best practice: implementation and use of abdominal dual-energy ct in routine patient care

AJR:199, November 2012 S71

with abdominal imaging using a dual-source DECT scanner with discussion of single-source DECT implementation.

Scanning WorkflowWhen the patient presents to the imaging

department, a knowledgeable technologist must be able to decide whether DECT is pos-sible. This is most critical with dual- source DECT systems in which the reconstruction FOV of the high-energy tube is limited to 33 cm. However, with careful positioning, most patients can be examined this way be-cause the relevant anatomic features will be incorporated into the reconstruction FOV, and the subcutaneous fat will be excluded (Fig. 1). The increased coverage of the low-energy tube from 26 to 33 cm has been a major factor in the wider applicability of du-al-source DECT. Because we use dose mod-ulation (CARE Dose4D, Siemens Health-care), patient centering is critical for proper functioning [2]. Automatic dose modulation is currently not available for single-source DECT systems.

For dual-source DECT we use 80 kV as the routine low-energy setting, reserving the 100-kV setting for patients who weigh more than 220–300 pounds (100–136 kg). We pre-fer 80 kV as the lower energy because it im-parts greater contrast to the blended images. A knowledgeable technologist looks at the distribution of the body weight and the to-tal weight. On single-source DECT systems, dual energy is currently limited to patients

Best Practice: Implementation and Use of Abdominal Dual-Energy CT in Routine Patient Care

Alec J. Megibow1

Dushyant Sahani2

Megibow AJ, Sahani D

1Department of Radiology, NYU Langone Medical Center, 550 First Ave, Rm HCC 232, New York, NY 10016. Address correspondence to A. J. Megibow ([email protected]).

2Department of Radiology, Harvard Medical School, Massachusetts General Hospital, Boston, MA

Dual - Energ y CT • Cl in ica l Perspect ive

AJR 2012; 199:S71–S77

0361–803X/12/1995–S71

© American Roentgen Ray Society

he value of obtaining chemi-cal composition and density in-formation from CT studies per-formed at different energies

was first reported in 1977 [1]. However, the ability to acquire this information with dual- energy CT (DECT), also referred to as spectral imaging, has become a clinical re-ality only within the last 6 years. Two com-mercially available system designs are in current clinical use: a single-source rap-id kilovoltage- switching dual-energy scan-ner (HD750, GE Healthcare), referred to as single-source DECT, and a dual-source du-al-energy scanner (Definition FLASH, Sie-mens Healthcare), referred to as dual-source DECT. The technical aspects of these scan-ners are described in detail elsewhere in this issue. In both technologies, image data are collected at two different energies: 140/80 kVp for single-source DECT and 140/80 or 100 kVp for dual-energy DECT. Because the same object has different attenuation values (Hounsfield units [HU]) at different voltages (kilovolts), objects can be classified by both traditional attenuation and chemical compo-sition, the latter information the direct result of data from the two energies. The conse-quences of this enhanced CT capability have resulted in an ever widening array of clinical applications detailed elsewhere in this issue. The purpose of this perspective is to docu-ment our experience with adopting DECT as a routine clinical imaging method. Clini-cal examples are drawn from our experience

Keywords: dual-energy CT, IV contrast, radiation, workflow

DOI:10.2214/AJR.12.9074

Received April 12, 2012; accepted after revision April 19, 2012.

Publication of this supplement to the American Journal of Roentgenology is made possible by a grant from Siemens Healthcare.

T

OBJECTIVE. The purpose of this perspective is to document an experience with the adoption of dual-energy CT (DECT) for routine clinical imaging.

CONCLUSION. Successful implementation of DECT requires that technologists un-derstand standards of image quality, be empowered to select appropriate patients, and under-stand networks for image routing. Radiologists need minimal facility with workstations to access the information embedded in DECT. DECT can be performed at a reduced effective radiation dose compared with single-energy CT and with lower doses of IV contrast material.

Megibow and SahaniAbdominal Dual-Energy CT

Dual-Energy CT Clinical Perspective

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Megibow and Sahani

who weigh less than 260 pounds (118 kg). Clinical indication–specific use of DECT is another approach practiced at few institu-tions. Although the bore of a single-source DECT scanner is wider (50 cm), the low-energy acquisition is restricted to 80 kV. Therefore, image noise may limit the ability to maintain image quality for larger patients unless scanning is performed at slower tube rotation. In the use of dose modulation soft-ware on dual-source DECT scanners, pa-tient centering is critical for proper dose reduction [2]. In addition, the dual-source DECT systems have dual energy–specific noise reduction variants so that either iter-ative reconstruction in image space (IRIS, Siemens Healthcare) or sinogram-affirmed iterative reconstruction (SAFIRE, Siemens Healthcare) can be used to facilitate radia-tion dose reduction. Automatic dose modu-lation and iterative techniques are current-ly not available for dual-energy scanning and image reconstruction on single-source DECT systems.

Both systems are MDCT scanners equipped with the ability to acquire images with isotro-pic voxels that allow full 3D capability once the final images are reconstructed. The tech-nologist must consider technical parameters that will maintain departmental standards of image quality. For dual-source DECT scan-ning, we acquire images with a 0.6-mm de-tector configuration that generates images with minimum 0.75-mm isotropic voxels or with a 1.2-mm detector configuration that generates images with a minimal 1.5-mm isotropic voxel. We defer to the narrow de-tector configuration as our routine, reserving

the wider detector for long z-axis acquisi-tions, such as CT angiography, and for mul-tiple acquisition studies of patients younger than 40 years, in which the wider detector allows maintenance of image noise at lower milliamperage settings. When a dual- source system is used, the detector configurations are identical for both tubes.

In summary, technologists play key roles in determining whether a patient can be appropriately imaged with DECT. Exact positioning is critical to encompassing rel-evant anatomy in the reconstruction field and for proper functioning of dose modula-tion on dual-source DECT systems. DECT studies can then be performed according to the institutional protocols used for single-energy CT studies.

Reconstruction WorkflowThe acquired high- and low-energy im-

ages are segregated into two separate streams of data. Single-source DECT sys-tems acquire approximately 1000 140-kVp projections and 1000 80-kVp projections. Images with a 512 × 512 matrix are recon-structed from the raw data in the projection space. Dual-source DECT systems recon-struct individual images from the 140- and 80/100-kVp beams. These images can be viewed as separate sets or blended into an image that simulates a conventional single-energy CT image [3].

Each dual-energy acquisition from a dual-source DECT system generates three separate sets of images: 140-kV images, 80-kV imag-es, and a mixed or blended dataset. The radi-ologist chooses the ratio of 80- and 140-kV

images to produce this image set. The goal is to create images that will have an overall ap-pearance simulating a traditional single- energy CT image. In general, 140-kV images have less noise and less inherent contrast, whereas 80-kV images have more contrast and more image noise. The default ratio is a 50% con-tribution from each of the high and low ener-gies. In our practice, when we acquire images using 140/80 kVp, we use a 60% contribu-tion from the 140-kV images and 40% from the 80-kV images. Conversely, when using 140/100 kVp, we use a 60% contribution of the 100-kV image and 40% of the 140-kV im-age. These blending ratios are determined ac-cording to the preference of the radiologists in the practice and are set up when the sys-tem first comes online. Once these settings are established, they are not altered on a case-by-case basis by either the technologist or the protocoling radiologist (Fig. 2).

The low- and high-energy images can also be blended to maximize high- and low-contrast elements. Traditional image blend-ing (irrespective of the ratio of contribu-tions from the 140- and 80-kV images) can be thought of as a continuous linear function with equal weighting of the noise character-istics of the high-energy scan and the con-trast characteristics of the low-energy scan. Nonlinear blending (modified sigmoid blend-ing), which highlights the lowest attenuation structures within the image (based on HU), produces images that accentuate the bright-est pixels but not increasing image noise [4].

With a single-source DECT system, four sep-arate sets of images are typically generated on the scanner console: From the high-ener-

A

Fig. 1—74-year-old man with history of enlarged prostate. Example of technologist role in positioning.A, Localizer image reveals obese habitus.B, CT scan shows careful positioning by technologist can assure that relevant anatomic structures are contained in dual-energy reconstruction circle, borders of which are marked by arrowheads.

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Abdominal Dual-Energy CT

gy (140 kVp) and low-energy (80 kVp) data, a 140-kVp image series is generated that resem-bles a traditional CT image series, and a mate-rial density pair series of low- attenuating (water) and high-attenuating (iodine) materials is creat-ed. The DECT image data can be processed to obtain images at any desired single-photon en-ergy (monochromatic/monoenergetic) level be-tween 40 and 140 keV to enhance contrast dif-ferences between two adjacent structures. The monochromatic rendering simulates the image appearance as if it were created from an x-ray source that produced only photons at a single energy. Because monochromatic DECT im-ages are generated from projection-space data, they are less affected by beam-hardening artifact and provide more accurate CT numbers than do single- energy CT images. Images generated at a photon energy level of 60–77 keV have been re-ported to have an optimal peak contrast-to-noise ratio. From dual-energy data, an effective atom-ic number (Zeff), which is a descriptor of densi-ty and the atomic number of a material, can also be derived that can used to differentiate materi-als. However, this process requires a vendor- provided workstation for image processing. With dual-source DECT, the low-energy images can be viewed as an individual dataset.

Image RoutingBecause each acquisition results in a min-

imum of three image datasets, the total re-construction time for a DECT study is longer than for a single-energy study. For instance, an otherwise routine abdominopelvic CT scan obtained with 0.6-mm detector configu-ration and reconstructed at 0.75 mm will con-tain on the order of 800 individual images with single-energy CT inflated to 2400 thin-section images for dual-source DECT. This

is exacerbated when a multiple-acquisition protocol is used. Even at the reconstruction speed of today’s CT systems—approaching 20 images per second—there is still a recon-struction time penalty related to DECT ac-quisition. Using noise reduction procedures (e.g., adaptive statistical iterative reconstruc-tion [ASIR] on GE Healthcare scanners and IRIS on Siemens Healthcare scanners) adds reconstruction time per image. Radiologists who choose to implement a DECT program need to be thoughtful about how the large numbers of images are moved within the radiology department. In our practice, we send all three datasets to both a standalone workstation (Leonardo MMWP, Siemens Healthcare) and a thin-client server (Syngo-Via, Siemens Healthcare), both of which are equipped with DECT image-processing ca-pabilities. We do not send these images to the PACS or use them for routine viewing; rath-er, they remain available in the MMWP da-tabase or thin-client server and removed as the hard drives become progressively filled. They are contemporaneously available for image processing, as described later (see Im-age Viewing). Once again, the importance of knowledgeable technologists who under-stand the departmental network cannot be overemphasized. The technologist must map the image sets sent to the thin-client worksta-tion so that preliminary dual-energy calcula-tions can be performed in the background.

Image ViewingOnce the image-blending method is chosen,

the workflow described up to this point can result in diagnostic-quality images that can be viewed the same way as single-energy CT data. As they do for single-energy CT studies,

our technologists acquire thin-section images to create thick-section (4-mm axial, 3-mm coronal) images and send them to the PACS, from which they can be viewed as convention-al CT images. These thick-section images are created from the mixed or blended dataset, au-tomatically generated from the dual-energy acquisition. With single-source DECT, 140-kV images are first reconstructed at the scan-ner console. If there is no specific need for ad-ditional dual-energy data, the 80-kV images are not reconstructed; rather the monochro-matic/monoenergetic simulated low-voltage images can be viewed. If additional process-ing is required (e.g., renal mass characteriza-tion), images are aligned to create material basis pairs [5].

The ability to perform material decom-position is the major benefit of DECT. This process allows a specific component (e.g., iodine, calcium, water) of the image to be selected and then either highlighted (iodine map) or removed (virtual unenhanced im-age). The dual-source DECT systems use a three-material decomposition algorithm that provides actual attenuation measure-ments in HU that can be analyzed exactly as on conventional single-energy CT imag-es [6, 7]. To view these images, we use the thin-client server model. This tool can be launched directly from the PACS (note that our PACS vendor is different from the thin-client vendor), the images appearing side by side with the traditional PACS images. The display is configurable; in our practice we view linear blended, optimally blended, 80-kV, and virtual unenhanced images simulta-neously (Fig. 3). Additional processing can generate a variety of image types, including iodine maps for quantitative image analysis,

Fig. 2—52-year-old man referred for abdominal pain. Appearance of dual-energy CT images changes depending on how radiology practice blends low-noise, low-contrast images from 140-kVp tube with higher-noise, higher-contrast 80-kVp images to simulate familiar 120-kV images. Radiologists settle on blending ratios during initial application setup.A, 70% 140 kV, 30% 80 kV.B, 50% 140 kV, 50% 80 kV.C, 30% 140 kV, 70% 80 kV.

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bone-removed images for CT angiographic studies, and renal stone content analytic im-ages, to name a few examples. Virtual unen-hanced images can alternatively be created by the radiologist and exported to the PACS or by the technologist at the time of the scan. This workflow saves technologist time and reconstruction time at the console but re-quires the radiologist to be familiar with the thin-client user interface. Individual key im-ages viewed on the workstation or thin client (e.g., a comparison of attenuation in HU be-tween enhanced and virtual unenhanced im-ages) can be exported to the PACS. Current-ly, more applications specific to dual energy are available with the standalone Leonardo MMWP workstation than with the current thin-client software release. These addi-tional functions include monochromatic im-aging, gout imaging, and pulmonary blood flow analysis, to name a few.

For users of single-source DECT, a two-material decomposition algorithm creates material-density images. These are displayed as basis material pairs, such as iodine and wa-ter pairs. From this basis pair, a set of iodine-density images and water-density images can be generated [5]. As described earlier, the low-voltage single-source DECT images cannot be directly displayed. This limitation is over-come by the ability to create monochromatic/monoenergetic images at kiloelectron volt val-ues that simulate the 80-kV spectrum (Fig. 3). Attenuation values in HU cannot currently be directly measured from these images; rather the concentration of iodine in milligrams per milliliter can be displayed (Fig. 4). However, the chemical information can be displayed as a color-coded map that shows, for instance, the presence or absence of iodine in a region on the image or as a graphical spectral attenu-ation curve [3].

Why Use Dual-Energy CT as a Routine Imaging Method?

Having a 6-year accumulation of experi-ence with DECT, we can begin to ask wheth-er this technology can be used as the rou-tine method of clinical CT. Although several niche applications (e.g., gout imaging, renal stone chemical analysis, iodine quantifica-tion in tumors) have clinical utility and re-search interest, these applications alone are not compelling reasons to purchase and im-plement a DECT program. However, sub-stantial advantages inherent in dual acquisi-tion that relate directly to patient safety have convinced us in our practice that our routine use of DECT is justified. The safety benefits of DECT relate directly to, first, improved iodine conspicuity, facilitating reduction of the volume of IV contrast material neces-sary for vascular and solid organ opacifica-tion and, second, reduction of radiation dose to the patient.

The ability to acquire images at low volt-age settings increases the chances for photo-electric interactions with substances with a K-edge near the mean energy of the beam. Iodine with its K-edge at 53 keV is ideally suited. The mean energy of the 80-kV beam delivered from a dual-source DECT system is 56 kV. This leads directly to brighter sig-nal intensity from iodine in vessels and in or-gan parenchyma. Low-voltage (≤ 100 kVp) imaging inherently delivers a lower patient dose and yields higher iodine signal [8, 9]. In dual-energy acquisitions, the low-voltage images are available as a routine part of the imaging study and therefore can be used to produce high-quality CT angiographic imag-es. The blending with the higher-voltage im-ages reduces noise on images viewed for di-agnostic purposes. A second consequence is the ability to reduce the total amount of io-dine given to a patient undergoing CT an-giography [10]. Using the ability to create monoenergetic simulations of 70-keV data from single-source DECT data improves the contrast-to-noise ratio compared with that of 120-kV images. This finding has been vali-dated in phantom studies [11] and in our clin-ical experience in evaluation of abdominal aortic aneurysm, in which an increase in in-travascular attenuation of 270% with 50-keV and 126% with 70-keV monoenergetic simu-lations was achieved over the attenuation on 120-kVp images. These results have led us to reduce the amount of iodine administered as much as 30%. The low-voltage imag-es derived directly from dual-source DECT

Fig. 3—60-year-old woman with lung carcinoma metastatic to liver. Example of dual-energy image display in our practice. Although blended images simulating single-energy 120-kV CT images can be viewed at PACS workstation in same manner as for traditional CT diagnosis, thin-client dual-energy interface allows simultaneous viewing of dual-energy data in presentation that allows radiologist to take full advantage of acquisition. User can configure interface to display images in any manner.A, Virtual unenhanced image.B, Linear-blended 140/80-kV image.C, Optimally blended 140/80-kV image.D, 80-kV image.

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and from monoenergetic simulations from sin-gle-source DECT acquisitions also provide in-creased contrast resolution of solid organs, in-creasing lesion-to-background differences and thereby increasing the conspicuity of patholog-ic changes in solid organs [3, 12, 13] (Fig. 4).

There are two ways in which use of DECT can decrease radiation dose: by eliminating un-necessary acquisitions and by inherent proper-ties of the dual-energy acquisition itself. Far and away the greatest benefit to patients will be elimination of acquisitions performed be-fore IV administration of contrast material. It is assumed that both the image quality and CT numbers obtained from virtual unenhanced im-ages are both acceptable and close enough to the values obtained from true unenhanced im-

ages. The quality of virtual unenhanced imag-es has substantially improved compared with images obtained with the earlier dual-source DECT scanners. The addition of tin filtration to the high-energy tube has resulted in virtu-al unenhanced images with 30% noise reduc-tion without affecting the blended contrast- enhanced images [14]. Results of several studies suggest that true unenhanced acquisi-tions can be eliminated in liver evaluation [15–17] and CT cholangiography [18]. Published studies have documented successful character-ization of adrenal [19, 20] and renal [21, 22] masses. We find this capability most useful in rapidly working up incidental masses that if detected with single-energy CT may require the patient to return for additional imaging.

With dual-source DECT systems, we have observed a consistently decreased volume CT dose index compared with that of single-energy CT. Comparing size-matched control patients and using an equal strength of dose modulation in both groups, we found the mean difference was 24% lower for DECT than for single-energy CT, although there was slightly higher image noise (Ng J, et al., presented at the 2012 annual meeting of the American Roentgen Ray Society). Use of it-erative reconstruction methods can suppress some of this increased noise and will contin-ue to improve image quality and acceptabil-ity. Combining the ability to acquire isotro-pic voxels at lower dose (allowing creation of 3D images and multiplanar reformats at

A B

C

Fig. 4—72-year-old man undergoing follow-up after abdominal aortic aneurysm repair. Dual-energy CT angiography was performed with 70 mL of iodinated contrast material (370 mg I/mL).A–C, Axial 140-kV image (A), dual-energy 50-keV monochromatic image (B), and dual-energy iodine map (C) show small endoleak (arrow) that is more conspicuous in B and C, owing to higher attenuation of iodine, than on 140-kV image.

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varying contrast blends) with, by the use of material decomposition, the ability to gener-ate virtual unenhanced images (eliminating extra acquisitions) can allow us to image at increasingly lower doses and preserve image quality (Fig. 5).

Several incompletely resolved issues cur-rently limit the widespread adoption of virtu-al unenhanced imaging to replace true unen-hanced acquisition. First, larger-scale studies are needed (and planned) to understand the reliability of CT numbers generated with virtual unenhanced imaging compared with true unenhanced imaging. Second, radiolo-gy practices need guidance on how to submit charges for this analysis. If an imaging ex-amination is requested as a CT study without and with IV contrast administration and the unenhanced portion is acquired from DECT data, it is not yet resolved how practices may bill for this service.

SummaryIn our practice, when only a dual-source

DECT scanner is available, every patient scheduled for an abdominopelvic CT study on that scanner is examined in the dual-energy

mode. When dual- and single-source DECT scanners are available, dual-energy scanning based on clinical indication is performed with single- and dual-source DECT. We ac-cept the minimally noisier images in the con-text of overall reduced patient radiation dose and reduced amount of iodinated contrast material. We believe that current research, both published and ongoing, will validate the elimination of true unenhanced acquisitions, substantially reducing patient radiation dose. Knowledgeable technologists are critical to assuring that individual patients can be ap-propriately examined with DECT and that patient throughput in a busy department can be maintained.

References 1. McDavid WD, Waggener RG, Dennis MJ, Sank

VJ, Payne WH. Estimation of chemical composi-

tion and density from computed tomography car-

ried out at a number of energies. Invest Radiol

1977; 12:189–194

2. van Straten M, Deak P, Shrimpton PC, Kalender

WA. The effect of angular and longitudinal tube

current modulations on the estimation of organ

and effective doses in x-ray computed tomogra-

phy. Med Phys 2009; 36:4881–4889

3. Silva AC, Morse BG, Hara AK, Paden RG, Hongo

N, Pavlicek W. Dual-energy (spectral) CT: appli-

cations in abdominal imaging. RadioGraphics

2011; 31:1031–1046; discussion 47–50

4. Holmes DR 3rd, Fletcher JG, Apel A, et al. Eval-

uation of non-linear blending in dual-energy

computed tomography. Eur J Radiol 2008;

68:409–413

5. Kaza RK, Platt JF, Cohan RH, Caoili EM, Al-

Hawary MM, Wasnik A. Dual-energy CT with

single- and dual-source scanners: current applica-

tions in evaluating the genitourinary tract. Radio-

Graphics 2012; 32:353–369

6. Johnson TR, Krauss B, Sedlmair M, et al. Mate-

rial differentiation by dual energy CT: initial ex-

perience. Eur Radiol 2007; 17:1510–1517

7. Primak AN, Ramirez Giraldo JC, Liu X, Yu L,

McCollough CH. Improved dual-energy material

discrimination for dual-source CT by means of

additional spectral filtration. Med Phys 2009;

36:1359–1369

8. Wintersperger B, Jakobs T, Herzog P, et al. Aorto-

iliac multidetector-row CT angiography with low

kV settings: improved vessel enhancement and

simultaneous reduction of radiation dose. Eur Ra-

diol 2005; 15:334–341

9. Kalva SP, Sahani DV, Hahn PF, Saini S. Using the

K-edge to improve contrast conspicuity and to

lower radiation dose with a 16-MDCT: a phantom

and human study. J Comput Assist Tomogr 2006;

30:391–397

10. Godoy MC, Naidich DP, Marchiori E, et al. Sin-

gle-acquisition dual-energy multidetector com-

puted tomography: analysis of vascular enhance-

ment and postprocessing techniques for evaluating

the thoracic aorta. J Comput Assist Tomogr 2010;

34:670–677

11. Matsumoto K, Jinzaki M, Tanami Y, Ueno A, Yamada

M, Kuribayashi S. Virtual monochromatic spec-

tral imaging with fast kilovoltage switching: im-

proved image quality as compared with that ob-

tained with conventional 120-kVp CT. Radiology

2011; 259:257–262

12. Macari M, Spieler B, Kim D, et al. Dual-source

dual-energy MDCT of pancreatic adenocarcino-

ma: initial observations with data generated at 80

kVp and at simulated weighted-average 120 kVp.

AJR 2010; 194:144; [web]W27–W32

13. Robinson E, Babb J, Chandarana H, Macari M.

Dual source dual energy MDCT: comparison of

80 kVp and weighted average 120 kVp data for

conspicuity of hypo-vascular liver metastases. In-

vest Radiol 2010; 45:413–418

14. Primak AN, Giraldo JC, Eusemann CD, et al.

Dual-source dual-energy CT with additional tin

filtration: dose and image quality evaluation in

phantoms and in vivo. AJR 2010; 195:1164–1174

Fig. 5—26-year-old woman referred for inability to empty bladder. Series of images from different portions of dataset of thin-client dual-source dual-energy CT urogram show that each dataset can be independently examined. Examination was performed in single acquisition in urographic phase. With combination of single dual-energy acquisition, dose modulation, and iterative reconstruction (SAFIRE), effective dose for this study was 2.97 mSv.A, Virtual unenhanced image.B, Maximum-intensity-projection urogram produced from linear blended 140/80-kV data.C, Optimal blended 140/80-kV image.D, 80-kV image.

Dow

nloa

ded

from

ww

w.a

jron

line.

org

by U

nive

rsity

of

Ari

zona

Hea

lth S

cien

ces

Lib

rary

on

05/0

6/13

fro

m I

P ad

dres

s 15

0.13

5.13

5.70

. Cop

yrig

ht A

RR

S. F

or p

erso

nal u

se o

nly;

all

righ

ts r

eser

ved



15. De Cecco CN, Buffa V, Fedeli S, et al. Dual en-

ergy CT (DECT) of the liver: conventional versus

virtual unenhanced images. Eur Radiol 2010;

20:2870–2875

16. Zhang LJ, Peng J, Wu SY, et al. Liver virtual non-

enhanced CT with dual-source, dual-energy CT:

a preliminary study. Eur Radiol 2010; 20:2257–

2264

17. Barrett T, Bowden DJ, Shaida N, et al. Virtual un-

enhanced second generation dual-source CT of

the liver: is it time to discard the conventional un-

enhanced phase? Eur J Radiol 2011 Apr 16 [Epub

ahead of print]

18. Sommer CM, Schwarzwaelder CB, Stiller W, et

al. Iodine removal in intravenous dual-energy CT-

cholangiography: is virtual non-enhanced imag-

ing effective to replace true non-enhanced imag-

ing? Eur J Radiol 2011; 81:692–629

19. Gnannt R, Fischer M, Goetti R, Karlo C, Leschka

S, Alkadhi H. Dual-energy CT for characteriza-

tion of the incidental adrenal mass: preliminary

observations. AJR 2012; 198:138–144

20. Ho LM, Marin D, Neville AM, et al. Character-

ization of adrenal nodules with dual-energy CT:

can virtual unenhanced attenuation values replace

true unenhanced attenuation values? AJR 2012;

198:840–845

21. Graser A, Johnson TR, Hecht EM, et al. Dual-

energy CT in patients suspected of having renal

masses: can virtual nonenhanced images replace

true nonenhanced images? Radiology 2009; 252:

433–440

22. Kaza RK, Caoili EM, Cohan RH, Platt JF. Distin-

guishing enhancing from nonenhancing renal le-

sions with fast kilovoltage-switching dual-energy

CT. AJR 2011; 197:1375–1381

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