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odd M. Blodgett, MD, Barry M. McCook, MD, and Michael P. Federle, MD

Combined positron emission tomography/computed tomography (PET/CT) became FDA-approved for clinical use in late 2001. There are several design advantages of combinedPET/CT over PET and CT acquired on separate devices, including more accurate CT andPET data co-registration, improved lesion localization, consolidation of imaging studies,and reduced scan times compared to dedicated PET. There are several protocols that canused to scan patients on combined PET/CT devices. Although there is no single “correct”protocol for performing a PET/CT scan, the use of oral and intravenous contrast media mayimprove the diagnostic value of the CT component. Whether to utilize contrast mediadepends on important clinical variables, including the specific type of tumor and thelikelihood of encountering viable abdominal and pelvic malignancy. This article discussesvarious protocols pertinent to PET/CT imaging, including how the CT portion of a PET/CTscan can be performed and optimized, as well as PET/CT interpretation and reportingissues.Semin Nucl Med 36:157-168 © 2006 Elsevier Inc. All rights reserved.

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ombined positron emission tomography/computed to-mography (PET/CT) has been in clinical use for nearly 5

ears after its development and initial evaluation at the Uni-ersity of Pittsburgh from 1998 to 2001.1-5 Advantages ofombined PET/CT over PET and CT acquired on separateevices include more accurate CT and PET data coregistra-ion (Fig. 1), improved lesion localization, consolidation ofmaging studies, and reduced scan times compared with ded-cated PET. In addition, the PET/CT gantry opening has aarge enough design to accommodate a flat pallet for radia-ion therapy planning purposes, potentially offering moreccurate assessment of tumor volume.

There have been many technological developments since therototype PET/CT scanner, with newer-generation PET/CTcanners using 2- to 64-slice (detector-row) CT scanners andhigh-resolution” PET scanners with 4-mm lesion detectability.n commercial PET/CT scanners, the CT can be performed as a

tand-alone procedure, whereas typically the PET componentannot be used without first performing CT.

There are many CT and PET scan protocol decisions toonsider with PET/CT, as well as logistical and personnelssues that can affect interpretation and reporting. This article

epartment of Radiology, University of Pittsburgh Medical Center, Pitts-burgh, PA.

ddress reprint requests to Todd M. Blodgett, MD, UPMC Departmentof Radiology, 200 Lothrop Street, Pittsburgh, PA. 15213. E-mail:

[email protected]

001-2998/06/$-see front matter © 2006 Elsevier Inc. All rights reserved.oi:10.1053/j.semnuclmed.2005.12.004

ill discuss various protocols pertinent to PET/CT imaging,ncluding a discussion of how the CT portion of a PET/CTcan can be performed, as well as a discussion of PET/CTnterpretation and reporting issues.

tandard PET/CT Protocolne of the major benefits of combined PET/CT is the ability

o acquire accurately coregistered PET and CT images in aingle imaging session. However, the general protocols forT are different with PET/CT because, unlike PET imaging,hich typically is a neck-through-pelvis survey of the body,T traditionally has been performed for regional evaluation

eg, head, neck, chest, abdomen, and pelvis). PET/CT imag-ng protocols therefore must be adjusted to adequately eval-ate the primary area of malignant involvement, as well as theost likely areas of tumor spread.For a typical “diagnostic” PET/CT scan using oral and intra-

enous (IV) contrast for the CT, patients generally are given oralontrast and injected with 18F-fluorodeoxyglucose (FDG) ap-roximately 1 hour before scanning. The patient subsequently isositioned in the PET/CT scanner and immobilized as indicatedfor instance, soft collars may be used to reduce neck movementn patients with head and neck cancer or lymphoma with necknvolvement). The first step in a standard PET/CT protocol gen-rally involves the acquisition of a digital scout radiograph, inhich the full patient is visualized and the area of interest is

elected (Fig. 2 [#1]). Patients then undergo the CT portion of

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he examination (Fig. 2 [#2]), followed by the PET portion of thexamination (Fig. 2 [#3]). A common misconception is that theT and PET data are acquired simultaneously; however, theata are acquired sequentially, with CT always performed first.ost scanners without a separate transmission rod source will

ot allow PET acquisition only but will allow dedicated CTcquisition. Because of the sequential data acquisition, there istill a high probability of CT and PET image misregistration if theatient moves between the CT and PET portions of the exami-ation (Fig. 3). Once attenuation correction (AC) and scatterorrection are performed using the attenuation coefficients fromhe corresponding CT portion of the scan (Fig. 2 [#4]), fusedccurately coregistered images are available for interpretationFig. 2 [#5]).

rotocol Optionsne important PET/CT protocol decision is whether IV con-

Figure 1 Inaccurate retrospective co-registration. This paa pericardiac mass identified on axial CT (arrow) (A). Tcorresponding PET images acquired on a different deinterpretation of the fused image in (B) was that the masa hardware-based combined PET/CT device, and an axipericardiac mass. The original coregistration misregistebiopsy showed a benign hamartoma, compatible with t

rast will be used and how and when it will be administered. t

here are different CT scan protocols for combined PET/CThat are performed in clinical practice today: (1) noncontrastith low current (�40 mAs used for AC and localizationnly) (Fig. 4A), (2) noncontrast with normal current (�140As), (3) normal current with IV and/or oral contrast (Fig.

B), or (4) both low-dose (for AC) and full-current (for diag-ostic interpretation) CT (Fig. 4C).6

ow-Dose Noncontrast CTerforming CT at a low-dose (�40-60 mAs) reduces theensitivity and specificity of the modality for detecting malig-ant lesions but usually is adequate for general anatomical

ocalization and is sufficient for performing PET AC. In thisethod, the CT replaces the typical transmission scan per-

ormed on dedicated PET scanners, significantly reducingcan times (as much as 40%) relative to dedicated PET. It alsorovides better anatomical localization compared with tradi-

as referred from an outside institution for evaluation ofwas subsequently retrospectively coregistered to axialgive the axial fused PET and CT image (B). Initial

alignant. A repeat PET/CT was performed at UPMC on/CT image (C) shows only minimal FDG activity in thediac FDG activity to the pericardiac mass. Subsequentings on the repeat PET/CT.

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PET/CT protocol issues and options 159

he lung (Fig. 5). Outpatient imaging centers without medi-al personnel that are available immediately or centers inhich the interpreting physician is trained in PET/nuclearedicine generally use this type of scanning algorithm. In

ddition to the decreased diagnostic sensitivity, additionalisadvantages of this type of approach include the presencef CT images that need to be interpreted but generally cannote billed for separately because of the poor quality of the

mages (Fig. 5). If clinically indicated, a separate diagnostic-uality CT may be performed as part of the PET/CT scanning

Figure 2 Standard PET/CT Protocol. A digital scout radiand the area of interest is selected (1). Patients then undeportion of the examination (3), Once attenuation correctcoefficients from the corresponding CT portion of the sinterpretation (5). (Figure courtesy of David W. Towns

Figure 3 Misregistration caused by patient movement. Man axial PET/CT image (C). This type of misregistration
CT acquisition (during the PET acquisition).
ession or as a separate CT performed on another CT scanner.owever, in addition to decreasing the accuracy of the coreg-

stration, using another device to acquire a diagnostic CTiminishes the advantage of imaging consolidation providedy PET/CT.

oncontrast CThis method uses a full-dose CT before performing the PETortion of the examination. This method might be performed

n patients with a significant contrast allergy or, perhaps, in

is first acquired, in which the full patient is visualizedCT portion of the examination (2), followed by the PET

d scatter correction are performed using the attenuation, fused, accurately coregistered images are available forniversity of Tennessee, Knoxville, TN.)

ration of axial CT (A) and PET (B) images are shown onto movement of the patient’s head to the right after the

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atients being evaluated for a single pulmonary nodule. TheT portion of the examination generally is interpreted and

eported, particularly in cases in which this is the desired CTmaging protocol.

ontrast-Enhanced CThe protocol that takes maximal advantage of the originalesign concepts of a state-of-the-art CT and PET in the sameevice is one that uses contrast-enhanced CT protocols forET/CT imaging. This method attempts to maximize the di-gnostic potential of the CT scan by using both oral and IVontrast before performing the PET portion of the examina-ion. Depending on the quality of the CT component, theET/CT scanner, these images may be comparable to theuality of a CT scan performed on a dedicated CT scanner.6-9

owever, factors including breathing artifacts and large scan-ing field of view can result in significant differences in theuality of the images.10

One important consideration for the use of IV contrast ishether there is appropriate medical coverage available to

espond to possible untoward contrast reactions. Also debatetill exists as to whether IV and/or oral contrast offer overlap-ing, purely complementary, or synergistic information,iven the added information offered by FDG on the PET partf the examination. Several studies have been published con-rming improved diagnostic accuracy of contrast-enhanced

igure 4 PET/CT protocols with and without IV contrast. Shown arecommonly used protocols in PET/CT imaging. (A) The first pro-

ocol uss the CT for attenuation correction and localization pur-oses; however, the CT is inferior quality to a CT scan performed at

ull dose with oral and IV contrast, as performed for the secondrotocol (B). The last protocol (C) uses the first low-dose CT forttenuation correction to avoid artifacts caused by contrast and useshe second full-dose contrast-enhanced CT for diagnostic purposes.

T compared with that of noncontrast CT for differentiating a

etween benign and malignant processes.11-35 Althoughany of these studies demonstrate a diagnostic improvement

f contrast over noncontrast CT, many also suggest that, forarious tumor types, using a multiphasic enhancement tech-ique may further improve the diagnostic capability of CT.alignancies with characteristic enhancement patterns, such

igure 5 Low-dose CT performed at 40 mAs. Select images from aT scan performed at 40 mAs show poor quality of the imagesbtained at this tube current with the exception of the lung. Thisethod generally provides more information in the thorax (A and B)

han in the neck and abdomen (C), where there is more tissue to
ttenuate the radiation beam from the CT.

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s hepatocellular carcinoma, which generally enhance (anday only be detectable) during the arterial phase, may be less

pparent on portal venous or delayed-phase images.11,16,31

onversely, cholangiocarcinomas may show delayed en-ancement, and optimization of the CT protocol for this in-ication includes performing a delayed-phase scan at ap-roximately 10 minutes. These types of protocols areossible with PET/CT, although they require more planningnd, in some cases, more time.

Because most oral and IV contrast agents have the potentialf generating artifacts on the AC PET images on most scan-ers, there are also protocol considerations when using con-rast agents for the CT portion of a PET/CT examination.hese artifacts, which are discussed in more depth in theubsequent sections, generally are easy to recognize and notsually clinically relevant. In addition, contrast agents renderessels and bowel distinct from other structures, helping tomprove reader confidence and specificity in differentiatingenign from malignant FDG uptake. Centers must, therefore,eigh the potential benefits of having a contrast-enhancedT with the disadvantages of AC artifacts on PET from usingontrast. At the University of Pittsburgh Medical Center, theverwhelming majority of CT scans performed as part of aET/CT are performed with oral and IV contrast.

ow-Dose CT Followedy Contrast-Enhanced CTne way to avoid CT AC artifacts caused by IV contrast is toerform a low-dose noncontrast CT that can be used for ACrst. Then, after the PET portion of the examination, a con-rast-enhanced CT can be performed for diagnostic purposes.owever, the disadvantage of this protocol is an increase in

he radiation exposure to the patient because they are under-oing 2 CT scans.36

rtifacts on PET/CTelated to CT Protocols

V Contrast AC Artifactss mentioned previously, one of the stated reservations about

he use of contrast media is that they may cause artifacts onhe AC PET images when using CT for AC.9,37-40 When denseontrast material is present in central venous structures dur-ng the CT acquisition, but not during the PET portion of thexamination, there tends to be an overcorrection of the PETata. This mismatch causes an area of linear artifact (mimick-

ng intense FDG accumulation) on the AC PET images (Fig.).41 Atypically, this artifact can appear focal and mimic aalignant lymph node in the axilla or supraclavicular area.40

onversely, a focus of FDG-avid tumor also could be ob-cured by the artifact.41 In addition, artifacts can have atypi-al appearances that can confound image interpretation asell. A relatively simple solution to diagnostic uncertainty

egarding the presence of a CT-based AC artifact is to inspecthe non-AC PET images, which should show no evidence ofDG activity. Unfortunately, it can be cumbersome to switch
etween the AC PET data and non-AC PET data using many a
ET/CT viewing systems, and some fusion viewing systemsill not allow side-by-side comparison of AC and non-ACET images. Alternatively, venous AC artifacts can be re-uced by using dual-head CT contrast injectors that uses aaline flush after the contrast bolus to decrease the amount ofontrast material in the central veins.

ral Contrast AC Artifactseveral oral contrast agents are available for clinical use iniagnostic imaging. In general, oral contrast agents should beiven no longer than 1 hour before scanning to maximize theotential that all small bowel loops are ideally opacified butvoiding the dense concentration of contrast within the colonhat occurs with longer delays. There are several differentypes of oral contrast media. Undiluted barium is not recom-ended for PET/CT because it will cause both streak artifacts

n the CT portion of the examination, as well as severe ACrtifacts on the PET portion of the examination. A standardilution of water soluble oral contrast such as GastroviewMallinckrodt Inc, Hazelwood, MO), using a 2% solution ofodium and meglumine diatrizoate will tend to cause someegree of AC artifact (Fig. 7), whereas contrast agents that are

ower in attenuation, such as Volumen (E-Z-EM Inc, West-ury, NY), generally do not.42-48 Most of the time, there isverlap of physiologic and artifactual bowel activity, and asong as the appearance of bowel activity is linear, it usually isot a source of concern. However, when the oral contrast ACrtifacts are more focal or irregular, they can be a diagnostichallenge. It is imperative to check the non-AC PET data inhese instances to be sure that a suspected lesion is not an ACrtifact.

Although some studies suggest that the use of oral contrastedia does not typically cause clinically significant AC arti-

acts,48 it has been reported by a different group that collec-ions of barium-based oral contrast material within the bowelo cause artifacts and overestimates of FDG activity in theowel by as much as 20%.48,49 The same group has proposed aegion-growing CT-based AC algorithm that appears to correctost, if not all CT-based AC artifacts. However, most PET/CT

canners to date do not use this alternative method of AC.It is still unclear to some interpreting physicians what the

dded clinical value of oral contrast is with PET/CT scanningiven the additional information that is obtained by havingDG from the PET portion of the examination. However,hen there is focal FDG uptake representing a possible met-

static lesion, it is helpful to have improved contrast of struc-ures offered by using IV and oral contrast, even if a lesionhows only subtle enhancement. Several benign processeslso have characteristic enhancement patterns that wouldtherwise be difficult to diagnose confidently without con-rast (Fig. 8).

It may be helpful to create contrast protocols based onndications, for instance, patients having tumors with a lowrevalence of abdominal metastases (eg, primary head andeck carcinoma) might be scanned without the use of oralontrast medium, whereas those with a greater likelihood of
bdomino-pelvic tumor would receive contrast.

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iaphragmatic Respiratory Artifactson-AC–based artifacts specific to PET/CT imaging alsoave been observed. Diaphragmatic motion during the CTcquisition can cause portions of the liver to appear displacednto the thorax (Fig. 9).10,50-52 Because CT typically is ac-uired with a breathhold at deep inspiration and PET typi-ally is acquired during tidal respiration, there is an inherentismatch in the diaphragmatic position during data acquisi-

ion that is most severe at a breathhold with deep inspiration.he magnitude of these diaphragmatic breathing artifacts isependent on how long it takes to acquire the data and onatient breathing instructions. Therefore, with slower single-nd dual-slice CT scanners, this artifact is seen in as many as0% of patients when the CT data are acquired with tidalreathing,10,53 whereas there is significantly less diaphrag-atic artifact with 16-slice CT scanners. Another way to re-uce breathing artifacts is to use a modified breathing algo-ithm, as described by Beyer and coworkers,10 instructing theatient to maintain shallow tidal respiration until the CTetector is near the bottom of the thorax, at which time theatient is instructed to stop breathing wherever he or she is in

Figure 6 IV contrast AC artifact. (A) Coronal AC PET imavein (arrow) correlating to IV contrast within the right sPET image (B) shows no evidence of FDG activity, com

he respiratory cycle, until the detector has passed through l

he liver. Breathholding until the CT detectors are throughhe liver minimizes respiratory motion and thus reduces sub-equent diaphragmatic breathing artifacts.

These diaphragmatic artifacts are the most clinically signif-cant when there are lesions in the superior liver or in theower thorax, potentially causing a liver tumor to be mistakens a lung tumor, or vice versa (Fig. 10).54 Radiotherapy ap-lications are more difficult as well because of the mismatch

n the anatomical structures.

rm Positioningnlike dedicated CT, where short scan times allows for rou-

ine scanning with the arms kept out of the field of view, withET/CT the arms may often be kept in the field of view toinimize patient discomfort. When the arms are positioned

t the side of patients, there can be significant beam harden-ng and streak artifacts in the CT images (Fig. 11), which cane especially problematic when the artifact overlaps with therea of interest. One potential solution is to scan all patientsith arms raised, which reduces the potential for artifacts in

he chest and abdomen. In patients with head and neck ma-

s linear FDG activity in the area of the right subclavianian vein (C and D). However, inspection of the non-ACwith an AC artifact.

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xamination focused on the neck can be performed with therms down. Faster scanners make more patients able to tol-rate having arms raised above their head. Others have rec-mmended placing arms in pillows at various heights by theatient’s side.

eimbursement Issuesew PET/CT codes recently have been developed, including8,814 (limited area), 78,815 (skull base to mid-thighs), and8,816 (whole body). These are used for PET acquired on aET/CT scanner, and the charges/reimbursement are slightlyigher than for the dedicated PET codes 78,811, 78,812, and8,813, reflecting the increased capital cost to purchase the

Figure 7 Enteric contrast artifact caused by retained thickPET/CT images (C) show apparent intense FDG activitcolon. Inspection of the axial non-AC PET image (D) shtransverse colon (arrow) caused by physiologic activitimages is artifactual, introduced during the attenuation cconcentrated in the colon, especially if given too long b

ombined device. p

In general, diagnostic (contrast-enhanced in most in-tances) CT studies should not be performed unless medi-ally necessary and ordered by the referring physician. Forases in which a diagnostic CT is performed, The Centers foredicare and Medicaid Services (CMS) have designated a 59odifier to be used to charge for the CT portion of the ex-

mination in addition to using the appropriate PET/CT bill-ng code. For other third party payers, billing may still reverto the older diagnostic PET and CT codes when a diagnosticT is performed.

uggested ProtocolsET and PET/CT are covered by CMS and most third-party

m. Coronal PET (A), fused PET/CT (B), and axial fusedlating to high-attenuation contrast material within theat there is only minimal FDG activity in the proximalthe artifactual intense FDG uptake seen on the otheron process. Barium-based contrast agents become moree PET/CT examination.

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taging and restaging; however, it is not clear whether allatients require a diagnostic CT as part of their PET/CT ex-mination. At the University of Pittsburgh, we have at-empted to identify potential patient populations that mighte adequately evaluated by a low-dose CT as part of theET/CT in an attempt to optimize the appropriate use ofET/CT, as well as to decrease overall cost of the examina-

Figure 8 Corpus luteal cyst mimicking a left adnexal metaa primary cervical carcinoma (arrowhead), as well as inshow intense FDG activity within the cervical carcinomaThe contrast-enhanced CT shows the typical appearanceotherwise normal appearing ovary. Subsequent resectiorather than a metastatic lesion.

Figure 9 Diaphragmatic breathing artifact. Coronal CT (Asuperior liver to appear detached into the thorax becaus
the diaphragm is at different positions.
ion, without compromising patient care. One potentialroup of patients in whom a low-dose CT may be sufficient issymptomatic patients with successfully treated malignan-ies undergoing surveillance imaging and in whom the over-ll index of suspicion for viable tumor is low. For example,atients with lymphoma often respond well to therapy witheduced tumor size and decrease in metabolic activity but

(A) On coronal PET, abnormal uptake is present withinadnexa (arrow). Axial CT and fused PET/CT (B and C)heads) and less FDG uptake in the left ovary (arrows).rpus luteal cyst with a thick rind of enhancement in an

e left ovary confirmed a hemorrhagic corpus luteal cyst

(B), and fused PET/CT (C) images show a portion of theeat sampling of the same area by the CT detector when

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eed to be evaluated several times per year for several yearsecause this is the period of highest risk for recurrence. Givenlow index of suspicion for viable tumor, a low-dose CTight be used for the PET/CT to reduce the radiation dose

nd overall cost of the procedures. However, any patient thats suspected of having active disease, regardless of his pri-

ary malignancy, is optimally evaluated with a diagnosticontrast-enhanced CT.

Another group of patients that may be sufficiently evalu-ted with a low-dose CT are patients who are being evaluatedor a solitary pulmonary nodule and who have had a good-uality CT scan performed recently (generally no longer than-4 weeks). It is likely that a contrast-enhanced or full-doseoncontrast CT would offer little additional information inhis subgroup of patients. At our institution, these 2 patientopulations (surveillance of lymphoma in asymptomatic pa-

Figure 10 Bronchoalveolar cell carcinoma adjacent to diactivity in the lower chest (arrow). Inspection of the cmild-to-moderate FDG-avid lesion immediately adjacewith tidal respiration. Subsequent biopsy showed bronc

ients and solitary pulmonary nodule evaluation in patients s

ith a recent CT) make up approximately 35% of all patientscanned.

ho Should Interpret PET/CThe issue of who is qualified to interpret a PET/CT scan isontroversial and beyond the scope of this review. However,ertain observations warrant consideration. Physicians inter-reting imaging studies generally are held responsible forecognizing and reporting abnormalities that are present onhe images, even if the explicit reason for obtaining the studys outside the expertise of the interpreting physician. Forxample, orthopedic surgeons interpreting musculoskeletalagnetic resonance scans or cardiologists interpreting car-iac CT or chest radiographs have been found to be medico-

egally negligent for missing neoplastic lesions present on the

matic artifact. Coronal PET (A) shows an area of FDGCT (B) and PET/CT-fused images (C) shows a subtlediaphragmatic breathing artifact from CT acquisitionolar cell carcinoma.

aphragoronalnt to a

tudies performed. Although we are unaware that this prin-

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iple has yet been tested for PET/CT interpretation, it seemsikely that the interpreting physician would be held liable foresions evident on the CT portion of a PET/CT scan, even if aisclaimer is included stating that the CT was acquired forhe purposes of attenuation correction and localization,ather than for diagnostic purposes. If enough information isresent on a CT scan to make a diagnosis, it may be regardeds diagnostic by definition, regardless of whether it is of pooruality. Many tumors that are not FDG-avid will be evidentn CT but may be overlooked by an interpreting physiciannfamiliar with the wide range of appearances of tumors andenign masses on CT scans (Fig. 12). Similarly, one shouldot interpret the PET portion of the examination withouteing thoroughly familiar with the range of normal and arti-

Figure 11 Effect of arm positioning On CT image qualitywith arms positioned at the patient’s side, showing beincreased beam attenuation from the upper extremities. Cthe patient (C and D) shows resolution of the artifact in

actual FDG-avid “lesions” that may be encountered. e

The issue of proper training and credentials for physiciansnterpreting the PET and CT portions of the examination haseen addressed recently by a task force comprised of mem-ers of the American College of Radiology and Society ofuclear Medicine.55

uture Direction of CT Protocolsery few studies have been performed actually comparingoncontrast with contrast-enhanced PET/CT. Even fewertudies have addressed the issue of whether multiphasic en-ancement of the CT portion of a PET/CT offers any potentialenefit. However, a single phase of contrast enhancement forT may not be optimal or adequate in some settings. For

nal (A) and axial (B) CT images from a patient scannedrdening artifacts in posterior abdomen caused by thee same patient scanned with the arms positioned abovedomen but now shows it in the area of the neck.

. Coroam-haT of th

xample, some hepatic tumors are variably FDG–avid and are

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ell known to be reliably detected only on a particular phasef a contrast-enhanced CT scan. Hepatocellular carcinomaypically is detected optimally on only an “arterial-phase”ontrast-enhanced CT scan, whereas cholangiocarcinomasually is best seen on delayed enhanced CT. Neither arterialor delayed-phase images acquired routinely on PET/CT ex-minations; rather, the CT images are acquired during a sin-le phase of parenchymal enhancement, often referred to ashe “portal venous” phase. Although it is possible to do aoncontrast, portal venous phase and delayed CT, it is diffi-ult or impossible to obtain arterial and portal venous phasesf imaging with the same bolus injection of contrast during aET/CT examination. Because the software is designed torogress to the PET portion of the examination after a CT,ost commercially available PET/CT scanners cannot

uickly scan the patient during different phases of parenchy-al enhancement. If arterial and portal venous phases areesired for a particular patient, the only current alternative iso perform two bolus injections, one for arterial acquisitionnd the second for the portal venous phase of imaging. Moretudies are needed to determine which patients may benefitrom multiphase CT imaging in PET/CT.

onclusionhere is no single “correct” protocol for performing a PET/CTcan. Important variables to be considered include the spe-ific type of tumor and the likelihood of encountering viablebdominal and pelvic malignancy. The use of oral and intra-enous contrast media may improve the diagnostic value of

Figure 12 Renal cell carcinoma. Coronal PET (A) is normis a slight protrusion of the inferior pole left kidney (arimages (C) demonstrate an enhancing solid renal massactivity compatible with renal cell carcinoma (proven at

he CT component, but can give rise to artifacts that may

nterfere with interpretation. Artifacts can be minimized byttention to technique and the use of newer faster PET/CTevices.

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Positron Emission Tomography/Computed Tomography: Protocol