Radiofrequency Ablation Zone Research Articles

Prospective Analysis of the Pattern and Risk for Severe Vital Sign Changes During Percutaneous Radiofrequency Ablation of the Liver Under Opioid Analgesia

The aims of this study were to evaluate the pattern of vital sign changes and to elucidate significant risk factors for severe cardiovascular inhibition caused by percutaneous hepatic radiofrequency ablation (RFA). A total of 102 patients (male-to-female ratio, 73:29; age range, 35-85 years; mean age, 58.1 years) with 119 malignant hepatic tumors were enrolled and analyzed prospectively. The patients underwent percutaneous RFA with IV infusion of opioid analgesics. Changes in blood pressure (BP) and heart rate (HR) and the occurrence of significant cardiovascular inhibition (BP or HR < 70% of baseline) were monitored during the procedure. Respiratory rate and skin body temperature were recorded before and after the procedure. Whereas the mean BP was elevated (36%, 43/119) or depressed (36%, 43/119) with a similar frequency, the HR was predominantly depressed (56%, 66/119) during the procedure. The BP and HR were stable in only 18% cases (21/119), respectively. The respiratory rate showed no significant change (p = 0.521) after RFA; however, body temperature decreased (p < 0.001) after RFA. Although significant cardiovascular inhibition occurred in 41 cases (35%), all of the cases could be managed successfully and the technical success rate was 100% (119/119). Among the risk factors analyzed, old age (B = -0.003, p = 0.019) was significant for systolic BP depression, and contact of the RFA zone with the central portal vein (B = -0.096, p = 0.014) and female sex (B = -0.078, p = 0.033) were significant risk factors for HR depression as determined by multivariate analysis. Changes in BP and HR, especially bradycardia, are common during percutaneous RFA of hepatic lesions. Significant risk factors for severe cardiovascular inhibition include contact of the RFA zone with the branches of the central portal vein, old age, and female sex.

Percutaneous Radiofrequency Ablation for Hepatic Tumors Abutting the Diaphragm: Clinical Assessment of the Heat-Sink Effect of Artificial Ascites

This study was designed to assess whether artificial ascites has a heat-sink effect on the ablation zone for percutaneous radiofrequency ablation (RFA) of hepatic tumors abutting the diaphragm. We retrospectively assessed 28 patients who underwent percutaneous RFA for the treatment of a single nodular hepatic tumor that abutted the diaphragm from July 2000 to December 2006. All patients underwent ultrasound-guided RFA using internally cooled electrodes. A single ablation for 12 minutes was applied using 3-cm active-tip electrodes. We divided patients into two groups on the basis of whether artificial ascites was introduced before RFA: Group A consisted of patients who received artificial ascites with a mean of 760 mL of a 5% dextrose in water solution (n = 15) and group B consisted of patients who did not receive artificial ascites (n = 13). The volume of the ablation zone was measured on CT images obtained immediately after the ablation procedure, and imaging findings were compared for both groups using the Student's t test. We also compared the local tumor progression rate between both groups using the chi-square test (mean follow-up, 37.4 months). There was no significant difference between the two patient groups with regard to age, sex, Child-Pugh class, or tumor location (p > 0.05). The tumors were significantly smaller in group A patients (mean +/- SD, 1.6 +/- 0.5 cm) than in group B patients (2.1 +/- 0.7 cm) (p = 0.019). The mean volume of the RFA zone was 31.6 +/- 11.9 cm(3) in group A patients and 30.9 +/- 11.0 cm(3) in group B patients. There was no significant difference between the groups in the ablation volume (p = 0.871). Local tumor progression was noted in four patients (26.7%) in group A and in three patients (23.1%) in group B. There was no significant difference in the local tumor progression rate between the two groups (p = 0.83). Artificial ascites did not show a heat-sink effect on the volume of the ablation zone after percutaneous RFA for the treatment of a hepatic tumor abutting the diaphragm.

Radiofrequency ablation using a new type of internally cooled electrode with an adjustable active tip: An experimental study in ex vivo bovine and in vivo porcine livers

Purpose The aims of this study were to evaluate the performance of radiofrequency (RF) ablation using a new type of internally cooled RF electrode with an adjustable active tip in an ex vivo bovine liver model and to determine if adjustment of the active tip length makes a significant difference in the size of ablation zone in an in vivo porcine liver model. Materials and methods We performed ex vivo experiments by producing 100 RF ablation zones in 40 extracted bovine livers using a new type of RF electrode that had an adjustable active tip (adjustable electrode) ( n = 50) and a conventional internally cooled electrode (conventional electrode) ( n = 50). We also performed an in vivo study with the induction of 30 RF ablation zones in ten living porcine livers using the adjustable electrode with 2 cm ( n = 15) and 3 cm ( n = 15) active tip adjustments. The size (three perpendicular diameters), volume and ratio of the two axes of the ablation zone were macroscopically evaluated and were compared. Results For the ex vivo study using a 2 cm and 3 cm active tip, there was no significant difference in ablation performance between the use of conventional and adjustable electrodes. For the use of the conventional and adjustable electrodes with 2 cm active tip, respectively, the volume was 10.75 ± 3.43 cm 3 versus 10.64 ± 3.25 cm 3 and the ratio of the two axes was 1.24 ± 0.16 versus 1.30 ± 0.17; p > 0.05. For the use of the conventional and adjustable electrodes with 3 cm active tip, respectively, the volume was 21.17 ± 4.09 cm 3 versus 21.48 ± 3.51 cm 3 and the ratio of the two axes was 1.28 ± 0.12 versus 1.28 ± 0.07; p > 0.05. For the in vivo study using the adjustable electrode, the ablation volume with the 2 cm adjustment was significantly smaller as compared to the 3 cm adjustment (5.29 ± 2.22 cm 3 versus 13.44 ± 4.25 cm 3; p < 0.05) with no statistical difference for the ratio of the two axes (1.44 ± 0.22 versus 1.49 ± 0.24; p > 0.05). Conclusion Using a new type of internally cooled RF electrode, we could induce different volumes of the RF ablation zone by means of adjusting the length of the exposed active tip, where performance was similar to the use of a conventional internally cooled RF electrode.

Ultrasonography-guided percutaneous radiofrequency ablation of hepatocellular carcinomas: A feasibility scoring system for planning sonography

Purpose This study was designed to evaluate whether a feasibility scoring system for planning sonography is a reliable predictor of a safe and complete ablation in ultrasonography (US)-guided percutaneous radiofrequency ablation (RFA) of hepatocellular carcinomas (HCCs). Materials and methods We retrospectively evaluated the therapeutic outcomes of 108 consecutive patients (M:F, 78:30; mean age, 57.4 years) with a single nodular HCC (mean diameter, 2.0 cm) treated by percutaneous RFA. All patients were assessed for the feasibility of performing an RFA at planning sonography prior to the ablation. The feasibility scoring system consisted of five categories: the safe electrode path (P); the vital organs adjacent to the RFA zone (O); tumor size (S); tumor conspicuity (C); and the heat-sink effect (H). Each category was divided into a four-point scale [1–4]. If a score of 4 in any category was determined, the patient was not considered to be a suitable candidate for percutaneous RFA. We assessed if the score of each category, safety score (P + O), and curability score (S + C + H) correlated with a safe and complete ablation using the chi-squared test and likelihood ratio test for trend. Results The technical success rate was 100% (108/108) based on CT images obtained immediately after ablation. There was no 30-day mortality after RFA. There were major complications (one case of severe vasovagal reflex, one case of hemoperitoneum and one case of a pseudoaneurysm) in three (2.7%) patients, and minor complications (one case of a biloma, one case of subsegmental infarction and one case of abscess) in three (2.7%) patients. Post-ablation syndrome as a side effect was noted in 38 (35.1%) of 108 patients. The primary technique effectiveness rate at 1 month was 95.1% (105/108). Local tumor progression was noted in eight (7.6%) of 105 patients during the follow-up period (range, 3.0–11.5 months; median, 5.8 months; mean, 5.7 months). There was no significant single category to predict complication and local tumor progression (Fisher's exact test, p > 0.05). Contrary to the safety score for the probability of complication ( p > 0.05), the curability score was significantly associated with the probability of local tumor progression (likelihood ratio test for trend; p = 0.03). Conclusion The new feasibility scoring system for planning US can be used as objective criteria to predict therapeutic efficacy rather than the safety of percutaneous RFA of an HCC.

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

ObjectiveThe 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 MethodsWe retrospectively assessed 45 patients with 46 HCCs (mean size, 2.2 cm) adjacent to the gallbladder (≤1.0 cm) treated with RF ablation using an internally cooled electrode system. An electrode was inserted into the tumor either parallel (n = 38) or perpendicular (n = 8) to the gallbladder wall. The safety and therapeutic efficacy of the procedures were assessed with clinical and imaging follow-up examinations. Follow-up with the use of CT ranged from four to 45 months (mean, 19 months). The association between variables (electrode direction, electrode type, tumor size, tumor location, lobar location) and the presence of a residual tumor or local tumor progression was also analyzed.ResultsThere were no major complications and minor complications were noted in three patients (7%) including one case of vasovagal syncope and two cases of bilomas. Wall thickening of the gallbladder adjacent to the RF ablation zone was noted in 14 patients (41%) as determined on immediate follow-up CT imaging. Wall thickening showed complete disappearance on subsequent follow-up CT imaging. The primary technique effectiveness rate was 96% (44/46) based on one-month follow-up CT imaging. Local tumor progression was noted in six (14%) of 44 completely ablated tumors during the follow-up period. The direction of electrode insertion (perpendicular), tumor size (≥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.ConclusionPercutaneous 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.

Effect of Artificial Ascites on Thermal Injury to the Diaphragm and Stomach in Radiofrequency Ablation of the Liver: Experimental Study with a Porcine Model

The purpose of this study was to evaluate the effect of artificial ascites on thermal injury to the diaphragm and stomach in a porcine model of radiofrequency ablation of the liver. We performed this study using eight pigs in experimental and control groups of four pigs each. Artificial ascites was produced before radiofrequency ablation to separate the liver from the diaphragm and the stomach in the experimental group. Using a 1-cm exposed internally cooled radiofrequency electrode for 5 minutes, we performed 74 hepatic ablations abutting the diaphragm and stomach. CT was performed on the day of the procedure and 7 days after ablation. The pigs were sacrificed, and necropsy was performed. We performed pathologic and CT examinations to compare the frequency and extent of thermal injury to the two organs. The mean number of radiofrequency ablations in each pig was 9.3 (range, 6-12). The mean number of ablation zones adjoining the diaphragm was 5.5 (range, 3-8) and of zones contiguous with the stomach was 3.8 (range, 3-4). Thermal injury to the adjacent organs occurred more frequently in the control group than in the experimental group (p < 0.05). The major complications of diaphragmatic hernia and gastric perforation occurred only in the control group. No major complications were identified in the experimental group at necropsy. The sizes of the radiofrequency ablation zone of the liver did not differ between the two groups (p > 0.05). The mean diameters of the diaphragmatic and gastric lesions did differ (p < 0.05). Histopathologic examination revealed a significant difference in the depths of thermal injury in the two groups (p < 0.05). Artificial ascites may be a simple and useful technique for reducing the frequency and severity of collateral thermal injury to the diaphragm and stomach during radiofrequency ablation of subcapsular hepatic tumors.

Radiofrequency ablation for hepatocellular carcinoma abutting the diaphragm: the value of artificial ascites

Ultrasound (US)-guided percutanoeus radiofrequency (RF) ablation is difficult to perform for treating a hepatic tumor abutting the diaphragm due to a poor sonic window and high risk of diaphragmatic thermal injury. RF ablation with assistance of the use of artificial ascites is a simple and safe technique for treating a hepatic dome tumor abutting the diaphragm. One can improve the sonic window and separate the RF ablation zone from the diaphragm by downward displacement of the liver with the use of a simple and inexpensive technique. Dextrose water solution is an ideal fluid due to its nonionic nature. Complications related to the use of artificial ascites including hemoperitoneum are rare. Peritoneal adhesion and tumor location in the bare area are the limitations for the application of this technique.

Percutaneous Radiofrequency Ablation with Artificial Ascites for Hepatocellular Carcinoma in the Hepatic Dome: Initial Experience

Our objective was to assess the feasibility, safety, and efficacy of percutaneous radiofrequency ablation with artificial ascites for hepatocellular carcinoma (HCC) in the hepatic dome. Sonographically guided percutaneous radiofrequency ablation with artificial ascites was performed in 25 patients with 34 HCCs using an internally cooled electrode radiofrequency system. At least one hepatic dome tumor in each patient was considered difficult to treat percutaneously because of partially visible tumor (n = 16) or poor electrode path (n = 9) on planning sonography. We artificially induced ascites before radiofrequency ablation by dripping 5% dextrose in water (D/W) solution to improve tumor visibility or electrode path and to separate the radiofrequency ablation zone from the diaphragm. We assessed the technical feasibility, safety, and efficacy of this technique with clinical and CT follow-up for at least 4 months (mean, 281.4 days) Artificial ascites was successfully achieved in 22 (88%) of 25 patients with the administration of a mean of 348 mL of D/W solution for an additional mean time of 9.3 minutes. There was substantial improvement in the visibility in 93.4% (15/16) of the partially visible tumors and in achieving a better path in 77.8% (7/9) of the tumors with a poor electrode path. The primary technique effectiveness rate for hepatic dome tumors was 96% (24/25) at 1-month follow-up CT. There was no diaphragmatic thermal injury in all but one case. No complication related to artificial ascites occurred during the follow-up period. Percutaneous radiofrequency ablation with artificial ascites appears a feasible, safe, and effective technique for treating HCC of the hepatic dome.

CT Findings after Radiofrequency Ablation in Rabbit Livers: Comparison of Internally Cooled Electrodes, Perfusion Electrodes, and Internally Cooled Perfusion Electrodes

To compare the computed tomography (CT) findings of radiofrequency (RF) ablation of rabbit livers with the use of internally cooled electrodes, perfusion electrodes, and internally cooled perfusion (ICP) electrodes. RF ablation zones were created in 24 rabbit livers in vivo in three groups, each treated at 30 W for 30 minutes with an electrode with a 1-cm active portion: one group was treated with an internally cooled electrode (group A), one with a perfusion electrode (group B), and one with an ICP electrode (group C). In the latter two groups, 0.9% saline solution mixed with contrast medium (9:1 ratio) was infused at a rate of 1 mL/min. Immediate CT images were ascertained in all groups and follow-up CT was performed in the latter two groups. CT findings of the RF ablation zone and surrounding liver parenchyma were evaluated and compared among groups. On immediate unenhanced CT, infused contrast medium was noted in the center of the ablation zone without extravasation. Marginal linear or tubular low densities of the RF ablation zone were noted only in groups B (n=4) and C (n=3). Liver infarction was more frequently noted in groups B (n=5) and C (n=7) than in group A (n=3). Periportal tracking was noted more frequently in groups B (n=7) and C (n=8) than in group A (n=1). Pericaval or perihepatic tracking was noted only in groups B (n=3) and C (n=3). Extensive portal venous gas was noted in one animal in group C. On CT, RF ablation with the perfusion or ICP electrode seemed to show more severe surrounding parenchymal changes than RF ablation with an internally cooled electrode.

Comparison of Lesion Conspicuity of Radiofrequency Ablation Zones among MR Sequences According to Time in the Normal Rabbit Liver

Purpose: To compare the lesion conspicuity of radiofrequency ablation (RFA) zones among MR sequences according to time in the normal rabbit liver. Materials and Methods: RFA zones were created in 12 rabbit livers with a 17-gauge internally cooled electrode (1-cm active tip, 30 Watts, 3 minutes). Three rabbits were sacrificed immediately, three days, two weeks, and six weeks after the RFA procedure, respectively. Before sacrifice, T1-, T2-weighted images (WI), and gadolinium-enhanced (GE)-T1WI images were obtained. The lesion conspicuity of the RFA zone and the contrast-to-noise ratio (CNR) of the RFA zone to the liver parenchyma were analyzed and compared among the MR sequences according to time. Results: On T1WI, the RFA zones were only clearly seen on acute phase. On T2WI, the RFA zones were clearly seen on all phases except the hyperacute phase. On GE T1WI, the RFA zones were clearly seen on all phases. The CNRs of the RFA zone to the liver parenchyma of GE-T1WI (8.1-12.4) were significantly higher than the CNRs of TIWI (1.6-2.7) and T2WI (1.7-6.3) on all phases (p

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 17gauge 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.

2013: Radiofrequency ablation with epinephrine injection: In Vivo study in a pig liver model

Objectives: To determine whether epinephrine injection prior to radiofrequency (RF) ablation can increase the extent of thermally mediated coagulation in in-vivo pig liver tissue.Methods: Eighteen RF ablation zones were created in six pigs with 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 RF ablation, the short-axis and long-axis diameters of the white zones in the gross specimens were compared.Results: Three RF ablations were technically unsuccessful. So, comparison was finally possible in 15 RF ablation zones. The mean short-axis and long-axis diameters of white zone of RF ablation after epinephrine injection (17.2 mm ± 1.8, 20.8 mm ± 3.7) were larger than RF ablation only (10 mm ± 1.2, 12.2 mm ± 1.1) and RF ablation after normal saline injection (12.8 mm ± 1.5, 15.6 mm ± 2.5) (p < .05).Conclusions: RF ablation with epinephrine injection can increase the diameter of the RF ablation zone of the liver and so it may be useful for treating larger lesions. Objectives: To determine whether epinephrine injection prior to radiofrequency (RF) ablation can increase the extent of thermally mediated coagulation in in-vivo pig liver tissue. Methods: Eighteen RF ablation zones were created in six pigs with 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 RF ablation, the short-axis and long-axis diameters of the white zones in the gross specimens were compared. Results: Three RF ablations were technically unsuccessful. So, comparison was finally possible in 15 RF ablation zones. The mean short-axis and long-axis diameters of white zone of RF ablation after epinephrine injection (17.2 mm ± 1.8, 20.8 mm ± 3.7) were larger than RF ablation only (10 mm ± 1.2, 12.2 mm ± 1.1) and RF ablation after normal saline injection (12.8 mm ± 1.5, 15.6 mm ± 2.5) (p < .05). Conclusions: RF ablation with epinephrine injection can increase the diameter of the RF ablation zone of the liver and so it may be useful for treating larger lesions.