Radiofrequency Ablation Volume Research Articles

Ablative Volume of Radiofrequency Ablation Related to Intrahepatic Recurrence-Free Survival of Hepatocellular Carcinoma

Abstract Purpose The aim of this study was to evaluate intrahepatic recurrence-free survival of hepatocellular carcinoma (HCC) after Radiofrequency ablation (RFA) Methods A retrospective cohort study of single HCC treated by RFA between 2015 and 2017. Fifty patients were enrolled in the study. Tumor volume and ablative volume were measured by using Syngo.via application (Siemen Healthineers, United States). Ablative volume classified into small and large ablative volumes. Ablative margin was evaluated by visual comparison between pre- and post-RFA images and classified into two groups: closed ablative margin (<0.5cm) and large ablative margin (>0.5 cm). The recurrence tumor was classified as local tumor progression (LTP) and intrahepatic distant recurrence (IDR). The recurrence-free survival rate and independent risk for tumor recurrence were analyzed. Results Recurrence-free survival rate at the first, second, third, and fourth year after RFA was 83, 56, 44, and 44%, respectively. The average recurrence-free survival time in large ablative volume group was significantly longer than small ablative volume group (31.57 vs. 8.50 months, p = 0.003). A significant independent risk factor for tumor recurrence was large ablative volume (hazard ratio = 0.12, 95% confidence interval = 0.02–0.84, p = 0.033). The IDR group had ratio of actual ablative volume by ideal ablative volume (ablative ratio) higher than LTP group and nonrecurrent group. Conclusion The large ablative volume prevented tumor recurrence and increased recurrence-free survival rate. But aggressive ablation with high ablative volume ratio could increase risk of IDR.

Computational Modeling of Cardiac Ablation Incorporating Electrothermomechanical Interactions

AbstractThe application of radio frequency ablation (RFA) has been widely explored in treating various types of cardiac arrhythmias. Computational modeling provides a safe and viable alternative to ex vivo and in vivo experimental studies for quantifying the effects of different variables efficiently and reliably, apart from providing a priori estimates of the ablation volume attained during cardiac ablation procedures. In this contribution, we report a fully coupled electrothermomechanical model for a more accurate prediction of the treatment outcomes during the radio frequency cardiac ablation. A numerical model comprising of cardiac tissue and the cardiac chamber has been developed in which an electrode has been inserted perpendicular to the cardiac tissue to simulate actual clinical procedures. Temperature-dependent heat capacity, electrical and thermal conductivities, and blood perfusion rate have been considered to model more realistic scenarios. The effects of blood flow and contact force of the electrode tip on the treatment outcomes of a fully coupled model of RFA have been systematically investigated. The numerical study demonstrates that the predicted ablation volume of RFA is significantly dependent on the blood flow rate in the cardiac chamber and also on the tissue deformation induced due to electrode insertion depth of 1.5 mm or higher.

Single Day Observational Experience at High Volume Ablation Programs: What is the Impact to Practicing Electrophysiologists?

Significant improvements in catheter technology, electro-anatomic (EA) mapping and techniques to reduce fluoroscopy during radiofrequency ablation (RFA) of atrial fibrillation (AF) are on-going.However, few educational opportunities are available post fellowship for Electrophysiologists (EPs) to understand and integrate them into their practice, preventing wide spread adoption. The impact of observational learning for adoption of new technologies and techniques in the field of cardiac electrophysiology has not been studied. We sought to report the impact of a visit to a high-volume center with experience in new technologies and fluoroscopy reductionto the clinical practice of EPs. Between 8/2014 and 10/2017 a total of 150 EPs visited 3 hospitals that perform a high volume of AF RFAs. EPs observed a minimum of 4 RFAs, primarily AF. AF RFAs were performed without fluoroscopy, using Carto 3 Version 4 (Biosense Webster) and intracardiac Echocardiography. There was ample interaction and discussion between hosting and visiting EP. 73 EPs (48.6% of visitors) completed an electronic survey after the visit. The majority reported a significant reduction in fluoroscopy (>50%) and procedure (>20%).68% adopted a rigorous workflow and reported an increase in their confidence level with intracardiac echo (79%), continuous mapping (52%) and the Visitag module (61%). Observational experience can have an immense impact on the clinical practice of EPs. Further effort should be devoted to such programs and to study in a more systematic way their ultimate impact on patient care.

Tactics of treatment of varicose disease, complicated by thrombosis, using miniinvasive methods

Objective. To determine the treatment tactics for varicose dilation of veins, complicated by thrombosis of subcutaneous veins and the shin deep veins, using miniinvasive methods.
 Маterals and methods. The results of treatment in the IGUS named after V. Т. Zaytsev NAMS of Ukraine in 2015 - 2017 yrs of 80 patients, suffering varicothrombophlebitis, were analyzed. The patients were divided into two groups. In Group I 38 patients, suffering varicothrombophlebitis and/or the shin deep vein thrombosis (DVT), were included, who were treated in accordance to the algorithm proposed. In Group II 42 patients with the same pathology were included, to them a standard treatment was conducted.
 Results. Immediately after the operation in the Group I patients a severe morbidity, connected with the operation technique (DVT, pulmonary thromboembolism, hemorrhage) were absent. Rate of cutaneous neurological disorders in distal parts of the extremities in patients, to whom endovenous laser coagulation was performed, have constituted 5.2%, and in radiofrequency ablation (RFA) – 2.6%. Due to differentiated approach applied for determination of the operative intervention volume for varicose dilation of veins, complicated by varicothrombophlebitis and/or DVTH of the shin, it became possible to perform operative intervention of lesser traumaticity and to achieve good immediate result in majority of the patients.
 In Group II in 1 patient postoperative period have complicated by DVT. Of the local complications lymphorrhea was observed in 5% patients, and in 2 patients – the extended femoral hematomas.
 Conclusion. Operative treatment in the RFA volume or endovenous laser coagulation of the stem on the level of reflux with ligature/ablation of perforant veins after conduction of anticoagulant therapy on stage of total recanalization are indicated in patients, suffering thrombosis of the big subcutaneous vein or small subcutaneous vein and deep veins of the shin. In the patients, suffering thrombosis of stem, the deep shin veins after conduction of operative treatment it is mandatory to administer anticoagulant therapy in the treatment dosage during 7 - 14 days, depending on indices of soluble complexes of the fibrin monomers and/or D-dimer.

Volume and Shape Assessment of Renal Radiofrequency Ablation Lesion

To evaluate the microscopic characteristics and quantify the volume of a radiofrequency ablation (RFA) lesion. Ten male pigs were submitted to laparoscopic RFA. An RFA needle was introduced in the lower pole of the left kidney to create a lesion expected to be a sphere of 2.0 cm diameter. The animals were followed up for 21 days. Kidneys were weighed and the volume was assessed using Scherle's method. Cavalieri's principle was used to assess the RFA volume, and sphericity was calculated to assess RFA lesion. One sample t test was used to compare RFA volume with the volume of a sphere of 2.0 cm diameter, and sphericity to hypothetical values of a sphere and an icosahedron. Fragments of RFA region were histologically evaluated. Three animals developed postoperative complications and were excluded from the analyses. There was no difference in the mean weight and volume between right and left kidneys following RFA. The mean total volume of RFA injury was 3.44 cm3. There was no difference in the RFA volume in comparison with hypothetical volumes of a sphere and an icosahedron of 2.0 cm diameter. Sphericity of the RFA injury was not similar with a sphere; however, it was similar to an icosahedron. Histology revealed areas of coagulation necrosis, fibrosis, and inflammatory mononuclear infiltration. Areas with normal tissue were also observed. The volume of injury caused by RFA was as expected and its shape was comparable with an icosahedron. Microscopic evaluation revealed areas of normal-appearing tissue.

Combined radiofrequency ablation with intrahepatic vascular occlusion using laser ablation in dogs: in vivo experimental studies

Objective To explore the feasibility and experimental conditions of laser ablation in occluding great liver vessels of dogs and whether the volume of radiofrequency ablation (RFA) could be expanded by combining with intrahepatic vascular occlusion. Methods Ten UK Beagles were divided into two groups randomly.UK Beagles were numbered as D1 to D5 in group 1 and as D6 to D10 in group 2. Laser ablation, with the fiber exposed of 1.0 cm and total power of 1 800 J, was used to block the left or middle hepatic blood vessels of D1~D5 in group 1 firstly. Laser ablation was end when color Doppler imaging showed no blood signal in the selected portal vein and hepatic artery. Contrast enhanced ultrasound (CEUS) was performed to assess the blood supply of the selected lobe of canine liver 30 min after laser ablation.Right after CEUS was performed, single point single ablation was carried out in this lobe using RFA. The same procedure of RFA was performed in the left or middle lobe of D6~D10 in group 2. The volume of radiofrequency ablation was measured using CEUS 6 days after ablation. Results Reduced or no enhancement was seen in the partial or entire liver lobe on CEUS after laser ablation. The average ablation volume was (111.7±70.4)cm3 in D1~D5 and (10.0±2.0)cm3 in D6~D10, respectively, the difference was statistically significant (P=0.032). Conclusions Great liver vessels in dogs could be partially or completely occluded by using laser ablation, causing liver lobe to part or all of ischemia or necrosis, the volume of radiofrequency ablation could be expanded by blocking the blood vessels. Key words: Ultrasonograhpy; Microbubbles; Catheter ablation; Laser therapy; Liver

Positive correlation between endoscopist radiofrequency ablation volume and response rates in Barrett's esophagus

Radiofrequency ablation (RFA) has become an accepted form of endoscopic treatment for Barrett's esophagus (BE), yet reported response rates are variable. There are no accepted quality measures for performing RFA, and provider-level characteristics may influence RFA outcomes. To determine whether endoscopist RFA volume is associated with rates of complete remission of intestinal metaplasia (CRIM) after RFA in patients with BE. Retrospective analysis of longitudinal data. Three tertiary-care medical centers. Patients with BE treated with RFA. For each endoscopist, we recorded RFA volume, defined as the number of unique patients treated as well as corresponding CRIM rates. We calculated a Spearman correlation coefficient relating these 2 measures. We identified 417 patients with BE treated with RFA who had at least 1 post-RFA endoscopy with biopsies. A total of 73% of the cases had pretreatment histology of high-grade dysplasia or adenocarcinoma. The procedures were performed by 7 endoscopists, who had a median RFA volume of 62 patients (range 20-188). The overall CRIM rate was 75.3% (provider range 62%-88%). The correlation between endoscopist RFA volume and CRIM rate was strong and significant (rho= 0.85; P= .014). In multivariable analysis, higher RFA volume was significantly associated with CRIM (P for trend .04). Referral setting may limit generalizability. Limited number of endoscopists analyzed. Endoscopist RFA volume correlates with rates of successful BE eradication. Further studies are required to confirm these findings and to determine whether RFA volume is a valid predictor of treatment outcomes in BE.

Percutaneous Radiofrequency Ablation of Hepatocellular Carcinoma against the Diaphragm: Is Artificial Ascites Necessary?

Purpose: To evaluate the utility of artificial ascites induction for radiofrequency ablation (RFA) of peridiaphragmatic hepatocellular carcinoma (HCC) through retrospective cohort analysis comparing characteristics and complications of peridiaphragmatic HCC without the use of artificial ascites to non-peridiaphragmatic HCC. Materials and Methods: IRB approval was obtained. From September 2003 to December 2008, 150 consecutive patients with hepatic tumors received percutaneous RFA. 110 patients had presumed HCC, and of those 21 had lesions abutting the diaphragm. Of the remaining 89 patients with non-peridiaphragmatic HCC lesions, 21 were randomly selected for the comparison group. RFA volume, major and minor complication rates, pain, technical success, and recurrence rates were compared between the two groups. Results: There was no statistical difference in RFA volume (P = 0.962), overall major complication rate (P = 0.343) and minor complication rate (P = 0.118) between the two groups. However, the peridiaphragmatic group that underwent RFA with a clustered-needle demonstrated a statistically significant higher proportion of major complications compared to the non-peridiaphragmatic clustered-needle group (P = 0.033). There was no statistical difference in pain severity (P = 0.8802) or pain location (P = 0.15). There was no statistical difference in technical success rates (P = 1), local tumor progression rates (P = 1), or time to local tumor recurrence (P = 0.67). Conclusion: Artificial ascites induction for RFA of HCC lesions adjacent to the diaphragm may not be necessary, although clustered electrode technique should be avoided in this location as they present with a higher complication rate.

Sa1462 Correlation Between Endoscopist Radiofrequency Ablation Volume and Response Rate in the Treatment of Barrett's Esophagus

Although there has been intense interest in linking outcomes of common endoscopic procedures such as screening colonoscopy to endoscopist-level factors such as procedural volume, no similar data exists for radiofrequency ablation (RFA) of Barrett's esophagus (BE). We sought to determine whether endoscopist RFA volume correlated with the rate of complete remission of intestinal metaplasia (CRIM) after RFA treatment.

Short-Term Outcomes of Ablation Therapy for Hepatic Tumors: Evidence from the 2006–2009 Nationwide Inpatient Sample

Radiofrequency ablation (RFA) for the treatment of hepatic tumors has been increasingly used across the United States. Whether treatment-related morbidity has remained low with broader adoption is unclear. We conducted this study to describe in-hospital morbidity associated with RFA for hepatic tumors and to identify predictors of adverse events in a nationally representative database. Using the 2006-2009 Nationwide Inpatient Sample, we evaluated all patients aged ≥40years who underwent an elective RFA for primary or metastatic liver tumors (N=1298). Outcomes included in-hospital procedure-specific and postoperative complications. Multivariable logistic regression analyses were performed to identify patient and facility predictors of complications. Most patients underwent a percutaneous (39.9%) or laparoscopic (22.0%) procedure for metastatic liver tumors (57.5%). Procedure-specific complications were frequent (18.2%), with transfusion requirements (10.7%), intraoperative bleeding (4.3%), and hepatic failure (2.8%) being the most common. Arrhythmias [adjusted odds ratio (AOR)=1.93 (1.23-3.04)], coagulopathy [AOR=4.65 (2.95-7.34)], and an open surgical approach [AOR=2.77 (1.75-4.36)] were associated with an increased likelihood of procedure-specific complications, whereas hospital RFA volume ≥16/year was associated with a reduced likelihood [AOR=0.59 (0.38-0.91)]. Postoperative complications were also common (12.0%), with arrhythmias, heart failure, coagulopathy, and open surgical approach acting as significant predictors. In-hospital morbidity is common after RFA for hepatic tumors. While several patient factors are associated with more frequent procedure-specific complications, treatment at hospitals with an annual volume ≥16 cases/year was associated with a 41% reduction in the odds of procedure-specific complications.

Temperature-dependent Electrode Repositioning for Multiple Overlapping Radiofrequency Ablation in Ex Vivo Porcine Livers

Overlapping ablations can be used to increase radiofrequency ablation volume. Our goal was to determine, in a porcine model, the relationship of ablation size and temperature for single ablation, and to compare the extent of necrosis resulting from temperature-dependent electrode positioning versus fixed-distance dual ablation. The experiments were performed in two parts (single and dual ablations). During single ablation in ex vivo porcine livers, maximum necrotic diameter was compared with the diameters at the level at which temperatures reached 60°C, 55°C, and 50°C. Dual ablations were performed using 60°C (group 60C), 55°C (group 55C), and 50°C (group 50C), and distances of 3 cm (group 3cm) and 4.1cm (group 4.1cm) as the starting point (RFA2-start) for the second ablation. The maximum necrotic diameter (3.3 ± 0.6 cm) and the necrotic diameters reached at 60°C (2.8 ± 0.8 cm) and 55°C (2.2 ± 0.7 cm) were significantly greater than that at 50°C (0.9 ± 0.5cm; P < .05). In dual ablations, there was no difference between RFA2-start and the maximum diameter of the preceding and subsequent ablations in all temperature-dependent dual ablations (groups 60C, 55C, and 50C) and in group 3cm. (P > .05) However, there was a significant difference between RFA2-start and maximum diameter of the preceding and subsequent ablations in Group 4.1cm (P = .038), resulting in dumbbell-shaped necrosis. The necrotic diameter proportionally decreases with the temperature in single ablation. Withdrawing the electrode up to 50° or by 3 cm before reablating results in fusion of the two ablation zones versus withdrawal of 4.1 cm, which results in incomplete necrosis in between two ablation zones.

Expansion of radiofrequency ablation volume by saturated NaCL saline injection in the area of vaporization

Vaporization around the radiofrequency (RF) electrode after RF application (RFA) limits the RF ablation area. To determine whether saturated saline injected into the area of vaporization after initial RFA extends ablation area after further RFA. RFA was performed in 18 ex vivo porcine livers and four in vivo rabbit erector spinae muscles. An RF electrode was used to ablate an area with 40W of parallel current for 15 min. The ablation margin was determined using a thermocouple, and the radius of the ablated area was measured. After RF electrode removal, saturated saline was infused through a percutaneous ethanol injection needle into the site of the original RFA in 11 liver samples and two erector spinae muscles. Three minutes later, RFA was resumed for 15 min. The remaining seven control liver samples and two spinae muscles received RFA without saline injection. The radius of the final ablated area was then measured. In the ex vivo study, injection of saturated saline significantly decreased tissue impedance (87.7+/-9.4 to 51.1+/-9.7 Omega, P<0.0001), and increased the mean radius of the ablated area (15.9+/-3.0 to 25.0+/-3.6 mm, P<0.0001). These significant changes were not observed without injection of saturated saline. Similar trends were found in the in vivo study. Injection of saturated saline into the area of vaporization around the RF electrode, followed by additional RFA, caused concentric expansion of the final ablation area, facilitating more efficient tumor ablation.

Effectiveness of Hepatic Arterial Embolization on Radiofrequency Ablation Volume in a Swine Model: Relationship to Portal Venous Flow and Liver Parenchymal Pressure

To evaluate the effectiveness of transcatheter arterial embolization (TAE) on radiofrequency (RF) ablation volume and compare portal vein (PV) flow and liver parenchymal pressure before and after treatment. Eight healthy female swine were divided into four groups to be treated with RF ablation alone (RF-only group), RF ablation after TAE with gelatin sponge particles (GSPs; RF/TAE group), RF ablation after TAE with Lipiodol plus GSPs (RF/TAE/Lipiodol group), and PV embolization (PVE) with GSPs after TAE with Lipiodol plus GSPs (RF/TAE/Lipiodol/PVE group). Five ablations were created in each swine, with 10 ablations per group. A 2-cm expandable LeVeen needle electrode was used for RF ablation. The greatest ablation volume (18,410.1 mm(3) +/- 3,986.4) was observed in the RF/TAE/Lipiodol/PVE group. Of the RF-only, RF/TAE, and RF/TAE/Lipiodol groups, the RF/TAE/Lipiodol group (14,835.5 mm(3) +/- 2,743.2) had a significantly larger ablation volume than the RF-only (8,002.6 mm(3) +/- 2,788.3) and RF/TAE groups (10,398.5 mm(3) +/- 2965.8; P < .05/3). PV pressures increased significantly after TAE (P < .01) compared with the pressure before TAE in the RF/TAE/Lipiodol and RF/TAE/Lipiodol/PVE groups, but not in the RF/TAE group. A marked increase in liver parenchymal pressure was seen during RF ablation; however, there were no significant differences among groups. Accumulation of Lipiodol was noted in the sinusoids in the RF/TAE/Lipiodol and RF/TAE/Lipiodol/PVE groups. TAE with blockade of PV flow before RF ablation was associated with greater ablation volumes. Liver parenchymal pressure showed no correlation with increased ablation volume.

Effect of Multisite Radiofrequency Ablation on Porcine Renal Function

The acute and long-term effects of radiofrequency ablation (RFA) on kidney function have not been well studied. The functional change when RFA is used in combination with renal ischemia is likewise unknown. Our goal was to determine the change in renal function caused by various volumes of RFA on a porcine kidney model and the effect cold ischemia had on the results. Twenty-two female pigs with solitary kidneys underwent various volumes of RFA both with and without cold ischemia. Animals were divided into control, 10%, 15%, and 20% ablation of the total kidney volume. Measurements of creatinine were obtained for 2 weeks. In the nonischemic group, the mean acute (day 1-3) creatinine changes in control, 10%, 15%, and 20% ablations were 0.6, 2.4, 1.7, and 2.6 mg/dL, respectively. In the cold-ischemia group, the mean acute creatinine changes were 0.85, 2.33, 3.3, and 3.75 mg/dL, respectively. Regression line analysis demonstrated a positive linear relationship in both groups. Fourteen-day mean creatinine changes for the nonischemic group were similar to those in the control animals and did not show a correlation with ablation volume. The mean creatinine changes at 14 days in the cold-ischemia group showed a positive linear correlation with ablation volume. The volume of RFA correlates with an acute change in renal function in the porcine model for both nonischemic and cold-ischemia groups. This study may help predict the extent of acute renal dysfunction in patients undergoing RFA for large or multiple renal masses. These results also suggest renal function may recover after nonischemic RFA.

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 3.350.56cm and 19.96.53 , respectively, for the expandable needle and 3.580.78 cm and 23.195.27 , respectively, for the cooled-tip needle. In the ex vivo model, the mean diameter and volume of RFA induced lesions were 3.410.59 cm and 26.598.02 , respectively, for the expandable needle, and 4.040.65 cm and 33.826.16 , respectively, for the cooled-tip needle (p