzzling areas of

increased opacity on chest radiographs.


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For evaluation of chest wall lesions, CT or MR

imaging is ultimately required. However, initial US

screening to determine whether the lesion is solid or

fluid filled and whether an underlying rib abnormality

is present may help limit the differential diagnosis.


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Sonography has become the imaging modality ofchoice for guidance of many interventional

procedures in the pleural space.

Following invasive procedures can be done underUSG guidance

~ diagnostic thoracentesis~ therapeutic thoracentesis

~ catheter drainage of pleural effusion

~ sclerosis of pleural space

~ pleural biopsy.


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The incidence of pneumothorax is 18% for clinically

guided thoracentesis 3% for sonographically

guided thoracentesis.


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CT evaluation of lung

pathology

Chest radiography remains the primary technique fordetecting most parenchymal & pleural abnormalities.

Both pleural and pulmonary parenchymal processes can

cause opacification that cannot be discriminated orcompletely characterized on standard chestradiographs.

Computed tomography can be helpful in confirming thepresence and extent of a lesion, and also may behelpful in characterizing the abnormality.


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The indications for CT are.

- Further evaluation of an abnormality identified on chestradiography.

- Assessment of patients with clinical suspected pulmonarydisease who have a normal or near-normal chest x-ray.

- Investigation of suspected airway abnormalities.

- Staging of lung cancer.- Evaluation of thoracic trauma.

- Evaluation of thoracic manifestation of known extra-thoracic diseases, especially metastasis.

- Guidance for biopsy & drainage procedures.


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With CT, the distinction between pleural andparenchymal processes, such as

a peripheral lung abscess versus empyema,

or a peripheral pulmonary nodule versus localizedpleural thickening,

and assessment of the relative amounts of

consolidation and pleural effusion, can be made.

Concomitant disease, involving more than onecompartment, such as bronchogenic carcinomadirectly invading the pleura & ribs can be assessed.


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Important clues can be made with the help of CT

imaging are.

the fat content of lipomas,

calcifications,

and extrapleural fat thickening in asbestos-related

pleural disease,

water density of loculated effusions


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The CT features useful in localizing a lesion to the pleura

are similar to those employed when evaluating chest

radiographs and include:

(i) a lenticular or crescent shape;

(ii) an obtuse or tapering angle at the chest wall

interface; and

(iii) a well-defined margin with the adjacent lung.


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Extrapleural lesions may have an associated

extrapleural soft-tissue mass,

bone destruction, or displaced extrapleural fat can help confirm the site of

origin.


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The routine administration of intravenous contrast mediahelps to differentiate atelectasis and consolidation, which

usually demonstrate marked enhancement, fromunenhancing pleural fluid.

Pleural malignancy and metastases usually enhance.

may be helpful in delineating areas of necrosis andidentifying peripheral enhancement of abscesses andempyemas.

The demonstration of pulmonary vessels within a lesionunequivocally identifies it as parenchymal.


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Computed tomography also may be valuable incharacterizing confusing paramediastinal air collections

as well as in distinguishing a medial pneumothorax froma pneumomediastinum or a parenchymal pneumatocele.

It may confirm a coexistent pneumothorax whenextensive subcutaneous air obscures findings on chestradiographs.

CT is useful in differentiating a large bulla from apneumothorax suspected on a conventional radiograph


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Computed tomography is more sensitive than

conventional radiography in demonstrating focal pleural

plaques, especially in depicting involvement of the

mediastinal and paravertebral pleura.


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Extensively calcified pleural plaques are seen involving

the posterior paraspinal pleura & pleura along the

diaphragmatic surface.


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Although oblique radiographs increase the sensitivity for

detecting pleural plaques, large calcified plaques can

simulate parenchymal disease and present a confusing

appearance on chest radiographs.

CT can clearly demonstrate the extent and

characteristics of the pleural disease and reveal the true

nature of obscured or simulated lung disease.


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CT demonstrates the anatomy of the mediastinum

very well; & thereby is very helpful in evaluation ofthe pathologies as well.

CT shows the mediastinal structures in the cross-

sectional view, & thereby eliminates the confusion

produced by the overlapping, as occurs in the

conventional chest radiograph.


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CT is the imaging modality of choice in the

assessment of the patient with clinical or radiographic

findings s/o aortic injury, thoracic spine fracture ordiaphragmatic tear f/b blunt chest trauma.

CT has overall greater sensitivity then radiography in

c/o pulmonary laceration, contusion, tracheobronchial injury.

CT provides optimal visualization of thoracic spine

fracture, sternal fracture and diaphragmatic injury.


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Spiral or helical CT scanning & electron beam ultrafast

CT scanning has altered several of the CT scanningprotocols traditionally used for examining the thorax.

Advantages ofspiral CT scanning are

- rapid scan in one or two breath holds- reduction in volume of contrast needed for optimal

opacification of vessels

- the potential for multi-planar or three-dimensional

reconstructions.


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HIGH RESOLUTION

COMPUTED

TOMOGRAPHY (HRCT) Plain x-ray chest-is indispensable and remains the

screening modality of choice in patients with

suspected diffuse lung disease.

10-15% of diffuse lung diseases, 30-50% of

bronchiectasis and 20-60% of patients with

emphysema will have a normal chest x-ray normal.


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Large part of the lung is obscured by the mediastinum

and diaphragm.

X-ray seldom allows a confident specific diagnosis.

X-ray findings seldom correlate with the functional,

pathological and clinical impairment.

Interobserver variation


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A NEW LOOK AT A PATTERN

RECOGNIZATION OF DIFFUSE

LUNG DISEASE The common practice of describing the histologic

distribution of pulmonary lesions from their radiographicpatterns is often inaccurate.

Thus chest radiographs are limited in their ability tocharacterize lung morphology precisely and to representthe pathological alteration in morphology that occurs inthe presence of lung disease.


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High-resolution CT (HRCT) is currently the most

accurate noninvasive tool for evaluation of lung structure

AND diffuse lung disease.

clarity and precision

Detection and characterization

Confidence


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INDICATIONS FOR HRCT

I dont know pattern on radiograph

Abnormal PFT/Clinically diffuse lung disease withnormal radiograph

X-ray findings not correlate with the clinical picture

To monitor the activity of a disease and response totreatment

Prior to taking a lung biopsy

To determine the reversibility of the disease

Metastatic disease?


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HRCT is indispensible part of work-up of a patient

with suspected diffuse lung disease.

In view of clinical background and laboratory

investigation- the most appropriate diagnosis can be

reached with reasonable confidence.


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Magnetic resonance imaging

MRI is no substitute for CT in the investigation of

most thoracic conditions that require cross-sectional

imaging.

There are few specific instances in which MRI is

useful problem solving technique.

There is increasing interest in the role of MR

angioraphy for the diagnosis pulmonary embolism.


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MRI can identify cystic mediastinal lesions such asbronchogenic cysts that may appear solid on CT scans.

In lung cancer staging, MRI has only a secondaryproblem solving role where CT is inconclusive or in whomcontrast media injection is contraindicated.

MRI may also be helpful in the assessment of lesionslocalized to the diaphragm


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In patients with lymphoma, MRI has no advantage over

CT in staging, but it may be useful in patient follow-up. In

patients treated for lymphoma, MRI is highly

recommended for those having a residual mass to

attempt a distinction between active tumour and inactive

fibrous residual soft tissue.

MRI is also useful for detecting recurrence of lymphoma

in the chest wall.


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The ideal MRI technique should include cardiac gating

and presaturation studies of incoming blood, fatsuppression techniques and combined interpretation ofboth T1- and T2-weighted images.

Intravenous injection of gadolinium may be required.

alternative mod ali ties of chest minal

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