MRI, the lesions were best visualized in T1W-VIBE orpost-contrast and GRE sequences. DWI/ADC showed re-stricted diffusion in the lesions. A size difference of 1.4 �4.5 mm (p�0.335) was found between MR/CT and grossmeasurement. H&E and Von Kossa staining showed com-plete cell death with a sharply demarcated margin betweenthe ablated and non-ablated zone. Bile ducts and vesselswere completely preserved. Focal hepatocellular regenera-tion was found in as early as 7 days post-IE. Areas ofcomplete cell death stained nearly 100% with apoptoticmarkers (TUNEL, BCL-2, Caspase-3). Complete preserva-tion of vessels were seen on vWf and VEGFR. No compli-cations were noted peri- or post-procedure.

CONCLUSION: 1. With real-time monitoring and well-controlled focused cell death of the target tissue, irreversibleelectroporation can be a novel and effective ablative methodin hepatic tumor. 2. MRI, CT or US can be efficiently usedfor monitoring and characterization of IE ablated area peri-or immediately post-procedure.

Abstract No. 334

Safety and Therapeutic Effect of RFA Combined withTAE in Rabbit VX2 Liver Tumors.S. Li, R. Ni, L. Chen; First Affiliated Hospital of SoochowUniversity, Suzhou, Jiangsu, China

PURPOSE: To investigate safety and efficacy of radiofre-quency ablation (RFA) combined with transcatheter arteryembolization (TAE) on treatment of VX2 liver tumor ofrabbit model.

MATERIALS AND METHODS: Thirty six rabbits with im-planted VX2 liver tumors were divided into 4 groups ran-domly. Group 1 served as control and received RFA only(n�9). Group 2, 3, and 4 received TAE and RFA (n�9 ineach group). RFA was performed in day 1, 4, 7 after TAErespectively in study groups. Hepatic artery was embolizedwith lipiodol alone. Liver (ALT) and kidney (UREA) func-tion of rabbit model were tested before procedure, 1, 4, and7days after procedure respectively. 2, 2, and 5 rabbits weresacrificed for tumor harvest 1, 4, 7 days after RFA orTAE�RFA respectively. Maximal diameter of coagulationnecrosis were recorded 7 days after study. Macroscopic andmicroscopic studies were also performed 1, 4, and 7daysafter.

RESULTS: There were seven rabbits died: 2 in group 1, 3 ingroup 2, 2 in group 3. All deaths happened in 24 hours afterprocedures. Value of ALT was elevated with worst seen ingroup 2 (385.0 � 213.1IU/L), and mildest in group 1 (P �0.05). ALT started to improve 4 days after. In group 1, ALTreturned back close to baseline after 7 days, which wassignificantly better than that seen in study groups. ALTvalue worsening was significant between group 3 and group1(p � 0.05), but it was not significant between group 4 andgroup 1(p � 0.05). There were no significant changes inUREA value in all groups (p � 0.05). Ablated zone wassignificantly larger in all therapeutic groups than that ingroup 1 (p � 0.01), but there were no differences amongstudy groups (p � 0.05).

CONCLUSION: RFA of VX2 liver tumor combined withTAE could evidently enlarge necrotic zone and may pro-duce complete necrosis. However, RFA combined withTAE may impair liver function significantly when RFA

performed within 4 days after TAE. Liver function impair-ment becomes less significant if RFA done 7 days afterTAE. There was no obvious impact on renal function of inall groups.

Abstract No. 335

CT Imaging of Ablation Zones after RadiofrequencyAblation (RFA) of Kidney Tumors.P.P. Sarlieve, J.R. Kachura; Toronto General Hospital andMount Sinai Hospital, Toronto, ON, Canada

PURPOSE: To determine the imaging features of ablationzones on triphasic CT scanning following RFA of kidneytumors.

MATERIALS AND METHODS: All patients with kidneytumors treated with RFA at Toronto General Hospital andMount Sinai Hospital since 2004, whose imaging follow-upconsisted of triphasic CT scanning, were analyzed. Tumorpathology and size were noted. Typical CT follow-up wasperformed one month post-ablation and every 4-6 monthsthereafter. CT features evaluated included ablation zonesize, attenuation, enhancement, and ancillary findings suchas halo sign in perinephric fat.

RESULTS: The patient cohort consisted of 33 patients (27M, 6 F) with mean age 61 years (range 45-82). 37 tumorswere treated, all using multi-tined LeVeen electrodes: 29patients had a solitary tumor, whereas 4 patients had twotumors ablated each. Mean maximum tumor diameter was2.3 cm (range 1.1-4.2). Pathological confirmation was ob-tained for 27 tumors (73%): there were 24 renal cell carci-nomas and 3 oncocytic neoplasms. Mean CT imaging fol-low-up was 13 months (range 0.3-43). Ablation zonediameter was 10% larger than tumor diameter, on average,on the first follow-up CT, and then decreased to 7% smallerthan the original tumor at 10 months and 19% smaller at 27months post-ablation. Excluding 3 tumors containing calci-fications, mean ablation zone attenuation was 40 � 15Hounsfield Units (HU) at initial follow-up, and 27 � 7 HUat 33 months. One patient had obvious enhancing residualtumor tissue at initial follow-up which was successfullyablated with a second procedure. Another patient developedan enhancing nodule at the edge of the ablation zone at 35months which was found to be chronic inflammation and fatnecrosis on pathology. The halo sign, consisting of curvi-linear soft tissue attenuation in perinephric fat, was notedaround 16 ablation zones (43%), first identifed at a mean of11 months post-ablation (range 5-13).

CONCLUSION: After RFA of kidney tumors, ablationzones are initially larger than the treated tumors and thengradually decrease in size. The halo sign is a commondelayed finding in perinephric fat post-ablation. Enhancingtissue related to the ablation zone may correspond to anon-malignant phenomenon.

Abstract No. 336

Injection Techniques for Thermochemical Ablation.B.C. Smith, L.A. Freeman, B. Anwer, T.L. Brix,E.N.K. Cressman; University of Minnesota Medical School,Minneapolis, MN

PURPOSE: To evaluate injection techniques for thermo-chemical ablation in an ex-vivo pig liver model as a newmethod for tumor ablation.

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MATERIALS AND METHODS: 28 injections into explantedpig liver were performed in quadruplicate (112 total) andtemperature profiles recorded. Using a coaxial injectiondevice with an acid and base, concentrations raging from1M-15M (total volumes 0.5-1.0ml) were injected into liverover 1 minute. Various configurations and techniques weretested. A thermocouple probe placed 1 cm from the devicetip allowed collection of temperature data at 15 secondintervals for 5 min. Temperature changes for each experi-ment were recorded. Ablation volumes derived from slicethickness and surface area were calculated with ImageJsoftware available from the NIH.

RESULTS: Injections performed at the liver lobule periph-ery were more satisfactory due to decreased tendency of thereaction to track into major vessels. As anticipated, highesttemperatures occurred with simultaneous injection of higherconcentration reagents. Maximum temperatures were at-tained between 30-45 seconds, with temperature changes asgreat as 57°C. Retraction of the inner coaxial needle up to2 cm generally increased temperature profiles. Coagulationzone volumes were variable, but ranged up to 11 cc.

CONCLUSION: Our data suggest that simultaneous injec-tion of higher concentration acid and base leads to bothgreatest temperature increase and coagulation volume. Thehighly vascular nature of the normal liver makes peripherallobular injection the most promising site for ex-vivo injec-tion analysis.

Abstract No. 337

Clinical Outcomes of Radiofrequency Ablation for Colo-rectal Cancer Hepatic Metastases.C.T. Sofocleous, E.N. Petre, I.K. Ip, S. Solomon, R. Thornton,A. Covey, L. Brody, W. Alago, M. Maybody, G. Getrajdman,K.T. Brown; Memorial Sloan Kettering Cancer Center,New York, NY

PURPOSE: To update the clinical outcomes of radio-frequency ablation (RFA) of hepatic colorectal metastases.

MATERIALS AND METHODS: Review of a prospectivelycreated HIPPA compliant RFA database identified 54 pa-tients with 65 hepatic colorectal metastases treated by CTguided RFA between December 2002 and June 2007. Wereviewed medical records and relevant imaging to deter-mine technical success (no enhancing tumor at 6 weeks postRFA contrast CT), complications and local tumor progres-sion (LTP). LTP-free and overall survivals were calculatedusing Kaplan Meier Methodology.

RESULTS: Median and mean lesion size was 2 and 2.4(range: 0.6-7) cm. Technical success was documented in60/65 (92.3%) lesions. Failures were the result of poorvisualization and inadequate tumor targeting, large size, orproximity to blood vessel. Median survival was 35 months.One, 2 and 3-year survival rates were 89.8%, 63.3% and40.1% respectively. Twenty nine/65 (45%) lesions pro-gressed within 1 to 32.7 months after RFA. Median primaryand assisted (including repeat RFA) LTP-free survival were14 and 24 months respectively. Primary and assisted LTP-free rates were 51.4% and 75% at 1 year, 39.2% and 50%,at 2 years, and 12.5% and 24.5% at year 3. Tumor size over3 cm was an independent factor of LTP (P � 0.01). Therewere 4 minor complications.

CONCLUSION: Despite a relatively high rate of LTP, 1, 2,and 3 year LTP-free survivals of 75%, 50% and 25% can beexpected when patients are retreated.

Abstract No. 338

Utility of Renal Artery Coiling in Conjunction withRadiofrequency Ablation.C.R. Wehbe,1 S. Rafie,1 P. Kang,2 S.G. Nour;1 1UniversityHospitals Case Medical Center, Cleveland, OH; 2LouisStokes Cleveland Department of Veteran Affairs MedicalCenter, Cleveland, OH

PURPOSE: To evaluate safety and utility of percutaneousradiofrequency ablation (RFA) performed in the vicinityand in direct contact with intravascular occlusion coils. Thiswill hopefully pave the way for novel neoplasm, and AVMtreatment.

MATERIALS AND METHODS: Eleven percutaneousRFA’s were preformed in the kidneys of 6 pigs followingselective renal artery occlusion using platinum and steelcoils. Randomly selected renal artery branches were oc-cluded under fluoroscopy for guidance. Ablations were pre-formed for 10 minutes using a 17 gauge, 1 cm exposed-tiptitanium radiofrequency electrode with simultaneous re-cording of temperature. Ablated kidneys were harvested forsubsequent histopathological analysis. The distance be-tween RF electrode tip and vascular occlusion coil wasaccurately measured on each of the gross pathological spec-imens. Histological specimens were examined for regularityof ablation zones and for any evidence of associated vas-cular damage as a result of inadvertent coil heating.

RESULTS: Ablations were successfully created in all 11attempts without intraprocedural complications. RF elec-trode-to-vascular coil distance ranged from 0 to 22 mm andwas inversely proportional to recorded temperatures. Theaverage (� SD) RF electrode tip were 85.8 � 14.9 °C forthe platinum coils and 85.2 � 14.9 °C for the stainless steelcoils. The average vascular coil temperatures were 41.1 �2.5 °C for the platinum coils and 40.2 � 3.0 °C for thestainless coils. The ablation zone size ranged on the order of1.1 cm � 1.5 cm in length and width respectively. Therewas no histopathological evidence of tissue necrosis, orother signs of damaging vascular heating in neither plati-num nor stainless coils.

CONCLUSION: Results of this preliminary investigationindicate the safety of percutaneous renal RF ablation pro-cedures performed as close as 0 mm from vascular occlu-sion coils (with coil touching the RF probe), without result-ant significant coil heating or alteration of RF current. Thisdata consistently demonstrated the safety of radiofrequncyablations in contact to a vascular coil. This sets the stage forthe use of a combination therapy as future clinical therapiesor research for tumor management.

Abstract No. 339

The Effects of Arsenic Trioxide on Radiofrequncy Ab-lation: Intraarterial Versus Intervenous Administration.C. Yoon, S. Kang, K. Hong, H. Choi; Seoul NationalUniversity Bundang Hospital, SungNam, KyeongKi-do, Ko-rea

PURPOSE: Arsenic trioxide (AS2O3) has antivascularproperties, and can be used as a possible pharmaceuticalalternative that augments radiofrequency (RF) ablation byreducing tumor blood flow. The aim of this study was toassess the effects of intraarterial and intravenous adminis-tration of AS2O3 on RF-induced coagulation in experimen-tally induced liver tumor.

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