Silver Nanofunctionalized Stent after Radiofrequency Ablation Suppresses Tissue Hyperplasia and Bacterial Growth.

Intraductal radiofrequency (RF) ablation combined with placement of a self-expandable metal stent (SEMS) for malignant biliary obstruction has risks such as stent- and heat-induced biliary sludge and restenosis. Here, we investigated the efficacy of a silver nanoparticles (AgNPs)-coated SEMS to inhibit tissue hyperplasia and bacterial growth caused by RF ablation with stent placement in the rabbit bile duct. The release behavior and antibacterial effects of AgNPs-coated SEMSs were evaluated. Then, SEMSs were successfully placed in all rabbits immediately after RF ablation. Ag ions were rapidly released at the beginning and then showed a gradual release behavior. The AgNPs-coated SEMS significantly inhibited bacterial activity compared to the uncoated SEMS (p < 0.05). Cholangiography and histological examination confirmed that the level of tissue hyperplasia was significantly lower in the AgNPs group than in the control group (all p < 0.05). Immunohistochemistry analyses revealed that TUNEL-, HSP 70-, and α-SMA-positive areas were significantly lower in the AgNPs group than in the control group (all p < 0.05). Intraductal RF ablation combined with nanofunctionalized stent placement represents a promising new approach for suppressing thermal damage as well as stent-induced tissue hyperplasia and bacterial growth.

Assessment of an ECG-Based System for Localizing Ventricular Arrhythmias in Patients With Structural Heart Disease.

Background We have previously developed an intraprocedural automatic arrhythmia-origin localization (AAOL) system to identify idiopathic ventricular arrhythmia origins in real time using a 3-lead ECG. The objective was to assess the localization accuracy of ventricular tachycardia (VT) exit and premature ventricular contraction (PVC) origin sites in patients with structural heart disease using the AAOL system. Methods and Results In retrospective and prospective case series studies, a total of 42 patients who underwent VT/PVC ablation in the setting of structural heart disease were recruited at 2 different centers. The AAOL system combines 120-ms QRS integrals of 3 leads (III, V2, V6) with pace mapping to predict VT exit/PVC origin site and projects that site onto the patient-specific electroanatomic mapping surface. VT exit/PVC origin sites were clinically identified by activation mapping and/or pace mapping. The localization error of the VT exit/PVC origin site was assessed by the distance between the clinically identified site and the estimated site. In the retrospective study of 19 patients with structural heart disease, the AAOL system achieved a mean localization accuracy of 6.5±2.6 mm for 25 induced VTs. In the prospective study with 23 patients, mean localization accuracy was 5.9±2.6 mm for 26 VT exit and PVC origin sites. There was no difference in mean localization error in epicardial sites compared with endocardial sites using the AAOL system (6.0 versus 5.8 mm, P=0.895). Conclusions The AAOL system achieved accurate localization of VT exit/PVC origin sites in patients with structural heart disease; its performance is superior to current systems, and thus, it promises to have potential clinical utility.

Feasibility study shows concordance between image-based virtual-heart ablation targets and predicted ECG-based arrhythmia exit-sites.

INTRODUCTION: We recently developed two noninvasive methodologies to help guide VT ablation: population-derived automated VT exit localization (PAVEL) and virtual-heart arrhythmia ablation targeting (VAAT). We hypothesized that while very different in their nature, limitations, and type of ablation targets (substrate-based vs. clinical VT), the image-based VAAT and the ECG-based PAVEL technologies would be spatially concordant in their predictions. OBJECTIVE: The objective is to test this hypothesis in ischemic cardiomyopathy patients in a retrospective feasibility study. METHODS: Four post-infarct patients who underwent LV VT ablation and had pre-procedural LGE-CMRs were enrolled. Virtual hearts with patient-specific scar and border zone identified potential VTs and ablation targets. Patient-specific PAVEL based on a population-derived statistical method localized VT exit sites onto a patient-specific 238-triangle LV endocardial surface. RESULTS: Ten induced VTs were analyzed and 9-exit sites were localized by PAVEL onto the patient-specific LV endocardial surface. All nine predicted VT exit sites were in the scar border zone defined by voltage mapping and spatially correlated with successful clinical lesions. There were 2.3 ± 1.9 VTs per patient in the models. All five VAAT lesions fell within regions ablated clinically. VAAT targets correlated well with 6 PAVEL-predicted VT exit sites. The distance between the center of the predicted VT-exit-site triangle and nearest corresponding VAAT ablation lesion was 10.7 ± 7.3 mm. CONCLUSIONS: VAAT targets are concordant with the patient-specific PAVEL-predicted VT exit sites. These findings support investigation into combining these two complementary technologies as a noninvasive, clinical tool for targeting clinically induced VTs and regions likely to harbor potential VTs.

Comparing rates of atrioesophageal fistula with contact force-sensing and non-contact force-sensing catheters: analysis of post-market safety surveillance data.

PURPOSE: There is limited data on the specific incidence of serious adverse events, such as atrioesophageal fistula (AEF), associated with either contact force (CF) or non-CF ablation catheters. Since the actual number of procedures performed with each type of catheter is unknown, making direct comparisons is difficult. The purpose of this study was to assess the incidence of AEF associated with the use of CF and non-CF catheters. Additionally, we aimed to understand the workflow present in confirmed AEF cases voluntarily provided by physicians. METHODS: The number of AEFs for 2014-2017 associated with each type of catheter was extracted from an ablation device manufacturer's complaint database. Proprietary device sales data, a proxy for the total number of procedures, were used as the denominator to calculate the incidence rates. Additional survey and workflow data were systematically reviewed. RESULTS: Both CF and non-CF ablation catheters have comparably low incidence of AEF (0.006 ± 0.003% and 0.005 ± 0.003%, respectively, p = 0.69). CF catheters are the catheter of choice for left atrium (LA) procedures which pose the greatest risk for AEF injury. Retrospective analysis of seven AEF cases demonstrated that high power and force and long RF duration were delivered on the posterior wall of the left atrium in all cases. CONCLUSIONS: CF and non-CF ablation catheters were found to have similar AEF incidence, despite CF catheters being the catheter of choice for LA procedures. More investigation is needed to understand the range of parameters which may create risk for AEF.

Various complications of percutaneous radiofrequency ablation for hepatic tumors: radiologic findings and technical tips.

Radiofrequency ablation is a safe and effective treatment for primary and secondary liver malignancies and has a low complication rate; however, there are various radiofrequency ablation-related complications which can occur from the thorax to the pelvis. Although most of these complications are usually minor and self-limited, they may become fatal if diagnosis and treatment are delayed. It is important for radiologists performing radiofrequency ablation to have a perspective regarding the possible radiofrequency ablation-related complications and their risk factors as well as the radiologic findings for their timely detection and increase of the treatment efficacy, and thereby encouraging the use of the radiofrequency ablation technique. This article illustrates the various imaging features of common and rare radiofrequency ablation-related complications as well as offers technical tips in order to avoid these complications.

Assessment of Therapeutic Response of Ablated Lesion after Radiofrequency Ablation in Patients with Unresectable Lung Malignancies by Multiphase Contrast-enhanced MRI

PURPOSE: We evaluated which phase was important to recognize local progression of an ablated zone after RFA on multiphase contrast-enhanced MRI (CE-MRI) in patients with unresectable lung malignancy. MATERIALS AND METHODS: Twenty patients who had unresectable lung malignancy underwent multiphase CE-MRI examinations immediately after RFA. We evaluated the enhancement patterns of the ablated zone on multiphase CE-MRI: type I, no enhancement of the ablated zone; type II, enhancement of the ablated margin; type III, heterogeneous enhancement of the ablated zone. We evaluated the association enhancement type with local progression of the ablated zone on the follow up CT using Spearman's ranked test. RESULTS: In complete ablation, the enhancement pattern was types I (11.1%) or II (88.9%). In unsuccessfully treated, type II (57.1%) or III (42.9%) pattern observed in the arterial phase. However, types II (21.4%) and III (78.6%) observed in the venous, and types II (7.1%) and III (92.9%) observed equilibrium phases. Local progression of the ablated zone was associated with the enhancement pattern in equilibrium phases (r=0.8, p < .05). CONCLUSION: Equilibrium phases on multiphase CE-MRI might play a more important role in evaluating an ablated zone for predicting local recurrence after RFA.

Percutaneous radiofrequency ablation of hepatocellular carcinomas adjacent to the gallbladder with internally cooled electrodes: assessment of safety and therapeutic efficacy.

OBJECTIVE: The objective of this study was to evaluate the safety and therapeutic efficacy of percutaneous radiofrequency (RF) ablation for the treatment of hepatocellular carcinomas (HCCs) adjacent to the gallbladder with the use of internally cooled electrodes. MATERIALS AND METHODS: We retrospectively assessed 45 patients with 46 HCCs (mean size, 2.2 cm) adjacent to the gallbladder (or=3 cm) and tumor location (a tumor that abutted the gallbladder) were associated with an increased risk of early incomplete treatment. No variable was significantly associated with local tumor progression. CONCLUSION: Percutaneous RF ablation of HCCs adjacent to the gallbladder using an internally cooled electrode is a safe and effective treatment. Significant risk factors that lead to early incomplete treatment include tumor size, tumor location and electrode direction.

Does Artificial Ascites Induce the Heat-Sink Phenomenon during Percutaneous Radiofrequency Ablation of the Hepatic Subcapsular Area?: an in vivo Experimental Study Using a Rabbit Model

OBJECTIVE: To evaluate the effect of the heat-sink phenomenon induced by artificial ascites on the size of the ablation zone during percutaneous radiofrequency (RF) ablation of the hepatic subcapsular area in an in vivo rabbit model. MATERIALS AND METHODS: A total of 21 percutaneous rabbit liver RF ablations were performed with and without artificial ascites (5% dextrose aqueous solution). The rabbits were divided into three groups: a) control group (C, n = 7); b) room temperature ascites group (R, n = 7); and c) warmed ascites group (W, n = 7). The tip of a 1 cm, internally cooled electrode was placed on the subcapsular region of the hepatic dome via ultrasound guidance, and ablation was continued for 6 min. Changes in temperature of the ascites were monitored during the ablation. The size of the ablation zones of the excised livers and immediate complications rates were compared statistically between the groups (Mann-Whitney U test, Kruskal-Wallis test, linear-by-linear association, p = 0.05). RESULTS: One rabbit from the "W" group expired during the procedure. In all groups, the ascites temperatures approached their respective body temperatures as the ablations continued; however, a significant difference in ascites temperature was found between groups "W" and "R" throughout the procedures (39.2 +/- 0.4 degrees C in group W and 33.4 +/- 4.3 degrees C in group R at 6 min, p = 0.003). No significant difference was found between the size of the ablation zones (782.4 +/- 237.3 mL in group C, 1,172.0 +/- 468.9 mL in group R, and 1,030.6 +/- 665.1 mL in group W, p = 0.170) for the excised liver specimens. Diaphragmatic injury was identified in three of seven cases (42.9%) upon visual inspection of group "C" rabbits (p = 0.030). CONCLUSION: Artificial ascites are not likely to cause a significant heat-sink phenomenon in the percutaneous RF ablation of the hepatic subcapsular region.

Percutaneous Radiofrequency Ablation of Hepatocellular Carcinomas Adjacent to the Gallbladder with Internally Cooled Electrodes: Assessment of Safety and Therapeutic Efficacy

OBJECTIVE: The objective of this study was to evaluate the safety and therapeutic efficacy of percutaneous radiofrequency (RF) ablation for the treatment of hepatocellular carcinomas (HCCs) adjacent to the gallbladder with the use of internally cooled electrodes. MATERIALS AND METHODS:We retrospectively assessed 45 patients with 46 HCCs (mean size, 2.2 cm) adjacent to the gallbladder ( or =3 cm) and tumor location (a tumor that abutted the gallbladder) were associated with an increased risk of early incomplete treatment. No variable was significantly associated with local tumor progression. CONCLUSION: Percutaneous RF ablation of HCCs adjacent to the gallbladder using an internally cooled electrode is a safe and effective treatment. Significant risk factors that lead to early incomplete treatment include tumor size, tumor location and electrode direction.

Radiofrequency Ablation Using a Monopolar Wet Electrode for the Treatment of Inoperable Non-Small Cell Lung Cancer: a Preliminary Report

OBJECTIVE: To assess the technical feasibility and complications of radiofrequency ablation (RFA) using a monopolar wet electrode for the treatment of inoperable non-small cell lung malignancies. MATERIALS AND METHODS: Sixteen patients with a non-small cell lung malignancy underwent RFA under CT guidance. All the patients were non-surgical candidates, with mean maximum tumor diameters ranging from 3 to 6 cm (mean: 4.6 +/- 1.1 cm). A single 16-gauge open-perfused electrode with a 2 cm exposed tip was used for the procedure. A 0.9% NaCl saline solution was used as the perfusion liquid with the flow adjusted to 30 mL/h. The radiofrequency energy was applied for 10-40 minutes. The response to RFA was evaluated by performing contrast-enhanced CT immediately after RFA, one month after treatment and then every three months thereafter. RESULTS: Technical failure was observed in six (37.5%) of 16 patients: intractable pain (n = 2) and non-stop coughing (n = 4). The mean follow-up interval was 15 +/- 8 months (range: 9-31 months). The mean maximum ablated diameter in the technically successful group of patients ranged from 3.5 to 7.5 cm (mean 5.1 +/- 1.3 cm). Complete necrosis was attained for eight (80%) of 10 lesions, and partial necrosis was achieved for two lesions. There were two major complications (2/10, 20%) encountered: a hemothorax (n = 1) and a bronchopleural fistula (n = 1). CONCLUSION: Although RFA using a monopolar wet electrode can create a large ablation zone, it is associated with a high rate of technical failure when used to treat inoperable non-small cell lung malignancies.

Radiofrequency Ablation with Epinephrine Injection: In Vivo Study in Normal Pig Livers

PURPOSE: We wanted to evaluate whether epinephrine injection prior to radiofrequency (RF) ablation can increase the extent of thermally mediated coagulation in vivo normal pig liver tissue. MATERIALS AND METHODS: Eighteen RF ablation zones were created in six pigs using a 17-gauge internally cooled electrode under ultrasound guidance. Three RF ablation zones were created in each pig under three conditions: RF ablation alone, RF ablation after the injection of 3 mL of normal saline, and RF ablation after the injection of 3 mL of epinephrine (1:10,000 solution). After the RF ablation, we measured the short and long diameters of the white zones in the gross specimens. RESULTS: Three of the RF ablations were technically unsuccessful; therefore, measurement of white zone was finally done in 15 RF ablation zones. The mean short and long diameters of the white zone of the RF ablation after epinephrine injection (17.2 mm +/- 1.8 and 20.8 mm +/- 3.7, respectively) were larger than those of RF ablation only (10 mm +/- 1.2 and 12.2 mm +/- 1.1, respectively) and RF ablation after normal saline injection (12.8 mm +/- 1.5 and 15.6 mm +/- 2.5, respectively) (p < .05). CONCLUSION: RF ablation with epinephrine injection can increase the diameter of the RF ablation zone in normal pig liver tissue.

Complications Following Radiofrequency Ablation of the Porcine Liver through Portal Vein Penetration: Radiological Findings

PURPOSE: To evaluate complications after radiofrequency ablation (RFA) of the porcine liver through portal vein penetration. MATERIALS AND METHODS: Twelve pigs were divided into two groups. In group I (n=11) animals, the portal veins were directly penetrated with an electrode, and in the group II (n=16) animals, the portal veins were located within the expected ablation area. For the group I pigs, RFA were performed for seven minutes after complete portal vein passing of the exposed tip. Gray-scale and Doppler ultrasonography, and CT were performed before and after RFA on the procedure day, and on day two. If any complications were found, the same studies were performed at day seven. We analyzed the presence and extent of thrombotic occlusion, the vascular stricture, the arterioportal shunt, and the presence of an intra-abdominal hemorrhage. We applied Fisher's exact test to compare the complication rate between the two groups;, a value was considered statistically significant if the p-value was less than 0.05. RESULTS: In the group I animals (n=11), three had complete thrombotic occlusion of the portal vein. Among these three animals,, one had a segmental infarction, and one animal showed a partial occlusion. In the group II animals (n=16), complications were not identified. Statistical analysis revealed the complication rate of group I was significantly higher than that of group II (p=.019). CONCLUSION: The portal vein occlusion rate was significantly higher in the portal vein penetrating group than in the non-penetrating group.

A Metastatic Adrenal Tumor from a Hepatocellular Carcinoma: Combination Therapy with Transarterial Chemoembolization and Radiofrequency Ablation

The adrenal gland is the second most common site of metastasis from a hepatocellular carcinoma (HCC). Radiofrequency ablation (RFA) for these tumors has been reported to be a potentially effective alternative to an adrenalectomy, especially for inoperable patients. However, for intermediate or large adrenal tumors, combination therapy of transarterial chemoembolization (TACE) and RFA can be attempted as it may reduce the heat sink effect. A 74-year-old patient presented with abdominal discomfort. Abdominal CT images revealed a 5.0 cm sized right adrenal mass. A percutaneous biopsy of the adrenal mass revealed a metastatic hepatocellular carcinoma. TACE was performed on the adrenal mass. However, a one-month follow-up CT image revealed a residual viable tumor. RFA was performed for the adrenal tumor six weeks after the TACE. No procedure-related major complications were noted. The serum alpha-fetoprotein level had also been normalized after the treatment, and 10-month follow-up CT images showed no definite evidence of viable adrenal tumor.

Comparison of Radiofrequency Ablation Lesion Size with Occlusion of Renal Vessels in Rabbit Kidneys: Occlusion of Renal Artery, Vein, and Both Vessels

PURPOSE: The purpose of this study was to compare the in-vivo efficiency of vascular occlusion on radiofrequency ablation (RFA) lesion size in a rabbit kidney model. MATERIALS AND METHODS: RFA lesions were created in a single kidney in 20 rabbits using an internally cooled electrode. Twenty ablation zones (1 per kidney) were created using 4 different regimens: RFA without vascular occlusion (n = 5), RFA with renal artery occlusion (n = 5), RFA with renal vein occlusion (n = 5), RFA with renal artery and vein occlusion (n = 5). Seven days later, the rabbits were sacrificed and the lesions were excised. These groups were then compared with respect to the dimensions of the ablation zones and the changes in impedance and current during RFA. RESULTS: The maximum ablation zone width was the greatest in the renal artery and vein occlusion group (21.0+/-1.4 mm), followed by the renal artery occlusion group (17.8+/-1.0 mm), the renal vein occlusion group (17.4+/-1.1 mm), and the nonocclusion group (7.8+/-2.4 mm) (p < 0.05). No significant differences were observed for impedances and currents between the 4 groups. CONCLUSION: Vascular occlusion combined with RFA effectively increased ablation zone dimensions compared with RFA alone, and the best effect was accomplished by combined renal artery and vein occlusion.

Ferucarbotran-Enhanced MR Imaging of the Radiofrequency Ablation Zones in the Normal Rabbit Liver: Comparison with the Conventional MR Imaging

PURPOSE: We wanted to evaluate the findings of ferucarbotran-enhanced MR imaging of the radiofrequency (RF) ablation zones in normal rabbit livers and we compared the findings with the conventional MR imaging. MATERIALS AND METHODS: RF ablation zones were created in the livers of 12 rabbits in vivo by using a 17-gauge internally cooled electrode with 1-cm active tip, and RF energy (maximum power: 30 Watt) was applied for three minutes. Three rabbits were sacrificed immediately and then at three days, two weeks and six weeks after RF ablation. Before sacrifice, the T1- and T2-weighted images (WI) and the ferucarbotran-enhanced T2*WIs were obtained and compared regarding the signal intensity of ablation zone, the laminar pattern of the signal intensity and the contrast-to-noise ratio (CNR) of the ablation zone to the liver parenchyma. RESULTS: On T1- and T2WIs, the RF ablation zones showed two to four laminar patterns of signal intensity according to the time. Meanwhile, on the ferucarbotran-enhanced T2WIs, the RF ablation zones showed high signal intensity without a laminar pattern regardless of time. The CNRs of the ablation zones to the liver parenchyma on the ferucarbotran-enhanced T2*WIs (18.2+/-5.9) were significantly higher than those of the TIWIs (1.6+/-1.5) and T2WIs (2.7+/-1.9) (p < 0.05). CONCLUSION: On the ferucarbotran-enhanced T2*WI, the RF ablation zones showed high signal intensity without a distinct laminar pattern and significantly higher lesion conspicuity than did the conventional T1- and T2WIs. Therefore, the ferucarbotran-enhanced T2*WI shows the RF ablation zone more accurately and clearly than do the conventional T1- and T2WIs.

Radiofrequency Neurotomy of the Medial Branch for the Management of Lumbar Zygapophysial Joint Pain

PURPOSE: We wanted to investigate the efficacy of percutaneous radiofrequency (RF) neurotomy of the medial branch for the management of chronic low back pain due to lumbar zygapophysial joint dysfunction. MATERIALS AND METHODS: Thirteen patients who had unremitting chronic low back pain for more than 6 months and whose VAS scores were over 7 were selected on the basis of double comparative nerve blocks. The patients consist of three males and 10 females, and their nean age was 67 years. Sensory stimulation was performed to detect the "pathologic branches" that were responsible for pain generation. RF neurotomy was performed using a lesion generator at 80 C for 90 seconds. The postoperative outcome was classified, depending on the degree of pain reduction, as excellent (> or = 75%), good (50-75%), and poor (<50%). Follow-up evaluation was performed at 6 weeks, 3 months and 6 months after surgery. RESULTS: The mean number of medial branches was 6.2. Eleven patients had bilateral disease and two had unilateral disease. Sensory stimulation was positive in all patients with a mean amplitude of 4.5V (range: 0.15-6 V). The L5 dorsal ramus was the most frequently involved segment, and this was followed by L4, L3 and L2. The number of lesionings for each medial branch was 3.7. The surgical outcome was graded as excellent (53%), good (23%), and poor (24%) after 6 months of follow-up. Transient backaches were noticed in two patients; however, complications were not observed. Recurrences were not demonstrated during the follow-up period CONCLUSION: We conclude that RF neurotomy of the medial branches is an efficient method to substantially alleviate the chronic low back pain caused by zygapophysial joint dysfunction.

Radiofrequency Ablation of Hepatic Cysts: Case Report

Radiofrequency ablation has been frequently performed on intra-hepatic solid tumor, namaly, hepatocellular carcinoma, metastatic tumor and cholangiocarcinoma, for take the cure. But, the reports of radiofrequency ablation for intrahepatic simple cysts are few. In vitro experiment of animal and in vivo treatment for intrahepatic cysts of human had been reported in rare cases. We report 4 cases of radiofrequency ablation for symptomatic intrahepatic cysts.

Combined Radiofrequency Ablation and Acetic Acid Hypertonic Saline Solution Instillation: An In Vivo Study of Rabbit Liver

OBJECTIVE: We wanted to determine whether combined radiofrequency ablation (RFA) and acetic acid-hypertonic saline solution (AHS) instillation can increase the extent of thermally mediated coagulation in in vivo rabbit liver tissue. We also wished to determine the optimal concentration of the solution in order to maximize its effect on extent of the RFA-induced coagulation. MAERIALS AND METHODS: Forty thermal ablation zones were produced in 40 rabbits by using a 17-gauge internally cooled electrode with a 1-cm active tip under ultrasound guidance. The rabbits were assigned to one of four groups: group A: RFA alone (n=10) ; group B: RFA with 50% AHS instillation (n=10) ; group C: RFA with 25% AHS instillation (n=10) ; group D: RFA with 15% AHS instillation (n=10). A range of acetic acid concentrations diluted in 36% NaCl to a total volume of 1 mL were instilled into the liver before RFA. The RF energy (30 W) was applied for three minutes. After RFA, in each group, the maximum diameters of the thermal ablation zones in the gross specimens were compared. Technical success and the complications that arose were evaluated by CT and on the basis of autopsy findings. RESULTS: All procedures are technically successful. There were six procedure-related complications (6/40; 15%) : two localized perihepatic hematomas and four chemical peritonitis. The incidence of chemical peritonitis was highest for group B with the 50% AHS solution instillation (30%). With instillation of 15% AHS solution, a marked decrease of tissue impedance (24.5+/-15.6 omega) and an increase of current (250 mA) occurred as compared to RFA alone. With instillation of the solutions before RFA (group B, C and D), this produced a greater mean diameter of coagulation necrosis than the diameters for rabbits not instilled with the solution (group A) (p < 0.05). However, there was no significant difference between group B, C, and D. CONCLUSION: Combined AHS instillation and RFA can increase the dimension of coagulation necrosis in the liver with a single application. A low concentration of AHS (15%) showed similar effects in increasing the extent of RF-induced coagulation, but there were less side effects as compared to the high concentration of AHS.

Radio-frequency Ablation in Patients with Malignant Hepatic Tumor and Experimental Model: Comparison of Expandable Needle and Water-Cooled Needle

PURPOSE: The purpose of this study was to compare the shape and volume of the radio-frequency induced lesions produced by two commercially available radio-frequency ablation (RFA) systems, the expandable and cooled-tip needles, in clinical patients and an experimental model. MATERIALS AND METHODS: A twelve-array anchor expandable needle electrode and a single cooled-tip needle electrode were used to treat hepatic tumors with a single session in 23 patients (20 hepatocellular carcinomas and 3 hepatic metastases) and fourteen patients (10 hepatocellular carcinomas and 4 hepatic metastases), respectively. Twenty RFA induced lesions were created with each system in 10 explanted bovine livers. The shape of the RFA induced lesions were divided into oval lesions along or perpendicular to the axis of the electrode and spherical lesions, and we then calculated the volumes of the RFA induced lesions. RESULTS: Fourteen (61%) lesions of the 23 patients treated with the expandable system were oval perpendicular to the axis of the electrode and nine (39%) of the lesions were spherical. All the lesions (100%) of the 14 patients treated with the cooled-tip needle were oval along the axis of the electrode. In the ex vivo bovine livers, the shape of the all RFA induced lesions was oval perpendicular to the axis of the electrode for the expandable needle, and oval along the axis of the electrode for the cooled-tip needle. The mean diameter and volume of the RFA induced lesions in the patients were 3.35+/-0.56cm and 19.9+/-6.53 cm3, respectively, for the expandable needle and 3.58+/-0.78 cm and 23.19+/-5.27 cm3, respectively, for the cooled-tip needle. In the ex vivo model, the mean diameter and volume of RFA induced lesions were 3.41+/-0.59 cm and 26.59+/-8.02 cm3, respectively, for the expandable needle, and 4.04+/-0.65 cm and 33.82+/-6.16 cm3, respectively, for the cooled-tip needle (p<0.05). CONCLUSION:These results indicate that the shape of RFA induced lesions with the expandable needle were oval perpendicular to the axis of the electrode but those with the cooled-tip needle were oval along the axis of the electrode in both the clinical and experimental models. The cooled-tip needle induced significantly larger lesions than the expandable needle in the clinical patients and the experimental model. We need to consider these characteristic findings for RFA when we are performing such procedures.