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Comparisons between impedance-based and time-based switching bipolar radiofrequency ablation for the treatment of liver cancer. Comput Biol Med 2021; 134:104488. [PMID: 34020132 DOI: 10.1016/j.compbiomed.2021.104488] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 05/06/2021] [Accepted: 05/07/2021] [Indexed: 01/19/2023]
Abstract
Switching bipolar radiofrequency ablation (bRFA) is a cancer treatment technique that activates multiple pairs of electrodes alternately based on a predefined criterion. Various criteria can be used to trigger the switch, such as time (ablation duration) and tissue impedance. In a recent study on time-based switching bRFA, it was determined that a shorter switch interval could produce better treatment outcome than when a longer switch interval was used, which reduces tissue charring and roll-off induced cooling. In this study, it was hypothesized that a more efficacious bRFA treatment can be attained by employing impedance-based switching. This is because ablation per pair can be maximized since there will be no interruption to RF energy delivery until roll-off occurs. This was investigated using a two-compartment 3D computational model. Results showed that impedance-based switching bRFA outperformed time-based switching when the switch interval of the latter is 100 s or higher. When compared to the time-based switching with switch interval of 50 s, the impedance-based model is inferior. It remains to be investigated whether the impedance-based protocol is better than the time-based protocol for a switch interval of 50 s due to the inverse relationship between ablation and treatment efficacies. It was suggested that the choice of impedance-based or time-based switching could ultimately be patient-dependent.
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Abstract
Over the past decade, interventional oncology techniques have become integrated into the treatment plans of companion animals with cancer on a regular basis. Although procedures such as stenting are performed commonly, other less frequently utilized techniques for locoregional therapy, such as embolization and ablation, are emerging and demonstrating promise. Tumor ablation techniques are categorized into two subgroups: chemical ablation and energy-based ablation. Increased utilization of ablation will allow for the determination of specific indications and evaluation of outcomes for these techniques.
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Lehmann KS, Poch FGM, Rieder C, Schenk A, Stroux A, Frericks BB, Gemeinhardt O, Holmer C, Kreis ME, Ritz JP, Zurbuchen U. Minimal vascular flows cause strong heat sink effects in hepatic radiofrequency ablation ex vivo. JOURNAL OF HEPATO-BILIARY-PANCREATIC SCIENCES 2016; 23:508-16. [PMID: 27338856 DOI: 10.1002/jhbp.370] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 06/21/2016] [Indexed: 01/03/2023]
Abstract
BACKGROUND The present paper aims to assess the lower threshold of vascular flow rate on the heat sink effect in bipolar radiofrequency ablation (RFA) ex vivo. METHODS Glass tubes (vessels) of 3.4 mm inner diameter were introduced in parallel to bipolar RFA applicators into porcine liver ex vivo. Vessels were perfused with flow rates of 0 to 1,500 ml/min. RFA (30 W power, 15 kJ energy input) was carried out at room temperature and 37°C. Heat sink effects were assessed in RFA cross sections by the decrease in ablation radius, area and by a high-resolution sector planimetry. RESULTS Flow rates of 1 ml/min already caused a significant cooling effect (P ≤ 0.001). The heat sink effect reached a maximum at 10 ml/min (18.4 mm/s) and remained stable for flow rates up to 1,500 ml/min. CONCLUSIONS Minimal vascular flows of ≥1 ml/min cause a significant heat sink effect in hepatic RFA ex vivo. A lower limit for volumetric flow rate was not found. The maximum of the heat sink effect was reached at a flow rate of 10 ml/min and remained stable for flow rates up to 1,500 ml/min. Hepatic inflow occlusion should be considered in RFA close to hepatic vessels.
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Affiliation(s)
- Kai S Lehmann
- Department of General and Vascular Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Franz G M Poch
- Department of General and Vascular Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Christian Rieder
- Fraunhofer Institute for Medical Image Computing MEVIS, Bremen, Germany
| | - Andrea Schenk
- Fraunhofer Institute for Medical Image Computing MEVIS, Bremen, Germany
| | - Andrea Stroux
- Institute for Biometry and Clinical Epidemiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Bernd B Frericks
- Department of Diagnostic and Interventional Radiology, DRK Kliniken Berlin Westend, Berlin, Germany
| | - Ole Gemeinhardt
- Department of General and Vascular Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Christoph Holmer
- Department of General and Vascular Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Martin E Kreis
- Department of General and Vascular Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Jörg P Ritz
- Department of General and Visceral Surgery, HELIOS Kliniken Schwerin, Schwerin, Germany
| | - Urte Zurbuchen
- Department of General and Vascular Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany
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Lin CC, Cheng YT, Chen M WT, Lin SM. 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. Liver Cancer 2016; 5:8-20. [PMID: 26989656 PMCID: PMC4789949 DOI: 10.1159/000367755] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
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.
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Affiliation(s)
| | | | | | - Shi-Ming Lin
- *Shi-Ming Lin, MD, Division of Hepatology, Liver Research Unit, Department of Gastroenterology, and Hepatology, Chang Gung Memorial Hospital, Lin-Kuo, Chang Gung University, 5, Fu-Hsin St., Kwei-Shan, Taoyuan, Taiwan 333 (ROC), Tel. 886 3 3281200 Ext. 8107, E-Mail
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Pillai K, Al-Alem I, Akhter J, Chua TC, Shehata M, Morris DL. Effect of Nonparallel Placement of In-Circle Bipolar Radiofrequency Ablation Probes on Volume of Tissue Ablated With Heat Sink. Surg Innov 2015; 22:223-234. [DOI: 10.1177/1553350614539047] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023]
Abstract
Objectives. Percutaneous bipolar radiofrequency ablation (RFA) is a minimally invasive technique for treating liver tumors. It is not always possible to insert the bipolar probes parallel to each other on either side of tumor, since it restricts maneuverability away from vital structures or ablate certain tumor shape. Therefore, we investigated how nonparallel placement of probes affected ablation. Methods. Bipolar RFA in parallel and in divergent positions were submerged in tissue model (800 mL egg white) at 37°C and ablated. Temperature probes, T1 and T2 were placed 8.00 mm below the tip of the probes, T3 in between the probe coil elements and T4 and T5 at water inlet and outlet, respectively. Both models with heat sink (+HS) and without (−HS) were investigated. Results. The mean ablated tissue volume, mass, density and height increased linearly with unit angle increase for −HS model. With +HS, a smaller increase in mean volume and mass, a slightly greater increase in mean density but a reduction in height of tissue was seen. The mean ablation time and duration of maximum temperature with +HS was slightly larger, compared with −HS, while −HS ablated at a slightly higher temperature. The heat sink present was minimal for probes in parallel position compared to nonparallel positions. Conclusion. Divergence from parallel insertion of bipolar RFA probes increased the mean volume, mass, and density of tissue ablated. However, the presence of large heat sinks may limit the application of this technique, when tumors border on larger vessels.
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Affiliation(s)
- Krishna Pillai
- University of New South Wales, St. George Hospital, Kogarah, New South Wales, Australia
| | - Ihssan Al-Alem
- University of New South Wales, St. George Hospital, Kogarah, New South Wales, Australia
| | - Javed Akhter
- University of New South Wales, St. George Hospital, Kogarah, New South Wales, Australia
| | - Terence C. Chua
- University of New South Wales, St. George Hospital, Kogarah, New South Wales, Australia
| | - Mena Shehata
- University of New South Wales, St. George Hospital, Kogarah, New South Wales, Australia
| | - David L. Morris
- University of New South Wales, St. George Hospital, Kogarah, New South Wales, Australia
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Dai WC, Cheung TT, Chok KSH, Chan ACY, Sharr WW, Tsang SHY, Yuen WK, Chan SC, Fan ST, Lo CM, Poon RTP. Radiofrequency ablation versus transarterial chemoembolization for unresectable solitary hepatocellular carcinomas sized 5-8 cm. HPB (Oxford) 2015; 17:226-31. [PMID: 25284590 PMCID: PMC4333783 DOI: 10.1111/hpb.12324] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 07/02/2014] [Indexed: 12/12/2022]
Abstract
OBJECTIVES This retrospective review was conducted to compare the efficacy of radiofrequency ablation (RFA) with that of transarterial chemoembolization (TACE) in treating large (5-8 cm) unresectable solitary hepatocellular carcinomas (HCCs). METHODS Patients with large unresectable solitary HCCs primarily treated by RFA or TACE were reviewed. The primary endpoint was overall survival. Secondary endpoints were tumour response, time to disease progression, and treatment-related morbidity and mortality. RESULTS There were 15 patients in the RFA group. Of these, 12 achieved complete ablation, one had ablation site recurrence, and five developed complications. Median disease-free survival in this group was 13.0 months (range: 2.8-38.0 months). The TACE group included 26 patients, of whom four obtained a partial response, none achieved a complete response, and five developed complications. The median time to disease progression in this group was 8.0 months (range: 1.0-68.0 months). There were no hospital deaths in this series. Median survival was 39.8 months in the RFA group and 19.8 months in the TACE group (P = 0.257). Rates of 1-, 2- and 5-year survival were 93.3%, 86.2% and 20.9%, respectively, in the RFA group and 73.1%, 40.6% and 18.3%, respectively, in the TACE group. CONCLUSIONS Both RFA and TACE are feasible treatments for large unresectable solitary HCCs. Both modes show comparable rates of complications and longterm survival, but RFA achieves better initial tumour control and results in better short-term survival.
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Affiliation(s)
- Wing Chiu Dai
- Department of Surgery, Queen Mary Hospital, University of Hong KongHong Kong, China,Correspondence, Wing Chiu Dai, L4, 102 Pok Fu Lam Road, Hong Kong, China. Tel: + 852 2255 3025. Fax: + 852 2816 5284. E-mail:
| | - Tan To Cheung
- Department of Surgery, Queen Mary Hospital, University of Hong KongHong Kong, China
| | - Kenneth S H Chok
- Department of Surgery, Queen Mary Hospital, University of Hong KongHong Kong, China
| | - Albert C Y Chan
- Department of Surgery, Queen Mary Hospital, University of Hong KongHong Kong, China
| | - William W Sharr
- Department of Surgery, Queen Mary Hospital, University of Hong KongHong Kong, China
| | - Simon H Y Tsang
- Department of Surgery, Queen Mary Hospital, University of Hong KongHong Kong, China
| | - Wai Key Yuen
- Department of Surgery, Queen Mary Hospital, University of Hong KongHong Kong, China
| | - See Ching Chan
- Department of Surgery, Queen Mary Hospital, University of Hong KongHong Kong, China
| | - Sheung Tat Fan
- Department of Surgery, Queen Mary Hospital, University of Hong KongHong Kong, China
| | - Chung Mau Lo
- Department of Surgery, Queen Mary Hospital, University of Hong KongHong Kong, China
| | - Ronnie T P Poon
- Department of Surgery, Queen Mary Hospital, University of Hong KongHong Kong, China
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Clinical effectiveness of bipolar radiofrequency ablation for small liver cancers. J Gastroenterol 2013; 48:874-83. [PMID: 23053425 DOI: 10.1007/s00535-012-0685-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Accepted: 09/07/2012] [Indexed: 02/04/2023]
Abstract
BACKGROUND Radiofrequency ablation (RFA) is minimally invasive and can achieve a high rate of cure of liver cancer. This study was conducted to evaluate the efficacy and safety of a bipolar RFA device (CelonPOWER System) in the treatment of Japanese liver cancer patients. METHODS The study was a multicenter, single-group, open-label trial. The indications for RFA were based on the Japanese guidelines for the management of liver cancer. The subjects had a Child-Pugh classification of A or B, and the target tumors were defined as nodular, numbering up to 3 lesions, each of which was 3 cm or less in diameter, or solitary lesions up to 4 cm in diameter. To test for the non-inferiority of the CelonPOWER System, this system was compared with the Cool-tip RF System, which has already been approved in Japan, in terms of the complete necrosis rate (CNR). RESULTS The CNR obtained with the CelonPOWER System was 97.8 % (88/90 patients). The CNR obtained with the Cool-tip RF System was 86.2 % (50/58 patients), confirming the non-inferiority of the CelonPOWER System (p < 0.001, Fisher's exact test based on binomial distribution). Throughout the treatment and follow-up periods, there were no adverse events regarding safety that were uniquely related to the CelonPOWER System and there were no cases of device failure. CONCLUSIONS The CelonPOWER System was confirmed to be an effective and safe RFA device. It could become extensively used as a safe next-generation RFA device, reducing the physical burden on patients.
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Yoon JH, Lee JM, Han JK, Choi BI. Dual switching monopolar radiofrequency ablation using a separable clustered electrode: comparison with consecutive and switching monopolar modes in ex vivo bovine livers. Korean J Radiol 2013; 14:403-11. [PMID: 23690705 PMCID: PMC3655292 DOI: 10.3348/kjr.2013.14.3.403] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 12/26/2012] [Indexed: 01/19/2023] Open
Abstract
Objective To compare the in-vitro efficiency of dual-switching monopolar (DSM) radiofrequency ablation (RFA) using a separable clustered electrode (Octopus® electrodes) with consecutive monopolar (CM) and switching monopolar (SM) RFA techniques to create an ablative zone in the explanted bovine liver. Materials and Methods For DSM-RFA, we used a prototype, three-channel, dual generator RFA Unit and Octopus® electrodes with three, 17 gauge internally cooled electrodes. The RFA Unit allowed simultaneous radiofrequency (RF) energy delivery to two electrodes of the Octopus® electrodes as well as automatic switching among the three electrode pairs according to the impedance changes. RF energy was sequentially applied to one of the three electrodes for 24 minutes (group A; CM mode, n = 10) or alternatively applied for 12 minutes (group B; SM mode, n = 10) or concurrently applied to a pair of electrodes for 12 minutes (group C; DSM mode, n = 10) in explanted bovine livers. Changes in the impedance and current during RFA as well as the dimensions of the thermal ablative zones were compared among the three groups. Results The mean, delivered RF energy amounts in groups A, B, and C were 63.15 ± 8.6 kJ, 72.13 ± 5.4 kJ, and 106.08 ± 13.4 kJ, respectively (p < 0.001). The DSM mode created a significantly larger ablation volume than did the other modes, i.e., 68.1 ± 10.2 cm3 (group A), 92.0 ± 19.9 cm3 (group B), and 115.1 ± 14.0 cm3 (group C) (p < 0.001). The circularity in groups A, B, and C were 0.84 ± 0.06, 0.87 ± 0.04 and 0.90 ± 0.03, respectively (p = 0.03). Conclusion DSM-RFA using Octopus® electrodes can help create large ablative zones within a relatively short time.
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Affiliation(s)
- Jeong-Hee Yoon
- Department of Radiology, Seoul National University College of Medicine, Seoul 110-744, Korea
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9
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Baldwin K, Katz SC, Rubin A, Somasundar P. Bipolar radiofrequency ablation of liver tumors: Technical experience and interval follow-up in 22 patients with 33 ablations. J Surg Oncol 2012; 106:905-10. [DOI: 10.1002/jso.23147] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Accepted: 04/16/2012] [Indexed: 02/06/2023]
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Kasivisvanathan V, Thapar A, Oskrochi Y, Picard J, Leen ELS. Irreversible electroporation for focal ablation at the porta hepatis. Cardiovasc Intervent Radiol 2012; 35:1531-4. [PMID: 22367010 DOI: 10.1007/s00270-012-0363-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Accepted: 02/06/2012] [Indexed: 12/17/2022]
Abstract
Patients with chemotherapy-refractory liver metastases who are not candidates for surgery may be treated with focal ablation techniques with established survival benefits. Irreversible electroporation is the newest of these and has the putative advantages of a nonthermal action, preventing damage to adjacent biliary structures and bowel. This report describes the use of irreversible electroporation in a 61-year-old man with a solitary chemoresistant liver metastasis unsuitable for radiofrequency ablation as a result of its proximity to the porta hepatis. At 3 months, tumor size was decreased on computed tomography from 28 × 19 to 20 × 17 mm, representing stable disease according to the response evaluation criteria in solid tumors. This corresponded to a decrease in tumor volume size from 5.25 to 3.16 cm(3). There were no early or late complications. Chemoresistant liver metastases in the proximity of the porta hepatis that are considered to be too high a risk for conventional surgery or thermal ablation may be considered for treatment by the novel ablation technique of irreversible electroporation.
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Ritz JP, Lehmann KS, Schumann T, Knappe V, Zurbuchen U, Buhr HJ, Holmer C. Effectiveness of various thermal ablation techniques for the treatment of nodular thyroid disease--comparison of laser-induced thermotherapy and bipolar radiofrequency ablation. Lasers Med Sci 2011; 26:545-52. [PMID: 21455786 DOI: 10.1007/s10103-011-0907-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Accepted: 03/01/2011] [Indexed: 12/18/2022]
Abstract
Alternative minimally invasive treatment options such as radiofrequency ablation (RFA) or laser-induced thermotherapy (LITT) are at present under investigation for achieving a nonsurgical targeted cytoreduction in benign and malignant thyroid lesions. So far, studies have not been able to show a secure advantage for neither LITT nor RFA. The aim of this study was to compare the two ablation procedures in terms of their effectiveness. Thermal lesions were induced in porcine thyroid glands either by LITT or bipolar RFA ex vivo (n = 110 each) and in vivo (n = 10 each) using power settings between 10 and 20 W. Temperature spread during application was documented in 5- and 10-mm distance of the applicator. Postinterventional lesion diameters were measured and lesion size was calculated. Furthermore, enzyme histochemical analysis of the thyroid tissue was performed in vivo. Lesion volumes induced by LITT ranged between 0.74 ± 0.18 cm(3) (10 W) and 3.80 ± 0.41 cm(3) (20 W) with a maximum of 5.13 ± 0.16 cm(3) at 18 W. The inducible lesion volumes by RFA were between 2.43 ± 0.68 cm(3) (10 W) and 0.91 ± 0.71 cm(3) (20 W) with a maximum of 2.80 ± 0.85 cm(3) at 14 W. The maximum temperatures were 112.9 ± 9.2°C (LITT) and 61.6 ± 13.9°C (RFA) at a distance of 5 mm and 73.2 ± 6.7°C (LITT) and 53.5 ± 8.6°C (RFA) at a distance of 10 mm. The histochemical analysis demonstrates a complete loss of NADPH dehydrogenase activity in thermal lesions as a sign of irreversible cell damage both for LITT and RFA. This study is the first to compare the effectiveness of laser-induced thermotherapy and radiofrequency ablation of thyroid tissue. LITT as well as RFA are suitable for singular thyroid nodules and induces reproducible clinically relevant lesions in an appropriate application time. The maximum inducible lesion volumes by LITT are significantly larger than by RFA with the devices used herein.
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Affiliation(s)
- Jörg-Peter Ritz
- Department of General, Vascular and Thoracic Surgery, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Hindenburgdamm 30, 12200, Berlin, Germany
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Ahmed M, Brace CL, Lee FT, Goldberg SN. Principles of and advances in percutaneous ablation. Radiology 2011; 258:351-69. [PMID: 21273519 DOI: 10.1148/radiol.10081634] [Citation(s) in RCA: 533] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Image-guided tumor ablation with both thermal and nonthermal sources has received substantial attention for the treatment of many focal malignancies. Increasing interest has been accompanied by continual advances in energy delivery, application technique, and therapeutic combinations with the intent to improve the efficacy and/or specificity of ablative therapies. This review outlines clinical percutaneous tumor ablation technology, detailing the science, devices, techniques, technical obstacles, current trends, and future goals in percutaneous tumor ablation. Methods such as chemical ablation, cryoablation, high-temperature ablation (radiofrequency, microwave, laser, and ultrasound), and irreversible electroporation will be discussed. Advances in technique will also be covered, including combination therapies, tissue property modulation, and the role of computer modeling for treatment optimization.
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Affiliation(s)
- Muneeb Ahmed
- Laboratory for Minimally Invasive Tumor Therapy, Section of Interventional Radiology, and Section of Abdominal Imaging, Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, 1 Deaconess Rd, Boston, MA 02215, USA.
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Peng ZW, Liang HH, Chen MS, Zhang YJ, Zhang YQ, Lau WY. Conformal radiofrequency ablation of hepatocellular carcinoma with a multi-pin bipolar system. J Surg Oncol 2011; 103:69-74. [PMID: 21031425 DOI: 10.1002/jso.21742] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
BACKGROUND To retrospectively evaluate the effectiveness and safety of radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC) with a multi-pin bipolar system. METHODS Between August 2005 and December 2006, 18 patients with 30 HCCs (3.40 ± 1.24 cm, range 1.30-6.0 cm; median number of treated lesions is two per patient, range, 1-3) underwent percutaneous RFA with a multi-pin bipolar system under ultrasound guidance. The primary end-point were treatment efficacy, major and minor complications, and the secondary end-point were overall survival and tumor-free survival. RESULTS Complete ablation with conformed shape to the index tumor was achieved in 16 of 18 patients, and 28 of the 30 tumors were completely ablated. On follow-up, local and distant intrahepatic tumor progression rates were 12.5% (2 of 16 patients) and 62.5% (10 of 16 patients). There was no patient who developed extrahepatic metastasis. There were no major complications. The 1-, 2-year overall survival rates for all patients were 83.3%, 55.6%, respectively, and the corresponding tumor-free survivals were 50.0%, 22.2%, respectively. CONCLUSION RFA with a multi-pin bipolar system was effective and safe for HCC. A large ablation volume could be achieved which conformed to the shape of the index tumor.
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Affiliation(s)
- Zhen-Wei Peng
- Department of Hepatobiliary Surgery, Cancer Centre of Sun Yat-Sen University, Guangzhou, China
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Abstract
BACKGROUND Intraoperative radiofrequency ablation (IRFA) of liver metastases can be used to treat patients with complex tumours that are unsuitable for parenchymal resection alone. This systematic review assesses the frequency, patterns and severity of complications associated with this procedure. METHODS We carried out a bibliographic search on MEDLINE focused on IRFA for liver metastases, excluding hepatocarcinomas, and on intraoperative use, excluding percutaneous application. RESULTS Thirty papers published between 1999 and 2007 were analysed. They covered a total of 2822 patients and 1755 IRFA procedures. The indications and techniques for IRFA differ from those for percutaneous treatment, as do associated results and complications. Specific complications associated with IRFA, such as liver abscesses, biliary stenoses and vascular thromboses, are directly correlated with the indications and associated procedures. Published results should be interpreted with caution as IRFA can be used alone or combined with parenchymal resection. CONCLUSIONS Specific complications related to IRFA are rare, especially for lesions of <35 mm in size located far from a main biliary duct, when additional septic procedures are not used. A lesion-by-lesion approach based on the benefit : risk ratio should therefore be used in the process of making surgical decisions. Combining resection with IRFA leads to higher morbidity, especially in difficult patients with numerous bilateral lesions, but may be necessary to achieve R0 (microscopically negative margins) outcomes.
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Affiliation(s)
| | - Milène Isambert
- Digestive Tumours Unit, Institute Bergonie (Institut Bergonié)Bordeaux, France,Faculty of Medicine, University of BordeauxBordeaux, France
| | - Serge Evrard
- Digestive Tumours Unit, Institute Bergonie (Institut Bergonié)Bordeaux, France,Faculty of Medicine, University of BordeauxBordeaux, France
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Radiofrequency ablation of large size liver tumours using novel plan-parallel expandable bipolar electrodes: initial clinical experience. Eur J Radiol 2009; 77:167-71. [PMID: 19616911 DOI: 10.1016/j.ejrad.2009.06.025] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2009] [Accepted: 06/22/2009] [Indexed: 02/06/2023]
Abstract
PURPOSE Although radiofrequency ablation (RFA) is a promising method for local treatment of liver malignancies, with conventional monopolar systems recurrence rates for large size tumours (≥3.5 cm) remain high. The objective of this study was to evaluate the safety, feasibility and local effectiveness of a novel bipolar plan-parallel expandable system for these larger tumours. METHODS AND MATERIALS Eight consecutive patients with either unresectable colorectal liver metastases (CRLM in 6 patients), carcinoid liver metastases (1 patient) and hepatocellular carcinoma (HCC in 1 patient) of ≥3.5 cm were treated with bipolar RFA during laparotomy with ultrasound guidance. Early and late, major and minor complications were recorded. Local success was determined on 3-8 month follow-up CT scans of the upper abdomen. RESULTS Nine CRLM, one carcinoid liver metastases and one HCC (3.5-6.6 cm) were ablated with bipolar RFA. Average ablation time was 16 min (range 6-29 min.). Two patients developed a liver abscess which required re-laparotomy. In both cases bowel surgery during the same session probably caused bacterial spill. There were no mortalities. The patients were released from hospital between 5 and 29 days after the procedure (median 12 days). The 6-12 month follow-up PET-CT scans showed signs for marginal RFA-site tumour recurrence in three patients with CRLM (3/11 lesions). CONCLUSION Preliminary results suggest bipolar RFA to be a reasonably safe, fast and feasible technique which seems to improve local control for large size hepatic tumour ablations.
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16
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Ex situ quantification of the cooling effect of liver vessels on radiofrequency ablation. Langenbecks Arch Surg 2009; 394:475-81. [DOI: 10.1007/s00423-009-0480-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Accepted: 02/25/2009] [Indexed: 10/21/2022]
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Seror O, N'Kontchou G, Ibraheem M, Ajavon Y, Barrucand C, Ganne N, Coderc E, Trinchet JC, Beaugrand M, Sellier N. Large (>or=5.0-cm) HCCs: multipolar RF ablation with three internally cooled bipolar electrodes--initial experience in 26 patients. Radiology 2008; 248:288-96. [PMID: 18483229 DOI: 10.1148/radiol.2481071101] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
PURPOSE To prospectively evaluate the safety and effectiveness of percutaneous multipolar radiofrequency (RF) ablation for the treatment of large (>or=5.0 cm in diameter) hepatocellular carcinomas (HCCs). MATERIALS AND METHODS Twenty-six patients (four women, 22 men; median age, 72 years) with cirrhosis (Child-Pugh class A disease, 22 patients; Child-Pugh class B disease, four patients) and at least one 5.0-9.0-cm-diameter HCC without invasion of the portal trunk or main portal branches were treated with multipolar RF ablation performed by a single operator. The procedure was performed with three separate bipolar linear internally cooled electrodes with ultrasonographic guidance. Twenty-seven of the 33 tumors treated had a diameter of 5.0 cm or greater (median diameter, 5.7 cm; range, 5.0-8.5 cm); 12 of these 27 tumors were infiltrative, and four invaded segmental portal vein branches. Ten patients had a serum alpha-fetoprotein level higher than 400 microg/L. Results were assessed by using computed tomography. Primary effectiveness, complications, tumor progression, and survival rates were recorded. Probabilities of survival were calculated by using the Kaplan-Meier method. RESULTS One to two RF ablation procedures per patient (mean, 1.15 +/- 0.43 [standard deviation]) led to the complete ablation of 22 (81%) of the 27 tumors (18 tumors after one and four tumors after two procedures), including three tumors that showed segmental portal vein invasion. All patients experienced postablation syndrome, and one experienced subcapsular hematoma and a segmental liver infarct, but no major complication occurred. After a mean follow-up of 14 months (range, 3-34 months), local and distant tumor progression and actual survival rates were 14% (three of 22), 24% (five of 21), and 65% (17 of 26), respectively. The probabilities of 1- and 2-year survival, respectively, were 68% (95% confidence interval: 49%, 86%) and 56% (95% confidence interval: 51%, 81%). CONCLUSION HCCs larger than 5.0 cm (but smaller than 9.0 cm)--even those that are infiltrative and those that involve a segmental portal vein--can be completely and safely ablated with multipolar RF ablation.
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Affiliation(s)
- Olivier Seror
- Department of Radiology, Centre Hôspitalo-Universitaire Jean Verdier, Assistance Publique-Hôpitaux de Paris, avenue du 14 Juillet, 93140 Bondy, France.
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18
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Lee JM, Han JK, Kim SH, Son KR, Kim HC, Kim SJ, Choi BI. In Vivo Efficiency of Multipolar Radiofrequency Ablation with Two Bipolar Electrodes: A Comparative Experimental Study in Pig Kidney. J Vasc Interv Radiol 2007; 18:1553-60. [DOI: 10.1016/j.jvir.2007.08.029] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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MESH Headings
- Bone Neoplasms/diagnostic imaging
- Bone Neoplasms/secondary
- Bone Neoplasms/surgery
- Carcinoma, Hepatocellular/diagnostic imaging
- Carcinoma, Hepatocellular/surgery
- Carcinoma, Non-Small-Cell Lung/diagnostic imaging
- Carcinoma, Non-Small-Cell Lung/surgery
- Carcinoma, Renal Cell/diagnostic imaging
- Carcinoma, Renal Cell/surgery
- Cryosurgery/methods
- Electrocoagulation/methods
- Fluoroscopy
- Humans
- Image Processing, Computer-Assisted
- Imaging, Three-Dimensional
- Kidney Neoplasms/diagnostic imaging
- Kidney Neoplasms/surgery
- Liver Neoplasms/diagnostic imaging
- Liver Neoplasms/secondary
- Liver Neoplasms/surgery
- Lung Neoplasms/diagnostic imaging
- Lung Neoplasms/secondary
- Lung Neoplasms/surgery
- Neoplasms/diagnostic imaging
- Neoplasms/surgery
- Osteoma, Osteoid/diagnostic imaging
- Osteoma, Osteoid/surgery
- Radiology, Interventional
- Tomography, X-Ray Computed
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Affiliation(s)
- Michael Beland
- Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
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Isbert C, Buhr HJ, Ritz JP, Hohenberger W, Germer CT. Curative in situ ablation of colorectal liver metastases-experimental and clinical implementation. Int J Colorectal Dis 2007; 22:705-15. [PMID: 17131150 DOI: 10.1007/s00384-006-0231-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/13/2006] [Indexed: 02/04/2023]
Abstract
INTRODUCTION In situ ablation of colorectal liver metastases is frequently assessed for palliative treatment only. The establishment of clinically relevant lesion size and a lack of long-term survival data were regarded as main limitations to using them with curative intention. In contrast to surgical liver resection, whose oncological findings seem to have remained unchanged over the years, the in situ ablation methods have considerably changed technically and clinically in the last few years. OBJECTIVE The aim of the paper was to point out experimental and clinical data underlining the impact of in situ ablation for potentially curative treatment of colorectal liver metastases. DISCUSSION On the basis of experimental data, the aim of complete local tumor control (R0 ablation) can only be obtained if additional energy is applied after reaching the tumor-adapted maximal coagulation volume. Analogous to the oncological safety margin in surgical resection, we defined this decisive energy difference as the "energy safety margin" for in situ ablation. The energy safety margin is the energy that must be additionally applied after reaching the plateau in the energy/volume curve to achieve complete tumor coagulation. In addition to that, in situ ablation should be combined with temporary interruption of hepatic perfusion whenever possible to prevent intralesional recurrences. In this way, the thermoprotective mechanism of hepatic perfusion can be effectively eliminated. With restrictions, the survival data after ablation in specialized centers is comparable to surgical resection with concomitantly lower morbidity and mortality. Based on recent findings and with the corresponding expertise in the field of ablation and state-of-the-art equipment, ablation is, thus, an alternative to surgical resection. The combined application of surgical resection and ablation is also a suitable method for increasing the R0 rate and thus helps improve the prognosis of treated patients. In summary, it can be said that in situ ablation is a useful expansion of the therapeutic spectrum of liver metastases and can be applied as an alternative to or in combination with surgical resection.
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Affiliation(s)
- Christoph Isbert
- Department of General, Visceral and Thoracic Surgery, Klinikum Nuernberg Nord, Prof.-Ernst-Nathan-Str.1, 90419, Nuernberg, Germany.
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21
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Isbert C, Ritz JP, Roggan A, Schuppan D, Ajubi N, Buhr HJ, Hohenberger W, Germer CT. Laser-induced thermotherapy (LITT) elevates mRNA expression of connective tissue growth factor (CTGF) associated with reduced tumor growth of liver metastases compared to hepatic resection. Lasers Surg Med 2007; 39:42-50. [PMID: 17111416 DOI: 10.1002/lsm.20448] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND OBJECTIVES Proliferation and synthesis of hepatocellular tissue after tissue damage are promoted by specific growth factors such as hepatic tissue growth factor (HGF) and connective growth factor (CTGF). Laser-induced thermotherapy (LITT) for the treatment of liver metastases is deemed to be a parenchyma-saving procedure compared to hepatic resection. The aim of this study was to compare the impact of LITT and hepatic resection on intrahepatic residual tumor tissue and expression levels of mRNA HGF/CTGF within liver and tumor tissue. STUDY DESIGN/MATERIALS AND METHODS Two independent adenocarcinomas (CC531) were implanted into 75 WAG rats, one in the right (untreated tumor) and one in the left liver lobe (treated tumor). The left lobe tumor was treated either by LITT or partial hepatectomy. The control tumor was submitted to in-situ hybridization of HGF and CTGF 24-96 hours and 14 days after intervention. RESULTS Volumes of the untreated tumors prior to intervention were 38+/-8 mm(3) in group I (laser), 39 +/- 7 mm(3) in group II (resection), and 42 +/- 12 mm(3) in group III (control) and did not differ significantly (P > 0.05). Fourteen days after the intervention the mean tumor+/-SEM volume of untreated tumor in group I (laser) [223 +/- 36] was smaller than in group II (resection) [1233.28 +/- 181.52; P < 0.001], and in group III (control) [978.92 +/- 87.57; P < 0.003]. Forty-eight hours after the intervention intrahepatic mRNA expression level of HGF in group II (resection) was almost twofold higher than in group I (laser) [7.2 +/- 1.0 c/mf vs. 3.9 +/- 0.4 c/mf; P<0.01]. Fourteen days after the intervention intrahepatic mRNA expression level of CTGF in group I (laser) was higher than in group II (resection) [13.89 +/- 0.77 c/mf vs. 9.09 +/- 0.78 c/mf; P < 0.003]. CONCLUSIONS LITT leads to a decrease of residual tumor growth in comparison to hepatic resection. Accelerated tumor growth after hepatic resection is associated with higher mRNA level of HGF and reduced tumor growth after LITT with higher mRNA level of CTGF. The increased CTGF-mediated regulation of ECM may cause reduced residual tumor growth after LITT.
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Affiliation(s)
- Christoph Isbert
- Department of Surgery, Klinikum Nuernberg Nord, D-90419 Nuernberg, Germany.
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Ritz JP, Lehmann KS, Zurbuchen U, Wacker F, Brehm F, Isbert C, Germer CT, Buhr HJ, Holmer C. Improving laser-induced thermotherapy of liver metastases--effects of arterial microembolization and complete blood flow occlusion. Eur J Surg Oncol 2007; 33:608-15. [PMID: 17400421 DOI: 10.1016/j.ejso.2007.02.028] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2006] [Accepted: 02/20/2007] [Indexed: 02/07/2023] Open
Abstract
INTRODUCTION A prerequisite for an oncologically curative application of laser-induced thermotherapy (LITT) of liver metastases is complete tumor destruction. This increased effectiveness was achieved experimentally by combining LITT with interrupted hepatic perfusion. The aim of this study was to evaluate whether an interventional selective arterial microembolization might be as effective as complete blood flow occlusion using an open Pringle's maneuver. PATIENTS AND METHODS We included patients with unresectable colorectal liver metastases. LITT was performed without interrupted hepatic perfusion (control group) compared to LITT in combination with interrupted perfusion either by embolization of intraarterial degradable starch microspheres (DSM) (percutaneous access) or by complete hepatic inflow occlusion (Pringle's maneuver; open access). Online monitoring was performed using intraoperative ultrasound or MRI. Volumetric techniques were used to assess metastases and postinterventional lesions. RESULTS Fifty-six patients with 104 metastases (control group (25), DSM (37), and Pringle (42)) were treated. The preinterventional tumor volumes were significantly smaller than the postinterventional lesion volumes (control group: 9.8 vs. 25.3 cm3; DSM: 9.5 vs. 65.4 cm3; Pringle: 12.9 vs. 76.5 cm3). The morbidity rate was 21.4% without treatment-related mortalities. After 6 months follow-up, tumor recurrence was diagnosed in 6 patients (control group (4), LITT with DSM (1), and Pringle (1)). CONCLUSIONS Combining LITT with blood flow occlusion leads to a significant increase in lesion size. The application of DSM offers a safe and effective alternative to the open access with Pringle's maneuver. Compared to LITT-monotherapy, this modality achieves significantly larger thermal lesions with the need of fewer applications.
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Affiliation(s)
- J-P Ritz
- Department of General, Vascular and Thoracic Surgery, Charité - University Medicine Berlin, Campus Benjamin Franklin, Hindenburgdamm 30, 12200 Berlin, Germany
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González HD, Figueras J. Practical questions in liver metastases of colorectal cancer: general principles of treatment. HPB (Oxford) 2007; 9:251-8. [PMID: 18345300 PMCID: PMC2215392 DOI: 10.1080/13651820701457992] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2007] [Indexed: 12/12/2022]
Abstract
Liver metastases of colorectal cancer are currently treated by multidisciplinary teams using strategies that combine chemotherapy, surgery and ablative techniques. Many patients classically considered non-resectable can now be rescued by neoadjuvant chemotherapy followed by liver resection, with similar results to those obtained in initial resections. While many of those patients will recur, repeat resection is a feasible and safe approach if the recurrence is confined to the liver. Several factors that until recently were considered contraindications are now recognized only as adverse prognostic factors and no longer as contraindications for surgery. The current evaluation process to select patients for surgery is no longer focused on what is to be removed but rather on what will remain. The single most important objective is to achieve a complete (R0) resection within the limits of safety in terms of quantity and quality of the remaining liver. An increasing number of patients with synchronous liver metastases are treated by simultaneous resection of the primary and the liver metastatic tumours. Multilobar disease can also be approached by staged procedures that combine neoadjuvant chemotherapy, limited resections in one lobe, embolization or ligation of the contralateral portal vein and a major resection in a second procedure. Extrahepatic disease is no longer a contraindication for surgery provided that an R0 resection can be achieved. A reverse surgical staged approach (liver metastases first, primary second) is another strategy that has appeared recently. Provided that a careful selection is made, elderly patients can also benefit from surgical treatment of liver metastases.
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Affiliation(s)
- Héctor Daniel González
- Division of Hepatobiliary and Pancreatic Surgery, Department of Surgery, Hospital Josep TruetaGironaSpain
| | - Joan Figueras
- Division of Hepatobiliary and Pancreatic Surgery, Department of Surgery, Hospital Josep TruetaGironaSpain
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Lee JM, Han JK, Lee JY, Kim SH, Choi JY, Lee MW, Choi SH, Eo H, Choi BI. Hepatic radiofrequency ablation using multiple probes: ex vivo and in vivo comparative studies of monopolar versus multipolar modes. Korean J Radiol 2006; 7:106-17. [PMID: 16799271 PMCID: PMC2667583 DOI: 10.3348/kjr.2006.7.2.106] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2005] [Accepted: 12/16/2005] [Indexed: 02/06/2023] Open
Abstract
OBJECTIVE We wanted to compare the efficiency of multipolar radiofrequency ablation (RFA) using three perfused-cooled electrodes with multiple overlapping and simultaneous monopolar techniques for creating an ablation zone in ex vivo bovine livers and in in vivo porcine livers. MATERIALS AND METHODS In the ex vivo experiments, we used a 200 W generator (Valleylab, CC-3 model) and three perfused-cooled electrodes or internally cooled electrodes to create 30 coagulation zones by performing consecutive monopolar RFA (group A, n = 10), simultaneous monopolar RFA (group B, n = 10) or multipolar RFA (group C, n = 10) in explanted bovine livers. In the consecutive mode, three ablation spheres were created by sequentially applying 150 watts radiofrequency (RF) energy to the internally cooled electrodes for 12 minutes each for a total of 36 minutes. In the simultaneous monopolar and multipolar modes, RF energy was concurrently applied to the three perfused-cooled electrodes for 20 minutes at 150 watt with instillation of 6% hypertonic saline at 2 mL/min. During RFA, we measured the temperatures of the treated area at its center. The changes in impedance, the current and liver temperature during RFA, as well as the dimensions of the thermal ablation zones, were compared among the three groups. In the in vivo experiments, three coagulations were created by performing multipolar RFA in a pig via laparotomy with using same parameter as the ex vivo study. RESULTS In the ex vivo experiments, the impedance was gradually decreased during the RFA in groups B and C, but in group A, the impedance was increased during RFA and this induced activation by the pulsed RF technique. In groups A, B and C, the mean final-temperature values were 80+/-10 degrees C, 69+/-18 degrees C and 79+/-12 degrees C, respectively (p < 0.05). The multipolar mode created a larger volume of ablation than did the other modes: 37.6+/-4.0 cm3 (group A); 44.9+/-12.7 cm3 (group B); and 78.9+/-6.9 cm3 (group C) (p < 0.05). In the in vivo experiment, the pig well tolerated the RFA procedure and no major complications occurred during the 4 days of the follow-up period. The mean volume of coagulations produced by multipolar RFA in the pig liver was 60.5+/-17.9 cm3. CONCLUSION For the multiple probe RFA, the multipolar mode with hypertonic saline instillation was more efficient in generating larger areas of thermal ablation than either the consecutive or simultaneous monopolar modes.
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Affiliation(s)
- Jeong Min Lee
- Department of Radiology, and Institute of Radiation Medicine, Seoul National University College of Medicine; Clinical Research Institute, Seoul National University Hospital, Seoul 110-744, Korea
| | - Joon Koo Han
- Department of Radiology, and Institute of Radiation Medicine, Seoul National University College of Medicine; Clinical Research Institute, Seoul National University Hospital, Seoul 110-744, Korea
| | - Jae Young Lee
- Department of Radiology, and Institute of Radiation Medicine, Seoul National University College of Medicine; Clinical Research Institute, Seoul National University Hospital, Seoul 110-744, Korea
| | - Se Hyung Kim
- Department of Radiology, and Institute of Radiation Medicine, Seoul National University College of Medicine; Clinical Research Institute, Seoul National University Hospital, Seoul 110-744, Korea
| | - Jin Young Choi
- Department of Radiology, and Institute of Radiation Medicine, Seoul National University College of Medicine; Clinical Research Institute, Seoul National University Hospital, Seoul 110-744, Korea
| | - Min Woo Lee
- Department of Radiology, and Institute of Radiation Medicine, Seoul National University College of Medicine; Clinical Research Institute, Seoul National University Hospital, Seoul 110-744, Korea
| | - Seung Hong Choi
- Department of Radiology, and Institute of Radiation Medicine, Seoul National University College of Medicine; Clinical Research Institute, Seoul National University Hospital, Seoul 110-744, Korea
| | - Hong Eo
- Department of Radiology, and Institute of Radiation Medicine, Seoul National University College of Medicine; Clinical Research Institute, Seoul National University Hospital, Seoul 110-744, Korea
| | - Byung Ihn Choi
- Department of Radiology, and Institute of Radiation Medicine, Seoul National University College of Medicine; Clinical Research Institute, Seoul National University Hospital, Seoul 110-744, Korea
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