Special Communication

C-arm Computed Tomography for HepaticInterventions: A Practical GuideAlessia Tognolini, MD, John Louie, MD, Gloria Hwang, MD, Lawrence Hofmann, MD, Daniel Sze, MD, PhD,

and Nishita Kothary, MD

With adoption of catheter-based techniques that require technically difficult catheterization, the need for imagingplatforms that exploit the advantages of multiple modalities and offer three-dimensional visualization has corre-spondingly increased. At the authors’ institution, C-arm computed tomography (CT) is routinely used to complementconventional digital subtraction angiography for transcatheter therapy. The goal of the present report is to shareexperience with the use of C-arm CT in hepatic interventions, with the aim to provide practical tips for optimizingimage acquisition and postprocessing. Although the authors’ direct experience is limited to the equipment of a singlemanufacturer, many of the principles and guidelines can be readily extrapolated to other C-arm CT systems.

J Vasc Interv Radiol 2010; 21:1817–1823

Abbreviations: DSA � digital subtraction angiography, FOV � field of view, MIP � maximum-intensity projection, MPR � multiplanar reconstruction, 3D �three-dimensional

C-ARM computed tomography (CT)uses the principles of cone-beam CTproducing multiplanar CT-like softtissue images and three-dimensional(3D) volume-rendered images from asingle rotational acquisition (1–3). Thisability has resulted in an innovativetechnique for image guidance of intra-

From the Department of Interventional Radiology,Stanford University Medical Center, 300 Pasteur Dr.,H3630, Stanford, CA 94305. Received June 29, 2009;final revision received July 15, 2010; accepted July31, 2010. Address correspondence to N.K.; E-mail:kothary@stanford.edu

N.K. and A.T. received a research grant from Sie-mens Healthcare Sector (Forchheim, Germany).G.H. is a paid consultant for, and received a researchgrant from, AngioDynamics (Queensbury, NewYork). L.H. serves as a paid speaker for Cook(Bloomington, Indiana) and Portola Pharmaceuticals(South San Francisco, California); received grantsupport from AngioDynamics; is a paid consultantfor Omnisonics (Wilmington, Massachusetts); andserves on the Scientific Advisory Board for BacchusVascular (Santa Clara, California). D.S. serves as apaid consultant for MediGene (San Diego, Califor-nia), Jennerex Biotherapeutics (San Francisco, Cali-fornia), and Lunar Design (San Francisco, Califor-nia). D.S. and L.H. are shareholders in, and serve on,the Medical Advisory Board for Nitinol Devices andComponents (Fremont, California).

© SIR, 2010

DOI: 10.1016/j.jvir.2010.07.027

vascular interventions. C-arm CT wasfirst developed for application in neu-rointerventional procedures (4,5); withimprovement in technology, availabil-ity of flat-panel detectors and im-provement in image quality, C-arm CThas found applications for abdominalinterventions (1,6,7). At the time of thepresent writing, three C-arm CT–capablesystems are commercially available in theUnited States: DynaCT (Siemens,Forchheim, Germany), XperCT (Phil-lips, Eindhoven, The Netherlands),and Innova CT (GE Medical Systems,Waukesha, Wisconsin).

At our institution, we routinely useC-arm CT (eg, DynaCT) for all transhe-patic arterial therapies such as chemo-embolization and radioembolization forprimary and secondary hepatic malig-nancies. The advantage of the use ofC-arm CT for transhepatic arterial inter-ventions is the ability to obtain CT-likemultiplanar views during injection ofcontrast medium in the hepatic arteryand provide 3D maximum-intensityprojection (MIP) reconstructions of thehepatic vessels (Fig 1). The present re-port has the goal of sharing experiencewith C-arm CT in hepatic interven-tions in an effort to provide useful tips,

from setup to image reconstruction,

for a time-efficient use of the C-armCT system. Some of the techniquesand terminology reported here arespecific to the equipment of one man-ufacturer, but other, more genericstrategies such as patient positioningcan be applied to all C-arm CT sys-tems. In addition, we note that the fewvendor-specific techniques are for il-lustrative purposes only and are notmeant to imply superiority of any onesystem over another. Details on theprinciples of cone-beam CT imagingand C-arm CT have been describedelsewhere (8,9) and are beyond thescope of this report.

C-ARM CT SYSTEM

Presently, our interventional radiol-ogy suites are equipped with AxiomArtis dTA ceiling-mounted systems(Siemens) with flat detectors (30 � 40cm, 48 cm diagonal, 154-�m pixelsize). These systems allow for a spatialresolution of 3.25 line pairs per milli-meter and adequate contrast resolu-tion for soft tissues. For high-quality C-arm CT images, the C-arm itself should becapable of high-speed movements, prefer-ably up to 60°/seconds, acquiring 60frames/seconds. This allows for expedi-

tious acquisition in rotational and orbital

1817

1818 • C-arm CT for Hepatic Interventions: A Practical Guide December 2010 JVIR

directions within a single breath-hold. Inaddition to high-speed acquisitions, thepostprocessing software platform itselfshould be efficient, allowing the operatorto view reconstructed images promptly.At our institution, our C-arm CT sys-tems are equipped with software levelVB31 that currently allows the syngoDynaCT software platform to effi-

Figure 1. Axial C-arm CT of the liver sh54-year-old man with hepatitis C–related cirthe axial plane with injection from the coenhancing tumors consistent with the patielar carcinoma.

Axiom Artis dTA System Setup: Organ

Parameter Value

Output 90 kVPulse width 5.0 msRadiation dose 0.36 �Gy/frame

Focus LargeKv focus OffPixel resolution LowGain correction 0.0Edge enhancement 20%Window center 1,800Window width 3,200Dyna time 8 sAngulation step 0.5°/frameDyna control Auto

ciently reconstruct high-quality C-arm

CT images. However, we would liketo note that, with new applicationsand/or improvement in the technol-ogy, C-arm CT systems will continueto see a steady need for imaging plat-form and software updates that willincur additional costs. At the time ofthis writing, the next generation of C-arm CT capable angiographic systems

s multifocal hepatocellular carcinoma in asis. Contrast-enhanced C-arm CT image inon hepatic artery demonstrates multiple

s known history of multifocal hepatocellu-

gram

Notes

——

Important not to increase dose fromthis setting

—————

Can be adjusted per user preferenceCan be adjusted per user preference

———

and software updates has already be-

come commercially available, capableof faster reconstructions and someadded applications.

For hepatic interventions, we use an8-second rotational scan of 210° and 26°rotation/sec, image acquisition every0.5° for a total of 419 images, 512 � 512voxel matrix, source power of 125 kVp,and receiver dose of approximately 0.36�Gy per frame. A brief overview of theorgan program setup used at our insti-tution (DynaCT) is presented in theTable. Similar programs, although notidentical, are available on the other C-arm CT systems.

Data acquired from the rotational ac-quisition are automatically postpro-cessed. These reconstructed images canthan be viewed in multiple planes aswell as manipulated by the operator. Atour institution, all C-arm CT images arepostprocessed, reconstructed, and ma-nipulated on a separate 3D workstation(syngo-X), placed in the control roomnext to the standard “live monitor” usedfor viewing live fluoroscopy and digitalacquisitions. This allows the operator toreview the digital subtraction angiogra-phy (DSA) and C-arm CT images simul-taneously, which not only increases op-erator ease, but also helps to solveproblems in difficult cases in whichDSA and C-arm CT complement eachother. In the suite itself, the C-arm CTimages can be reviewed on an addi-tional monitor using an “electronic con-trol console,” which has a joystick thatworks as a mouse.

PATIENT SETUP FORABDOMINALINTERVENTIONS

Room and patient setup is a funda-mental step to maintain efficiency dur-ing procedures that would benefit fromC-arm CT imaging. The goal is to beable to switch between DSA and C-armCT without having to reposition the pa-tient or lose precious time between thetransitions. The following time-savingsteps are universal and are applicable toall C-arm CT systems.

Patient Position

Unlike DSA imaging, C-arm CT mayrequire what is known as “offsetting.”This term is used in reference to posi-tioning the patient on the table (Fig 2).For example, if the tumor to be treated is

owrhommnt’

Pro

located in the peripheral portions of the

CT

Tognolini et al • 1819Volume 21 Number 12

right lobe of the liver, the patient shouldbe positioned such that (s)he is justslightly off center to the left of the table.Similarly when the region of interest isin the left lobe of the liver, the patient isoff center slightly to the right. In doingso, the operator ensures that the regionof interest is as close to the center of thefield of view (FOV) as possible. Often,when patients are not offset, the opera-tor may need to move the table too far tothe left or right to move the region ofinterest to the center of the FOV, whichcan result in insufficient room for the200° C-arm sweep and inability to per-form a test run or an acquisition as aresult of insufficient clearance. Position-ing the patient correctly on the table be-fore draping the patient eliminates theneed to reposition the patient at the timeof C field of view CT, maintaining effi-ciency and, more importantly, the steril-ity of the procedure.

Placement of Monitoring Devicesand Intravenous Drip Poles

Any device that can be a potentialobstacle during the C-arm rotation

Figure 2. The patient’s position may needtable to include the region of interest complcentral beam to be centered on the regionensuring complete coverage for the C-arm

should be positioned outside the rota-

tion trajectory. This includes polesfor intravenous drips, pulse oxime-try cables, and leads for electrocar-diographic monitoring. Objects thatcan cause streak artifacts (eg, jewelry,electrocardiographic leads) shouldalso be situated outside the FOV. Atour institution, we use radiolucentelectrocardiographic leads (Red Dot;3M, St. Paul, Minnesota), with theelectrocardiography box located un-der the table bottom end. Setup ofpoles for intravenous drips, bloodpressure cuffs, and pulse oximeters issuch that a complete C-arm CT rota-tion can be performed without the C-arm snagging on the tubes or cables(Fig 3a, b). Tubing for intravenous flu-ids and medications required to behung from a pole, as well as the tubingfor nasal oxygen required through theprocedure, is positioned at the head ofthe table, cranial to the C-arm. Thisprevents the tubing from gettingcaught or entangled with the x-raysource during the 200° sweep of the C-arm during a CT acquisition. Similarly,the blood pressure cuff and pulseoximeter device are placed on the lower

be offset with respect to the center of they in the FOV for C-arm CT. This allows thenterest, rather than the center of the table,acquisition.

extremities. If the lower extremities are

unsuitable for accurate monitoring, thedevices can be placed on one of thearms, ensuring that the junction be-tween the cuff and inflation tube andtransducer is easily accessible duringthe procedure, allowing for a quick tem-porary disconnection during C-arm ro-tation.

Positioning the Patient’s Arms

For angiographic studies, it is notuncommon to position the patient’sarm by their side. However, streak ar-tifact from the forearms can lead toimage degradation of the C-arm CTimages. Hence, ideally for C-arm CTacquisitions, the arms should be posi-tioned above the head, a position sim-ilar to that required for a routine heli-cal CT. Unfortunately, maintainingthis position through the entire proce-dure is difficult and can lead to shoul-der and arm strain. Positioning andrepositioning the arms by the patient’sside can be time-consuming and car-ries the risk of compromising the ster-ile field, and is therefore less thanideal. To maintain patient comfort andmaintain efficiency, we position thepatient’s arms on a butterfly-shapedarmrest device (Fig 3a–c), which wascustom-made for our institution. Sim-ilar armrests are now available com-mercially from Siemens. On devicessuch as these, the arms are at an angle70°–90° to the torso and the forearm isflexed at the elbow and is at a 90°angle to the arms (Fig 3a,b). In ourexperience, this relieves the strain onthe shoulders, and most patients areable to maintain this position through-out the procedure while keeping theupper extremities out of the FOV andthe C-arm trajectory.

Contrast Agent Injectors

C-arm CT requires the use of di-luted iodinated contrast medium (asdetailed later), whereas DSA requiresfull-strength iodinated contrast me-dium. To maintain efficiency, our in-terventional suites are equipped withdouble-barrel contrast agent injectors(Mark V ProVis; Medrad, Warrendale,Pennsylvania). Routinely, for all pro-cedures that use a combination of C-arm CT and DSA, one barrel is loadedwith full-strength iodinated contrast me-dium (Omnipaque 300 or Visipaque 320;

toetelof i

Mallinckrodt, St. Louis, Missouri) for

1820 • C-arm CT for Hepatic Interventions: A Practical Guide December 2010 JVIR

standard DSA imaging and the otherbarrel is loaded with the same contrastmedium diluted to 150 or 160 mg/mLiodine concentration for C-arm CT ac-quisitions. In our experience, the useof dilute iodinated contrast agent notonly reduces the contrast agent bur-den on the kidneys while maintainingthe same image quality, but, more im-portantly, reduces the streak artifacton the CT-like soft tissue images ob-tained by C-arm CT. Sterile injectortubes are attached to both barrels (Fig3d) and marked appropriately withsterile color-coded stickers. Havingthis set up before the procedure isstarted enables the operator to effi-

Figure 3. Appropriate patient setup is esseCT. (a) Cranial view of a patient positionedis positioned off center to the left to allow aHis arms are positioned on a butterfly-shapassociated tubing (arrows) is at the head ofC-arm CT rotation. (b) Similar image ofthe arms and the intravenous pole. The bloat the ankle (not shown). (c) Close-up vieallow comfortable positioning of the armsinjector preloaded with full-strength andinjector tube is attached to each barrel and mallows for convenient and expeditious switDSA and half-strength contrast agent for Cjvir.org.)

ciently switch between DSA and C-

arm CT by attaching the appropriatetubing.

By following these steps beforestarting the procedure, we ensure safe,efficient, and seamless C-arm CT ac-quisitions.

C-ARM CT SETUP AND SCANPARAMETERS FORABDOMINALINTERVENTIONS

The first step before obtaining anyC-arm CT scan is to perform a testrotation to ensure that the C-arm canrotate unobstructed. Presently all C-arm CT systems require similar test

al to maintain efficiency while using C-armexpedite C-arm CT acquisition. The patientuate imaging of the right lobe of the liver.armrest device. The intravenous pole and

e table and hence away from the arc of thevolunteer demonstrating the position ofpressure cuff in both patients was placed

of the butterfly-shaped armrest device toough out the procedure. (d) Double-barrellf-strength iodinated contrast agent. An

ked appropriately at the time of setup. Thisng between full-strength contrast agent forrm CT. (Available in color online at www.

runs to avoid table collision during the

actual rotational acquisition. The testrotation for DynaCT is done in twosteps: isocentering on two views 100°apart (usually anteroposterior and leftor right anterior oblique depending onthe position of the C-arm in respect tothe table) followed by the selectionof the scanning C-arm position preset.At our institution, the preferred presetis a 48-cm FOV, with a 0° anteropos-terior and a 100° left anterior oblique(or right anterior oblique if the C-armis positioned on the right side of thetable) position.

For abdominal C-arm CT acquisi-tions, we use the 8-second rotationalacquisition. For operator convenience,the tab to select this program is placedadjacent to standard mesenteric DSAimaging protocols on the electroniccontrol console for the angiographictable (Fig 4). Other possible options in-clude a shorter (5 seconds for DynaCT) orlonger (20 seconds for DynaCT) scan du-ration. Both these alternatives have ad-vantages and disadvantages: the 5-secondrotation is useful in patients who are un-able to hold their breath, but is limited inits resolution by the corresponding de-crease in the number of images ob-tained. The 20-second acquisition, con-versely, has excellent resolution, but isseverely limited by the long breath-hold as well as motion artifact fromadjacent moving structures such asperistaltic bowel as a result of the longscan time. Hence, at our institution,we routinely use the 8-sec acquisitionas an acceptable solution.

Typically in patients who havenever undergone previous chemoem-bolizations, we obtain two sets of C-arm CT images. The first one is ob-tained during the injection of contrastmedium in the common or proper he-patic artery to identify and character-ize tumors to be targeted and to planthe treatment, and the second set is anunenhanced (ie, noncontrast) set ob-tained after delivery of the chemother-apeutic agents to assess adequacy oftumor treatment. Ethiodol uptake inthe tumor is assessed as a surrogatemeasure of completeness of tumortreatment, triggering additional selec-tive catheterizations if incomplete up-take is observed. In patients with ahistory of chemoembolizations, a non-enhanced C-arm CT scan is obtainedbefore the contrast-enhanced study toallow the operator to distinguish areas

ntitodeqedthaodwthr

haar

chi-a

of residual Ethiodol uptake from areas

g.)

Tognolini et al • 1821Volume 21 Number 12

of tumor enhancement. Additional C-arm CT images are occasionally ob-tained during the procedure if neededto solve problems.

CONTRAST AGENTINJECTION PROTOCOL

The contrast-enhanced acquisitionsare obtained with the use of diluteiodinated contrast agent (Omnipaque300 or Visipaque 320; Mallinckrodt)diluted to 150 or 160 mg/mL iodineconcentration with equal volume ofnormal saline solution.

Initial contrast-enhanced imageswith injection of the common orproper hepatic artery are routinely ac-quired by injecting at a rate of 2 mL/sec for a fixed duration of 12 seconds(total of 24 mL) and an imaging delayof 4 sec. Injection rates and relativetotal contrast volumes for more selec-tive catheterizations vary according tosize of the artery and type of micro-catheter, usually from 0.1 mL/sec to1.5 mL/sec with a fixed injection du-ration of 12 sec.

We found that a 4-sec imaging delaywith the 8-sec acquisition time with in-jection of contrast agent through the en-tire 12 seconds allows the iodinated con-

Figure 4. MPR images of a single C-armtranshepatic arterial chemoembolization dleft), coronal (top right) and axial (bottom leagent injection. The reference lines can funcan be used to identify the tumor in allneously. (Available in color online at www

trast agent to enhance parenchymal

tissue before the start of data acquisitionand maintains maximal enhancement ofthe vessels throughout the acquisition.For vessels that may take a long, tortu-ous course such as extrahepatic supplyfrom an omental branch, a longer acqui-sition time or a longer x-ray delay maybe needed.

IMAGING RECONSTRUCTIONAND POSTPROCESSING

The exact steps for 3D image recon-struction and ease of postprocessingmay differ among equipment vendors,but all systems ultimately result inmultiplanar images and a volumetricdataset (eg, MIP) that can be manipu-lated. In the next few paragraphs, webriefly describe our experience withimage manipulation to obtain high-quality C-arm CT images that providethe most useful information. Althoughour experience is specific to DynaCT,we believe that a similar workflow canbe undertaken with the other systems,bearing in mind that the same functionmay be termed differently in other C-arm CT systems.

After an acquisition, the volumetricdata are sent to the syngo-X workstationfor 3D image reconstruction using

acquisition from alaying sagittal (top

images after contrastn as cross-hairs andree planes simulta-

r.org.)

Figure 5. Simultanepreloaded data (eg,arm CT and postchdemonstrate Ethiodochemoembolization)of the entire tumor(DynaCT). The “stacentire selected imagonline at www.jvir.or

syngo InSpace (ie, 3D volume render-

ing) and syngo DynaCT options. Imagecorrection algorithms are applied auto-matically for scatter, beam hardening,ring artifact, and truncation. In our ex-perience with the current software sys-tem, postprocessing is generally accom-plished in less than 1 minute.

Multiplanar Reconstructions

For 3D multiplanar reconstructions(MPR), the image volume needs to beloaded onto the 3D task card for theDynaCT software. The 3D image dis-play is subdivided in three segmentsdisplaying, respectively, each of thethree perpendicular reconstructionplanes: sagittal, coronal, and axial (Fig4). The following adjustments can bemade to optimize the multiplanar im-ages.

Slice thickness.—Default thin slices(� 1 mm; 0.83 mm with DynaCT) canbe extremely useful in visualizingsmall tumors or branch vessels, but itcan also lead to poor signal-to-noiseratio. This can be improved by increas-ing the slice thickness. On DynaCT,slice thickness can be increased usingthe MPR thick mode icon on the sub-task card. The default slice thicknessfor the thick MPR is usually set at 5

s viewing of two volumes of acquired ortrast-enhanced prechemoembolization C-

oembolization unenhanced C-arm CT toptake, as depicted in this image and afterconfirm adequate coverage and treatment

his is done with the viewing task cardode” icon (1) allows for uploading the

olumes in each panel. (Available in color

CTispft)ctio

th.jvi

ouconeml ucan. Tk m

e v

mm, but it can be manually changed

ctio rg.

1822 • C-arm CT for Hepatic Interventions: A Practical Guide December 2010 JVIR

by right-clicking the MPR thick iconand entering the desired thickness inthe pop-up box. We have found thatthis is especially helpful in the coronalplane, where MPR images of 7–10-mmthickness can demonstrate the vessel(s)supplying the tumor with soft-tissue land-marks and serves as a roadmap, similar to3D MIP images. However, unlike MIP im-ages, these images are often difficult torotate.

Window and contrast levels.—Similarto slice thickness, the window andcontrast level values can be set as de-faults or individually adjusted foreach patient by using the middle but-ton on the mouse.

Isocentering of the treatment target.—The best way to display the hepatictumor(s) and their vascular feeders isto isocenter the reconstruction planesto the tumors by moving the cross-reference lines from the center of thescreen to the center of the lesion. Thethree MPR planes are reconstructed onthree perpendicular planes 90° apart,but the angulation between planes canbe changed by rotating the cross-refer-ence lines as needed on the syngoworkstation.

Image registration.—A feature onDynaCT is the ability to fuse two vol-ume sets on the 3D task card. Thisprocess allows the operator to fuse

Figure 6. MIP on the InSpace task card. (C-arm angulation is depicted in the top rigthe vascular anatomy. The simplest way, woutlined using the “VOI punching” icon (2best lay out overlapping vessels and identifDSA acquisitions in multiple oblique proje

two sets of images (contrast-enhanced

prechemoembolization C-arm CT andunenhanced postchemoembolizationC-arm CT or pretreatment diagnosticCT, positron emission tomography/CT, or magnetic resonance imagingwith C-arm CT images). Images fromthe two sets can be viewed superim-posed on each other, with differentcolor scales to distinguish one fromthe other or side-by-side with simulta-neous scrolling. We have found thisfeature useful in patients with multi-ple segmental arteries feeding the tu-mor, to evaluate and ensure completegeographic uptake of the chemoem-bolic drugs. For systems that do nothave this upgrade, a similar compari-son can be done manually. Both setscan be viewed on the workstation un-der the “Viewing” task card and bysetting the monitor to display twopanels (two panels are obtained by se-lecting 2:1 under “View” on the toptoolbar). The two volumes can be loadedand scrolled side by side using the stackmode (Fig 5). Limitation of using this taskcard is that it allows for viewing axialimages only.

MIP Images

Cases with difficult anatomy maybenefit from MIP reconstructions ofthe contrast-enhanced C-arm CT im-

Rotated MIP image that best lays out the ocorner, a useful tool for the operator. (b) Icelieve, is to orient the image in the caudocsted under the “Tools” subtask card. The fe vessel to be selectively catheterized, allons. (Available in color online at www.jvir.o

ages. All C-arm CT systems are capa-

ble of generating a volumetric recon-struction. DynaCT generates volume-rendered reconstruction from the imagesloaded on the 3D task card and are readyto be viewed and manipulated on the “In-Space” task card (Fig 6a). In our experi-ence, optimal 3D imaging of the vas-culature can be achieved as follows.The acquired contrast-enhanced or un-enhanced volume is first loaded in theInSpace task card. Image manipula-tion is then performed by first adjust-ing the window and center level tobest opacify the vessels. This often re-quires converting the images from“VRT” to “MIP” images. Next, skeletalstructures and nontarget solid organs(eg, kidneys) can be cropped to isolatethe vasculature (Fig 6b). Althoughvarious methods can be used to dothis, we have found that the quickestway to crop out the undesired ana-tomic structures is to select the cau-docranial view (with the “Orient”sutask card on DynaCT; Fig 6b). Thevolume of interest is then outlined.The final 3D vascular map can befreely rotated to best lay out overlap-ping vessels and identify the vessel tobe selectively catheterized, allowing forplanning that eliminates the need forDSA acquisitions in multiple obliqueprojections. A handy timesaving tool of-fered by DynaCT is a dedicated icon

in of a segment VII hypervascular tumor.s required to create a MIP image to isolateial view (1). The volume of interest is thenl 3D vascular map can be freely rotated tog for planning that eliminates the need for)

a) right one b ran), li inay th win

listed under subtask card “X-ray” that

Tognolini et al • 1823Volume 21 Number 12

allows the operator to move the C-armto match the tube orientation chosen onthe Inspace image by the mere push of ajoystick.

DISCUSSION

At the time of writing, we havebeen using C-arm CT for more than 3years and have performed approxi-mately 800 hepatic interventions witha combined approach of DSA and C-arm CT. CT-like multiplanar views ob-tained form C-arm CT during injectionof contrast medium in the hepatic ar-tery have helped us identify and char-acterize tumors that are not clearlycharacterized on DSA or cross-sec-tional imaging (10), as well as differ-entiate pseudolesions (eg, arteriopor-tal shunts or degenerative nodules)from tumors without moving the pa-tient to a dedicated CT scanner (6).The 3D MIP reconstruction of the he-patic arteries is an important problem-solving tool for patients with difficultanatomy, especially in patients with“corkscrew” vessels caused by under-lying cirrhosis. Three-dimensional map-ping helps identify the arterial supply tothe tumor, allowing superselectivecatheterization that targets the tumorwhile decreasing the collateral dam-age to uninvolved liver parenchyma(10). C-arm CT also provides crucialinformation in patients with tumorsthat have extrahepatic supply, in tu-mors that are located in a segment thatmay have more than one segmentalbranch supplying it (eg, segment IV),or in isolating viable regions of previ-ously chemoembolized tumors wheredense Ethiodol retention obscures ar-eas of enhancement after administra-

tion of contrast medium on uniplanar

DSA images (10). Finally, C-arm CTcan identify critical, nontarget areas ofperfusion such as the stomach, as wellas confirm adequate treatment of thetumor itself, hence increasing operatorconfidence (10,11).

As any new modality, the learningcurve can be steep, but with routineuse and increasing comfort level forthe staff and the physicians, our timeto switch from DSA to C-arm CT, theactual C-arm CT rotation, and thetransfer of images to the workstationis now less than 3 minutes. This isdrastically less time than reported byearly users of C-arm CT (12), in partbecause of advancement in the tech-nology itself, but also because of thestaff’s understanding of the modalityand hence of positioning and settingup the room correctly and consis-tently. Finally, as a result of increasingcomfort and confidence in the modal-ity, operating physicians can now re-view, analyze, and manipulate imagesquickly, again maintaining efficiencyand making C-arm CT an integral partof our arsenal.

Acknowledgments: The authors thankTeri Moore (Research Collaborations Man-ager, Siemens AX), Kim Reed, RT, andShad Afshar, RT, for technical support.

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