Abstract No. 333: Evaluation of Irreversible Electroporation (IE) in a Swine Study: A New Non-Thermal Tumor Ablation Technique

diameter. The array diameter was chosen according to the tumor diameter. The maximum power output and total ablation time were 80-190 W, and 25-68 minutes, respectively. RESULTS: The thermally injured nerves consisted of phrenic nerve (n⫽3) and brachial plexus (n⫽1). In every patient, the procedure was completed successfully. During procedure, severe shoulder pain appeared in one patient, toothache in one, and no pain in 2. The tumor location of the patient with phrenic nerve injury is adjacent to right atrium, pulmonary trunk, or medial aspect of right diaphragm, and that with brachial plexus injury is in the top of left pulmonary apex. All nerve injuries were found several days after the procedures, presented by marked diaphragmatic elevation of affected side, or motor and sensory palsy at ulnar side of left forearm. All nerve injuries improved to some extent, but still remained in existence during follow-up period. However, no local tumor progression was seen in all ablated tumor. CONCLUSION: Thermal nerve injury is a rare but considerable complication after RF ablation for lung tumor. We should pay attention to the tumor location, especially positional relation between the tumor and mediastinal structures or pulmonary apex. Abstract No. 331 Percutaneous Radiofrequency Ablation for Primary Breast Cancer with Overlapping Technique. T. Ito, H. Mizuno, T. Mizushima, Y. Udatsu, M. Okazawa, K. Sugimura, A. Tomoguni, M. Izukura; Rinku General Medical Center Izumisano Municipal Hospital, Izumisano City, Osaka Pref., Japan PURPOSE: For primary breast cancer, to measure the correct size and lesion with using 3D-US (ultrasound) and Contrast-US. Also to evaluate the safety and efficacy of radiofrequency ablation with overlapping technique for primary breast cancer. MATERIALS AND METHODS: Thirty two patients with Stage I, primary breast cancer, underwent with Overlapping radiofrequency ablation. it’s technique was completely cover the tumor by Cool-tip radiofrequency ablation system under 3D-US and Contrast-US. Overlapping is three steps: First, the center of tumor was ablated. Next is one tip of this tumor. At last, the other tip. Around the tumor, especially the front and the rear, we ablated 1cm margin. The follow-up examinations were performed by US, CT, and/or MRI dynamic study every 3 or 6 months. Therapeutic success was defined as a lack of contrast enhancement and non-viable cancer cells by core needle biopsy (CNB) and/or vacuum assisted biopsy (VAB). RESULTS: A total of 32 lesions underwent 161 radiofrequency ablation sessions (mean number, 4.2; range, 2-6) under general anesthesia. The mean intraoperative US tumor size was 1.7 cm (range, 1.1-2.0 cm). There was no major complication. The mean temperature in the ablated tumor lesion was 93 degree (range, 82-over 100 degree). All 32 lesions showed a lack of contrast enhancement and non-viable cells were seen by CNB and/or VAB. CONCLUSION: 3D-US and Contrast-US was very effective to measure the correct size and lesion of the primary breast cancer. Overlapping radiofrequency ablation technique is a safe and effective local treatment and seems to have potential to become an option as a minimally invasive therapy for S122

T1 breast cancer. Further study and follow-up are necessary to determined long-term oncological efficacy. Abstract No. 332 Unintended Thermal Injuries from RFA: Organ Protection with an Angioplasty Balloon Catheter in an Animal Model. M.-G. Knuttinen,1 T. Van Ha,2 C. Reilly,2 J. Bui,1 D. West,1 C. Owens,1 A. Montag,2 C. Straus;2 1University of Illinois, Chicago, IL; 2University of Chicago, Chicago, IL PURPOSE: To assess the feasibility and efficacy of balloon protection of adjacent organ in liver thermal ablation in a swine model. MATERIALS AND METHODS: Yorkshire-mix pigs were placed under general anesthesia. Using sonographic and fluoroscopic guidance, a balloon catheter was positioned between the liver and diaphragm or bowel. RFA was performed in the liver surface next to the protective inflated balloon. The pigs were immediately sacrificed and the organs were sectioned and inspected for thermal injury. RESULTS: 48 thermal lesions were created with the balloon protection. Additional 10 control lesions were made. Fewer diaphragm injuries were created when the RFA lesions were made with the interposed balloon catheter. Furthermore, less bowel injury was created when the balloon was used as a protective device between the bowel and nearby adjacent liver. CONCLUSION: Injury to nearby organs, such as diaphragm or bowel, is a possible drawback when percutaneous RFA is performed. We suggest a new technique in using a balloon catheter to protect organs during RFA procedures. Balloon protection appears to be efficacious in preventing injury to adjacent diaphragm or bowel in this swine model. Abstract No. 333 Evaluation of Irreversible Electroporation (IE) in a Swine Study: A New Non-Thermal Tumor Ablation Technique. E.W. Lee, J.D. Grant, C.T. Loh, S.T. Kee; UCLA Medical Center, Los Angeles, CA PURPOSE: 1. To determine the tissue-ablating effects of IE on swine liver. 2. To evaluate and correlate radiographic (MR, CT and US) and pathological findings of IE. MATERIALS AND METHODS: Upon ARC approval, 9 Yorkshire pigs underwent US-guided IE of the liver (90 pulses at 2000-3000 V/lesion), creating a total of 24 lesions and followed up for 24 hrs, 48 hrs or 14 days using US, MR and CT. The radiographic lesion sizes were compared with pathological findings. Immunostaining was used to evaluate the pathophysiology of IE induced-cell death and vascular effects. RESULTS: The mean maximum diameter of the lesions was 34.3 ⫾ 7.2 mm in 30.25 sec, (a total procedure time of 6.9 ⫾ 2.1 mins/lesion), with a mean difference of 1.0 ⫾ 3.6 mm between US and gross measurements (p⫽0.662). All 8 pigs tolerated the procedure well and survived for 24 or 48 hrs. One pig survived for 14 days: showing markedly smaller lesions on pathologic measurement (7.3 ⫾ 2.2 mm, p ⬍ 0.001). Contrast-enhanced CT showed well-marginated hypodensity with delayed peripheral enhancement in the ablated area. Vascular preservation is shown with a contrast-filled patent vessel in the middle of the lesion. On

MRI, the lesions were best visualized in T1W-VIBE or post-contrast and GRE sequences. DWI/ADC showed restricted diffusion in the lesions. A size difference of 1.4 ⫾ 4.5 mm (p⫽0.335) was found between MR/CT and gross measurement. H&E and Von Kossa staining showed complete cell death with a sharply demarcated margin between the ablated and non-ablated zone. Bile ducts and vessels were completely preserved. Focal hepatocellular regeneration was found in as early as 7 days post-IE. Areas of complete cell death stained nearly 100% with apoptotic markers (TUNEL, BCL-2, Caspase-3). Complete preservation of vessels were seen on vWf and VEGFR. No complications were noted peri- or post-procedure. CONCLUSION: 1. With real-time monitoring and wellcontrolled focused cell death of the target tissue, irreversible electroporation can be a novel and effective ablative method in hepatic tumor. 2. MRI, CT or US can be efficiently used for monitoring and characterization of IE ablated area perior immediately post-procedure.

Abstract No. 334 Safety and Therapeutic Effect of RFA Combined with TAE in Rabbit VX2 Liver Tumors. S. Li, R. Ni, L. Chen; First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China PURPOSE: To investigate safety and efficacy of radiofrequency ablation (RFA) combined with transcatheter artery embolization (TAE) on treatment of VX2 liver tumor of rabbit model. MATERIALS AND METHODS: Thirty six rabbits with implanted VX2 liver tumors were divided into 4 groups randomly. Group 1 served as control and received RFA only (n⫽9). Group 2, 3, and 4 received TAE and RFA (n⫽9 in each group). RFA was performed in day 1, 4, 7 after TAE respectively in study groups. Hepatic artery was embolized with lipiodol alone. Liver (ALT) and kidney (UREA) function of rabbit model were tested before procedure, 1, 4, and 7days after procedure respectively. 2, 2, and 5 rabbits were sacrificed for tumor harvest 1, 4, 7 days after RFA or TAE⫹RFA respectively. Maximal diameter of coagulation necrosis were recorded 7 days after study. Macroscopic and microscopic studies were also performed 1, 4, and 7days after.

CONCLUSION: RFA of VX2 liver tumor combined with TAE could evidently enlarge necrotic zone and may produce complete necrosis. However, RFA combined with TAE may impair liver function significantly when RFA

Abstract No. 335 CT Imaging of Ablation Zones after Radiofrequency Ablation (RFA) of Kidney Tumors. P.P. Sarlieve, J.R. Kachura; Toronto General Hospital and Mount Sinai Hospital, Toronto, ON, Canada PURPOSE: To determine the imaging features of ablation zones on triphasic CT scanning following RFA of kidney tumors. MATERIALS AND METHODS: All patients with kidney tumors treated with RFA at Toronto General Hospital and Mount Sinai Hospital since 2004, whose imaging follow-up consisted of triphasic CT scanning, were analyzed. Tumor pathology and size were noted. Typical CT follow-up was performed one month post-ablation and every 4-6 months thereafter. CT features evaluated included ablation zone size, attenuation, enhancement, and ancillary findings such as halo sign in perinephric fat. RESULTS: The patient cohort consisted of 33 patients (27 M, 6 F) with mean age 61 years (range 45-82). 37 tumors were treated, all using multi-tined LeVeen electrodes: 29 patients had a solitary tumor, whereas 4 patients had two tumors ablated each. Mean maximum tumor diameter was 2.3 cm (range 1.1-4.2). Pathological confirmation was obtained for 27 tumors (73%): there were 24 renal cell carcinomas and 3 oncocytic neoplasms. Mean CT imaging follow-up was 13 months (range 0.3-43). Ablation zone diameter was 10% larger than tumor diameter, on average, on the first follow-up CT, and then decreased to 7% smaller than the original tumor at 10 months and 19% smaller at 27 months post-ablation. Excluding 3 tumors containing calcifications, mean ablation zone attenuation was 40 ⫾ 15 Hounsfield Units (HU) at initial follow-up, and 27 ⫾ 7 HU at 33 months. One patient had obvious enhancing residual tumor tissue at initial follow-up which was successfully ablated with a second procedure. Another patient developed an enhancing nodule at the edge of the ablation zone at 35 months which was found to be chronic inflammation and fat necrosis on pathology. The halo sign, consisting of curvilinear soft tissue attenuation in perinephric fat, was noted around 16 ablation zones (43%), first identifed at a mean of 11 months post-ablation (range 5-13).

POSTER SESSIONS

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

performed within 4 days after TAE. Liver function impairment becomes less significant if RFA done 7 days after TAE. There was no obvious impact on renal function of in all groups.

CONCLUSION: After RFA of kidney tumors, ablation zones are initially larger than the treated tumors and then gradually decrease in size. The halo sign is a common delayed finding in perinephric fat post-ablation. Enhancing tissue related to the ablation zone may correspond to a non-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 thermochemical ablation in an ex-vivo pig liver model as a new method for tumor ablation. S123