Radiofrequency Ablation Electrode Research Articles

Partial resection of the splenic cyst using radiofrequency ablation system

Introduction. This paper presents a case of a patient with a benign splenic cyst, which was removed by way of partial resection of the spleen. Case outline. The patient?s benign cyst in the lower pole of the spleen was excised using single CooltipTM radiofrequency ablation electrode (Cool-tip RF Ablation System, CovidienTM, Dublin, Ireland). More than half of the spleen was excised without setting stitches to the splenic parenchyma and without any other hemostyptics. This way, the function of the spleen was preserved, which was proven with scintigraphy and computed tomography two years after the intervention. Conclusion. Radiofrequency ablation system with internally cooled needles can be used successfully and without any consequences to the organ, especially in case of large benign splenic cysts, when it is necessary to preserve the function of the spleen.

A new approach to feedback control of radiofrequency ablation systems for large coagulation zones

Aim: The aim of this study was to investigate the feasibility of achieving relatively large coagulation zones (i.e. ≥3 cm in diameter) with radiofrequency ablation (RFA) by using a broad control system.Materials and methods: A broad control system consists of information such as (i) the area of the tumour tissue for feedback control, (ii) the set-point temperature and (iii) the control law. The proposed approach has advanced knowledge in (i) and (ii) in particular. RFA is known to be limited by tissue dehydration that occurs around the electrode, which results in impedance such that no further energy can be delivered to the tissues. We proposed the notion of “energy gate”, an area on the electrode, which is not covered by the dehydrated tissue and through which energy can still be delivered to the surrounding tissues. Given a specific size of energy gate, both (i) the area of the tissue in which the temperature is monitored and (ii) the set-point temperature were determined. A reliable finite element model or simulator for a commercially available electrode was used and the tissue surrounding the RFA electrode was divided into three areas for a comprehensive study of the issues (i) and (ii). Porcine liver tissue (30 specimens in total) and a custom-made RFA device with a RF power generator (100 W and 460 ± 30 kHz) and a Covidien cool-tip electrode (17 gauge and 30 mm exposure) were used to validate the findings regarding the area of the tissue for feedback control and the set-point temperature.Results: The size of coagulation zone achieved was maximised when the area of tissue surrounding the middle part of the active tip (i.e. Point 7) was used for feedback control and when the set-point temperature was set to 90 ^ C (this temperature is determined based on the energy gate through a trial-and-error procedure). At both 80 and 90 ^ C, the coagulation zones generated using Area II were significantly larger than that generated using Area I (p = 0.0028 and 0.0003, respectively) and Area III (P = 0.0010 and < 0.0001, respectively). A similar finding regarding the control area and set-point temperature was confirmed by the in-vitro experiment. When compared with Point a (p < 0.0001) and Point c (p < 0.0001), the largest coagulation zone (1066.7 ± 36.1 mm2) was achieved by controlling the temperature of the tissue area surrounding the middle part of the active tip (i.e. Point b) at 90 ^ C.Conclusion: The judicious selection of the control area within the biological tissue for temperature monitoring and the set-point temperature for feedback control is critical in increasing the size of the coagulation zone in the treatment of RFA.

A Thermographic Comparison of Irreversible Electroporation and Radiofrequency Ablation

Radiofrequency ablation and irreversible electroporation are both interventional procedures used in treating cancer diseases generally and may be used in treatment of liver cancer. The two differ in terms of their action and thermal effects. The present study examined thermal effects of radiofrequency ablation and modified irreversible electroporation ex vivo in porcine liver. Standard radiofrequency ablation was used during the experiments, as was a unique, experimental high-voltage generator of the research team's own construction coupled with a newly designed balloon electrode catheter for irreversible electroporation. The tested balloon catheter was newly designed for application in the biliary tract. The temperature of porcine liver tissue was monitored without contact by infrared camera. The results show significantly different temperature of tissue around electrodes for radiofrequency ablation and irreversible electroporation. The data obtained from radiofrequency ablation with maximum tested output power of 10 watts show a symmetrical area of tissue near active electrodes with temperature increased by more than 30 °C. Irreversible electroporation methods showed temperature increasing approximately by 5 °C. To summarize, the thermal research showed that the difference between standard RFA and innovated IRE with the balloon catheter lies not just in the differing mechanism of action, as is well known, but also in its thermal effects. There was documented that tissue temperature was much higher for RFA than for IRE, particularly for the maximum tested output parameters. The applicability of the newly designed balloon catheters was confirmed.

Temperature distribution during radiofrequency ablation of spinal metastases in a human cadaver model: Comparison of three electrodes.

Radiofrequency ablation (RFA) temperatures reaching 45°C in adjacent tissues are cytotoxic to the spinal cord, nerves and surrounding tissues. This study compares different RFA electrodes with regard to the temperature distribution during ablation of spinal metastases. In vitro experimental study in isolated lumbar vertebrae of a human cadaveric spine. The temperature distribution of RFA electrodes was measured during ablation in human cadaveric lumbar vertebrae containing a simulated vertebral body lesion. The analysis compared a novel bipolar RFA electrode with two conventional monopolar RFA electrodes. A vertebral metastasis model was prepared in eight lumbar vertebrae for each electrode. Differences between the electrodes were evaluated with a one-way ANOVA. The lowest temperature at the thermocouples adjacent to the simulated lesion was achieved when using the bipolar RFA electrode (46.4 ± 3.3°C), but temperature difference to the monopolar RFA electrodes was not significant. In the neural foramen and epidural space of lumbar vertebrae the maximal temperature measured when using the bipolar RFA electrode was 37.0 ± 0°C and 37.3 ± 0.7°C, which was significantly lower than during ablation via either of the monopolar RFA electrodes (p ≤ 0.001). Temperatures in areas of adjacent tissue during RFA using a specific for spinal ablation designed electrode with integrated thermocouples were significantly lower compared to other electrodes, potentially reducing temperature related risks during ablation.

Endoscopic ultrasound-guided ablation of branch-duct intraductal papillary mucinous neoplasms: Feasibility and safety tests using porcine gallbladders.

Radiofrequency ablation (RFA) and ethanol ablation are accepted methods of tissue destruction for treating cystic tumors. The aim of the present study was to evaluate the feasibility, efficacy, and safety of endoscopic ultrasound (EUS)-guided ablation using normal porcine gallbladders as a substitute model for branch-duct intraductal papillary mucinous neoplasms (BD-IPMN). Six adult mini pigs were included in this prospective study. EUS-guided RFA with or without ethanol ablation of the gallbladder was carried out using a prototype 18-gauge endoscopic RFA electrode, and RFA and ethanol ablation were done in a single session. Outcomes were assessed in terms of macroscopic and microscopic evaluations of the treated gallbladders. The prototype RFA electrode was used for ablation of the mucosa, aspiration of the internal contents of the gallbladder, and ethanol injection. RFA plus ethanol lavage resulted in a greater mean percentage of denuded gallbladder mucosa (97.5%) than RFA alone (55.8%). Effects of ablation extending to the cystic duct and partially denuded cystic duct mucosae were detected in five of the six pigs. There were no major procedure-related adverse events. EUS-guided ablation of the gallbladder mucosa was feasible and effective in the porcine model. Additional studies will be required to fully assess the risk of procedure-related damage to the main pancreatic duct before using this technique in a clinical setting.

Angled Cool-Tip Electrode for Radiofrequency Ablation of Small Superficial Subcapsular Tumors in the Liver: A Feasibility Study

ObjectiveTo evaluate the feasibility of angled cool-tip electrode for radiofrequency ablation of small superficial subcapsular liver tumors abutting abdominal wall, in order to traverse normal liver parenchyma, and thereby, obtain favorable configuration of ablation margin.Materials and MethodsIn this study, we retrospectively analyzed 15 small superficial subcapsular liver tumors abutting abdominal wall in 15 patients, treated with radiofrequency ablation from March 2013 to June 2015 using a cool-tip electrode manually modified to create 25–35° angle at the junction between exposed and insulated segments. The tumors were hepatocellular carcinoma (n = 13) and metastases (n = 2: cholangiocellular carcinoma and rectosigmoid cancer), with maximum diameter of 10–26 mm (mean, 15.68 ± 5.29 mm). Under ultrasonographic guidance, the electrode tip was advanced to the depth of the tumors' epicenter about 1 cm from the margin. The tip was re-directed to penetrate the tumor for radiofrequency ablation. Minimal ablation margin was measured at immediate post-treatment CT. Radiological images and medical records were evaluated for success rate, length of minimal ablation margin and complications.ResultsTechnical success rate of obtaining complete necrosis of the tumors was 100%, with no procedure-related complication. Minimal ablation margin ranged from 3–12 mm (mean, 7.07 ± 2.23 mm). CT/MRI follow-up at 21–1022 days (mean, 519.47 ± 304.51 days) revealed no local recurrence, but distant recurrence in 9 patients.ConclusionUsing an angled cool-tip electrode for radiofrequency ablation of small superficial subcapsular tumors abutting abdominal wall may be a feasible technique for obtaining adequate ablation margin and lower complication rate.

Development of a Swine Benign Biliary Stricture Model Using Endoscopic Biliary Radiofrequency Ablation.

The large animal model with benign biliary stricture (BBS) is essential to undergo experiment on developing new devices and endoscopic treatment. This study conducted to establish a clinically relevant porcine BBS model by means of endobiliary radiofrequency ablation (RFA). Endoscopic retrograde cholangiography (ERC) was performed on 12 swine. The animals were allocated to three groups (60, 80, and 100 W) according to the electrical power level of RFA electrode. Endobiliary RFA was applied to the common bile duct for 60 seconds using an RFA catheter that was endoscopically inserted. ERC was repeated two and four weeks, respectively, after the RFA to identify BBS. After the strictures were identified, histologic evaluations were performed. On the follow-up ERC two weeks after the procedure, a segmental bile duct stricture was observed in all animals. On microscopic examination, severe periductal fibrosis and luminal obliteration with transmural inflammation were demonstrated. Bile duct perforations occurred in two pigs (100 W, n = 1; 80 W, n = 1) but there were no major complications in the 60 W group. The application of endobiliary RFA with 60 W electrical power resulted in a safe and reproducible swine model of BBS.

The Effectiveness of Multiple Electrode Radiofrequency Ablation in Patients with Hepatocellular Carcinoma with Lesions More than 3 cm in Size and Barcelona Clinic Liver Cancer Stage A to B2

Outcomes of hepatocellular carcinoma (HCC) lesions >3.0 cm in size including Barcelona Clinic Liver Cancer (BCLC) stage B after radiofrequency ablation (RFA) with a single electrode remain unsatisfactory. This study aimed to investigate the outcomes of RFA with multiple electrodes (ME-RFA) for HCC tumors 3.1-7.0 cm in size and BCLC stage B. This retrospective study included 70 consecutive patients with 58 medium- (3.1-5.0 cm) and 17 large- (5.1-7.0 cm) sized HCCs after ME-RFA using a controller. Outcomes in terms of complete response, primary technique effectiveness, local tumor progression, and overall survival were investigated. After 1-4 applications of ME-RFA, the rates of complete response and PTE in medium-sized tumors were 79.3% and 91.4%, respectively, and in large tumors were 76.5% and 94.1%, respectively. Overall, the major complication rate was 5.7%. After a median 21-month follow-up period, both two- and three-year estimated overall survival rates were above 80%. There were no significant differences in overall survival and local tumor progression rates between medium- and large-size tumors and among BCLC stages A, B1 and B2. A complete response to ME-RFA was the only significant factor associated with improved survival (p=0.008). In conclusion, ME-RFA can effectively treat 3.1-7.0-cm sized HCCs with a comparable outcome between medium- and large-size tumors and among BCLA stages A to B2.

Initial experience of EUS-guided radiofrequency ablation of unresectable pancreatic cancer

Radiofrequency ablation (RFA) has been used as a valuable treatment modality for various unresectable malignancies. EUS-guided radiofrequency ablation (EUS-RFA) of the porcine pancreas was reported to be feasible and safe in our previous study, suggesting that EUS-RFA may be applicable as an adjunct and effective alternative treatment method for unresectable pancreatic cancer. This study aimed to assess the technical feasibility and safety of EUS-RFA for unresectable pancreatic cancer. An 18-gauge endoscopic RFA electrode and a radiofrequency generator were used for the procedure. The length of the exposed tip of the RFA electrode was 10 mm. After insertion of the RFA electrode into the mass, the radiofrequency generator was activated to deliver 20 to 50 W ablation power for 10 seconds. Depending on tumor size, the procedure was repeated to sufficiently cover the tumor. EUS-RFA was performed successfully in all 6 patients (median age 62 years, range 43-73 years). Pancreatic cancer was located in the head (n = 4) or body (n = 2) of the pancreas. The median diameter of masses was 3.8 cm (range 3cm-9cm). Four patients had stage 3 disease, and 2 patients had stage 4 disease. After the procedure, 2 patients experienced mild abdominal pain, but there were no other adverse events such as pancreatitis or bleeding. EUS-RFA could be a technically feasible and safe option for patients with unresectable pancreatic cancer.

Modelling of a bipolar stent-based electrode for thermal radio frequency ablation of tumours located in hollow organs

Purpose – In this paper a numerical simulation analysis of a modified stent-based electrode is introduced to be used as a bipolar electrode for radio frequency ablation of tumours located in hollow organs. The purpose of this paper is to study the possibility of achieving a more regular volume of induced lesion with the presented electrode without imperilling the ductal organ where the tumour is located. Design/methodology/approach – Three types of bipolar electrode configurations were considered, formed by two, three and five tubular segments. Numerical simulations were performed considering a tumour located in the bile duct, where two important blood vessels – the portal vein and the hepatic artery – have a significant impact due to the convective heat transfer caused by the blood flow (heat sink effect) which significantly affects the shape of lesion that is intended to induce in order to destroy the tumour. Findings – The results obtained show that the five-segment electrode arrangement allows a regular volume for the induced lesion, independently of the different values of applied voltage considered. Originality/value – The presented work introduces a numerical simulation analysis on a modified based-stent electrode previously studied. In this case, the electrode is configured so it can be used as a bipolar electrode, i.e., active and ground electrode are placed in the same device. Besides the results evinced by the obtained results, this kind of electrode avoids eventual skin burns that might occur due to the need of the return electrodes when monopolar electrodes are used.

In vitro artefact assessment of a new MR-compatible microwave antenna and a standard MR-compatible radiofrequency ablation electrode for tumour ablation.

To evaluate and compare artefact configuration and diameters in a magnetic resonance (MR)-compatible prototype microwave (MW) applicator and a standard MR-compatible radiofrequency (RF) applicator for MR-guided tumour ablation. Both applicators were tested in a phantom study at 1.5T with three sequences: T1-weighted three-dimensional volume interpolated breath-hold examination (VIBE), T1-weighted fast low angle shot (FLASH), T2-weighted turbo spin echo (TSE). Applicator orientation to main magnetic field (B0) and slice orientation were varied. Needle tip location error (TLE) was assessed, and artefact diameters were calculated. Influence of imaging parameters on artefacts was assessed with analysis of variance (ANOVA) and post hoc testing. MW applicator: the shaft artefact diameter measured 2.3 +/- 0.8 mm. Tip artefact diameter and length measured 2.2 ± 0.8 mm and 2.4 ± 1.3 mm, respectively. A prominent oval artefact (diameter: 16.5 +/- 1.8 mm, length: 19.1 +/- 2.5 mm) appeared close to the tip. TLE: - .3 +/- 0.6 mm. RF applicator: shaft and tip diameter measured 8.9 +/- 4.7 mm and 9.0 +/- .0 mm, respectively. TLE: -0.1 +/- 0.8 mm. Minimal artefacts were measured with RF applicator orientation parallel to B0 (P < 0.0001), whereas no such influence was found for MW applicator. For both applicators, significantly large artefacts were measured with T1 FLASH (P = 0.03). The MW applicator's artefact is satisfactory and seems useable for MR-guided ablation procedures. MW applicator's artefact appearance is independent of angulation to main magnetic field. MW applicator's prominent distal artefact may increase visibility under MR-guidance. RF and MW applicator's artefacts are precise concerning tip depiction. Largest artefact diameters are measured with T1-weighted fast low angle shot sequence.

Helical coil electrode radiofrequency ablation designed for application in osteolytic vertebral tumors—initial evaluation in a porcine model

Background contextRadiofrequency ablation (RFA) is emerging as a complementary treatment for vertebral metastases. Traditional RFA induces frictional heating leading to local tissue necrosis but often yields small, incomplete, and inhomogeneous zones of ablation in bone. We have developed a new bone-specific RFA electrode that uses a nontraditional frequency (27.12 MHz) and geometry (helical), exploiting a magnetic field and an electric field to generate larger and more comprehensive treatment zones. PurposeThe purpose of the study was to evaluate the feasibility and safety of the Bone Coil RFA electrode in the spine. Study designThis is a preclinical in vivo study based on basic science. MethodsUnder institutional approval, six healthy Yorkshire pigs received a sham and an RF treatment in two adjacent cervical vertebrae. To deploy the Bone Coil RFA device in dense porcine vertebrae, a surgical approach was required; an irrigated coring drill bit created a cylindrical path in the vertebral bodies through which the RFA electrodes were placed. The electronic circuit was completed by four grounding pads. Treatment was delivered for 10 minutes at 20 W (n=1), 25 W (n=1), and 30 W (n=4). To monitor the thermal rise and for safety, fiber-optic probes recorded temperatures in the center of each coil and near the spinal foramen. After the procedure, animals were monitored for 2 weeks. Magnetic resonance imaging (MRI) was completed immediately after treatment and at 14 days. Magnetic resonance image segmentation and histology were used to evaluate the ablation volume. ResultsComprehensive treatment of the porcine vertebrae was demonstrated by temperature monitoring, MRI, and histology. Large zones of RF ablation were obtained (RF: 3.72±0.73 cm3 vs. sham: 1.98±0.16 cm3, p<.05), confined within the vertebral body. Internal temperatures were elevated with RF (66.1°C–102.9°C), without temperature rise outside of the vertebrae (38.2°C±1.5°C). Mobility, neurological responses, and behavior were normal, consistent with preprocedural examination. Magnetic resonance imaging best visualized ablation at Day 14. Histology revealed comprehensive homogeneous coagulative necrosis with little peripheral sign of repair. ConclusionsThe Bone Coil RFA device created large intravertebral ablation volumes with no neurologic sequelae. Radiofrequency thermal ablation (clearly distinguished from the much smaller effects arising from core drilling) corresponded to the homogeneous necrosis visible on histology.

Radiofrequency ablation of small breast tumours: Evaluation of a novel bipolar cool-tip application

BackgroundAlthough radiofrequency ablation (RFA) is promising for the local treatment of breast cancer, burns are a frequent complication. The safety and efficacy of a new technique with a bipolar RFA electrode was evaluated. MethodsDosimetry was assessed ex vivo in bovine mammary tissue, applying power settings of 5–15 W with 10–20 min exposure and 3.0–12.0 kJ to a 20-mm active length bipolar internally cooled needle-electrode. Subsequently, in 15 women with invasive breast carcinoma ≤2.0 cm diameter ultrasound-guided RFA was performed followed by immediate resection. ResultsAn ablation zone of 2.5 cm was reached in the ex vivo experiments at 15 W at 9.0 kJ administered energy. Histopathology revealed complete cell death in 10 of 13 patients (77%); in 3 patients partial ablation was due to inaccurate probe positioning. In 1 patient a pneumothorax was caused by the probe placement, treated conservatively. No burns occurred. ConclusionsUltrasound-guided RFA with a bipolar needle-electrode appears to be a safe local treatment technique for invasive breast cancer up to 2 cm. Ways to improve placement of the probe and direct monitoring of the ablation-effect should be the aim of further research.

Radiofrequency ablation guided by contrast-enhanced ultrasound for hepatic malignancies: Preliminary results

To evaluate whether contrast-enhanced ultrasound (CEUS)-guided radiofrequency ablation (RFA) can be performed effectively in small hepatic malignancies that are invisible or poorly visualized at traditional grey-scale ultrasonography (US). The institutional ethics committee approved the study, and all patients provided written informed consent before their enrolment. The study focused on 55 patients (43 men, 12 women, age 57.4 ± 10.9 years) with 60 hepatic lesions from May 2010 to March 2011. All lesions were treated with multipolar radiofrequency ablation (RFA). During the RFA procedure, with the injection of ultrasound contrast agent (sulphur hexafluoride; SonoVue, Bracco Imaging Spa, Milan, Italy), RFA was conducted under CEUS guidance when the optimal depiction of a lesion was obtained. Artificial pleural effusions were used in those cases obstructed by the lungs. Twenty-four hours after RFA, contrast-enhanced MRI was used as the reference standard to evaluate the primary effectiveness rate and complete tumour necrosis. The follow-up time was 12-24 months (median 15 months). Among 60 hepatic malignancies, CEUS detected 57 lesions (95%), which was higher than that at US (26.6%). Artificial pleural effusions were performed in three cases, resulting in the detection of three additional lesions. The insertion of RFA electrodes was monitored by CEUS in all lesions. Immediately after RFA, complete tumour necrosis were achieved in all 60 lesions as apparent at MRI, for a primary effectiveness rate of 100%. CEUS-guided RFA is a promising technique for targeting and improving the efficiency of treatment of hepatic malignancies.

The safety and treatment response of combination therapy of radioimmunotherapy and radiofrequency ablation for solid tumor: a study in vivo.

ObjectionTo investigate the safety and treatment response of radioimmunotherapy (RIT) in combination with radiofrequency ablation (RFA) for the treatment of VX2 tumor on rabbit.Materials and MethodsA total of 36 rabbits bearing VX2 tumor on the thigh were randomly assigned into 3 groups (group I: 1–2 cm; group II: 2–3 cm; group III: 3–4 cm) and 4 subgroups (A: as control, just puncture the tumor using the RFA electrode without power output; B: RFA alone; C: 131I-chTNT intratumoral injection alone; D: RFA+131I-chTNT intratumoral injection 3 days later). The variation of blood assay, weight and survival among different groups and subgroups were used to assess the treatment safety. Ultrasound (US) was used to monitor and assess the tumor response after treatment.ResultsAccording to the results of the weight and the blood assay among different groups, subgroups, and at two time points (one day before and the 16th day after treatment), no damages to the liver, kidney function and myelosuppression resulting from the treatment were found. No significant differences in survivals among the four subgroups (p = 0.087) were found. In addition, 131I-chTNT did not show significant inhibition effect on VX2 tumor progression according to US measurements.Conclusion 131I-chTNT intratumoral injection alone or in combination with RFA is relatively safe for rabbit without significant toxicity and shows no significant effect on the survival. The treatment response is not as satisfactory as anticipated.

Combined radiofrequency ablation and ethanol injection with a multipronged needle for the treatment of medium and large hepatocellular carcinoma.

To evaluate the efficacy and safety of combined radiofrequency ablation (RFA) and ethanol injection with a multipronged needle in the treatment of medium (3.1-5.0 cm) and large (5.1-7.0 cm) hepatocellular carcinoma (HCC). A total of 65 patients with 67 HCC nodules were enrolled in this prospective study. All of them received the treatment of combined RFA and multipronged ethanol injection percutaneously. The average volume of injected ethanol was 14.4 ± 4.1 ml (range, 9-30 ml). The average number of RFA electrode insertions was 1.7 ± 0.8 (range, 1-4). The rate of initial local complete response (CR) was 94.0 % (63/67). After additional treatment, technical success was achieved in all HCC nodules. There were no treatment-related deaths, and major complications were observed in 3 (4.6%) patients. After a mean follow-up of 20.0 ± 7.6 months, local tumour progression was observed in 10 (10/67, 14.9%) tumours, whereas distant recurrence developed in 32 (32/65, 49.2%) patients. The 1-year and 2-year survival rates were 93.1% and 88.1%, respectively. The combination of RFA and multipronged ethanol injection in the treatment of medium and large HCC is safe and effective with a high rate of local tumour control. • Combined radiofrequency ablation and multipronged ethanol injection is a new therapeutic strategy • Treatment is safe and effective for medium and large hepatocellular carcinoma (HCC) • A multipronged needle allows for a homogeneous ethanol distribution.

Percutaneous radiofrequency ablation of renal tumours: 29-month mean follow-up results of 118 patients

Background. Percutaneous radiofrequency ablation (RFA) is a minimally invasive method of treatment based on thermal effects. This retrospective study aimed to clarify percutaneous RFA of kidney tumors – performance, extremeness and 5-year survival in patients with small renal tumors in a single center. Materials and methods. Between September 2003 and December 2012, a total of 118 patients underwent percutaneous RFA of renal tumors. During more than 9 years period 144 RFA procedures were performed. Tumors were verified by biopsy. We used 3 RFA techniques: RFA under ultrasound control only (US), ultrasound guided RFA with CT navigation (US/CT) and ultrasound guided RFA with CT navigation, fiducial markers placed around the kidney tumor before the treatment (US/CT/FM). RFA electrodes were one and three. Patients were followed up regularly by CT with contrast enhancement. Results. The mean patient age was 68.72 years (range 28 to 86). The mean tumor size was 2.8 cm (range 1 to 5.4). The mean follow-up time was 29 months (1–111 months). Radical dependence on technical procedures: only US 39 (66.1%), US/CT 18 (94.7%), US/CT/FM 37 (92.5%), p = 0.001. Radical differences between using one and three electrodes: 39 (66.1%) and 55 (93.2%), p

Thermal influence of radiofrequency ablation for bone: an experimental study in normal rabbit bone

To evaluate the heat effects of radiofrequency ablation (RFA) on normal bone by mechanical testing, MRI, and histology. The institutional animal care and use committee approved the animal study. Thirty-two adult Japanese white rabbits were included in our study. Bone biopsy needles were inserted from the distal end of the right (RFA side) and the left (control side) femurs using a fluoroscopic guide. A 17-gauge internally cooled RFA electrode with a 2-cm active tip was inserted through the needle to the right femur, and RFA was performed for 12 min using a 200-W generator. Animals were divided into four groups and 8 animals from each group were euthanized on day 1, day 7, day 30, and day 60 after RFA. MRI was performed prior to euthanasia. Three-point bending test was performed to measure flexural strength. Student's t test was used to evaluate for significant differences between RFA and control side for each group. Femurs underwent histological examination by hematoxylin and eosin staining after the bending test. MRI showed a high-intensity rim around the bone on T2WI. Three-point bending test showed no statistically significant differences (P < 0.05) between the RFA and the control side in any of the groups. Histologically, osteocytes of cortical bone showed cell death, but the lamellar structure was preserved in all groups and bone remodeling was observed. Heat by RFA did not change normal bone strength within 2 months, despite the heat effects in the cortical bone and cell death.

Considering angle selection when using ultrasound electrode displacement elastography to evaluate radiofrequency ablation of tissues.

Percutaneous radiofrequency ablation (RFA) is a minimally invasive treatment to thermally destroy tumors. Ultrasound-based electrode-displacement elastography is an emerging technique for evaluating the region of RFA-induced lesions. The angle between the imaging probe and the RFA electrode can influence electrode-displacement elastography when visualizing the ablation zone. We explored the angle effect on electrode-displacement elastography to measure the ablation zone. Phantoms embedded with meatballs were fabricated and then ablated using an RFA system to simulate RFA-induced lesions. For each phantom, a commercial ultrasound scanner with a 7.5 MHz linear probe was used to acquire raw image data at different angles, ranging from 30° to 90° at increments of 10°, to construct electrode-displacement images and facilitate comparisons with tissue section images. The results revealed that the ablation regions detected using electrode-displacement elastography were highly correlated with those from tissue section images when the angle was between 30° and 60°. However, the boundaries of lesions were difficult to distinguish, when the angle was larger than 60°. The experimental findings suggest that angle selection should be considered to achieve reliable electrode-displacement elastography to describe ablation zones.

TCT-59 Longer term safety and efficacy of sympathetic renal artery denervation using a multi-electrode renal artery denervation catheter in patients with drug-resistant hypertension: Eighteen month results of a first-in-human, multicenter study

Drug-resistant hypertension is a growing problem around the world. Percutaneous sympathetic renal artery denervation is emerging as an approach for the treatment of patients who do not respond adequately to optimal medical therapy. Single-tip electrode radiofrequency ablation catheters have been