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Neizert CA, Do HNC, Zibell M, Sinden D, Rieder C, Albrecht J, Niehues SM, Lehmann KS, Poch FGM. Optimizing microwave ablation planning with the ablation success ratio. Sci Rep 2025; 15:10450. [PMID: 40140611 PMCID: PMC11947081 DOI: 10.1038/s41598-025-94957-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2024] [Accepted: 03/18/2025] [Indexed: 03/28/2025] Open
Abstract
The size of hepatic microwave ablations (MWA) is often difficult to predict due to cooling effects from liver vessels. This study introduces a simplified predictive model, the Ablation Success Ratio (ASR), which estimates the likelihood of a successful ablation based on tumor size and specific ablation parameters. The ASR model is based on the three-dimensional minimum ablation radius (r3Dmin), defining the spherical region within which complete ablation is achieved. To validate the ASR, standardized MWAs were performed in an ex vivo porcine liver model using a glass tube to simulate the vascular cooling effect. Ablations (n = 148) were conducted at 100 W for 5 min, with antenna-to-vessel (A-V) distances set at 2.5, 5.0, and 10.0 mm. Subsequently, the r3Dmin was calculated. Without vascular cooling (0 ml/min, corresponding to an intraoperative Pringle maneuver), an ASR of 100% was achieved for ablation diameters up to 20 mm. However, in the presence of vascular cooling (1-500 ml/min), the ASR reached 100% only for ablation diameters up to 12 mm, demonstrating that the ASR effectively includes the impact of vascular cooling effects. The ASR is a promising and simple approach for predicting ablation success while also accounting for vascular cooling effects in hepatic MWA.
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Affiliation(s)
- Christina A Neizert
- Department of General and Visceral Surgery, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Hindenburgdamm 30, 12203, Berlin, Germany.
| | - Hoang N C Do
- Department of General and Visceral Surgery, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Hindenburgdamm 30, 12203, Berlin, Germany
| | - Miriam Zibell
- Landesamt für Gesundheit und Soziales, Turmstraße 21, 10559, Berlin, Germany
| | - David Sinden
- Fraunhofer Institute for Digital Medicine MEVIS, Max-Von-Laue-Straße 2, 28359, Bremen, Germany
| | - Christian Rieder
- Fraunhofer Institute for Digital Medicine MEVIS, Max-Von-Laue-Straße 2, 28359, Bremen, Germany
| | - Jakob Albrecht
- Department of General and Visceral Surgery, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Hindenburgdamm 30, 12203, Berlin, Germany
| | - Stefan M Niehues
- Department of Radiology, Caritas-Klinik Dominikus, Kurhausstraße 30, 13467, Berlin, Germany
| | - Kai S Lehmann
- Department of General and Visceral Surgery, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Hindenburgdamm 30, 12203, Berlin, Germany
| | - Franz G M Poch
- Department of General and Visceral Surgery, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Hindenburgdamm 30, 12203, Berlin, Germany
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Cai H, Shan G, Wei Z, Zhao W, Xue G, Zhang C, Ye X. Guidelines for power and time variables for microwave ablation in porcine lung in vitro. J Cancer Res Ther 2024; 20:1150-1156. [PMID: 39206976 DOI: 10.4103/jcrt.jcrt_817_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Accepted: 06/29/2023] [Indexed: 09/04/2024]
Abstract
PURPOSE Determination of the appropriate ablative parameters is the key to the success and safety of microwave ablation (MWA) of lung tumors. The purpose of this study was to provide guidelines and recommendations for the optimal time and power for lung tumor MWA. MATERIAL AND METHODS MWA using a 2450-MHz system was evaluated in a porcine lung. The independent variables were power (30, 40, 50, 60, 70, and 80 W) and time (2, 4, 6, 8, 10, and 12 min), and the outcome variable was the volume of ablation. Lung tissues were procured after MWA for measurement and histological evaluation. Analysis of variance was used for statistical analysis, followed by least significant difference (LSD) t-tests where appropriate. A P value of <0.05 was considered statistically significant. RESULTS The outcome variable (ablative volume) was significantly affected by time, power, and time/power interaction (P < 0.05). When the total output energy was kept constant, the combination of higher power and shorter time obtained a larger ablative volume, especially in the low- and medium-energy groups (P < 0.01). CONCLUSIONS We propose guidelines for ablative volume based on different time and power variables to provide a reference for clinical applications.
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Affiliation(s)
- Hongchao Cai
- Department of Oncology, The First Affiliated Hospital of Shandong First Medical University and Shandong Provincial Qianfoshan Hospital, Shandong Lung Cancer Institute, Shandong Key Laboratory of Rheumatic Disease and Translational Medicine, Jinan, Shandong Province, China No. 16766, Jingshi Road, Jinan, Shandong Province, China
| | - Guanglian Shan
- Department of Oncology, People's Hospital of Xintai City, China No. 1329, Xinpu Road, Xintai, Shandong Province, China
| | - Zhigang Wei
- Department of Oncology, The First Affiliated Hospital of Shandong First Medical University and Shandong Provincial Qianfoshan Hospital, Shandong Lung Cancer Institute, Shandong Key Laboratory of Rheumatic Disease and Translational Medicine, Jinan, Shandong Province, China No. 16766, Jingshi Road, Jinan, Shandong Province, China
| | - Wenhua Zhao
- Department of Oncology, The First Affiliated Hospital of Shandong First Medical University and Shandong Provincial Qianfoshan Hospital, Shandong Lung Cancer Institute, Shandong Key Laboratory of Rheumatic Disease and Translational Medicine, Jinan, Shandong Province, China No. 16766, Jingshi Road, Jinan, Shandong Province, China
| | - Guoliang Xue
- Department of Oncology, The First Affiliated Hospital of Shandong First Medical University and Shandong Provincial Qianfoshan Hospital, Shandong Lung Cancer Institute, Shandong Key Laboratory of Rheumatic Disease and Translational Medicine, Jinan, Shandong Province, China No. 16766, Jingshi Road, Jinan, Shandong Province, China
| | - Chao Zhang
- Department of Oncology, Affiliated Qujing Hospital of Kunming Medical University, Qujing, Yunnan Province, China
| | - Xin Ye
- Department of Oncology, The First Affiliated Hospital of Shandong First Medical University and Shandong Provincial Qianfoshan Hospital, Shandong Lung Cancer Institute, Shandong Key Laboratory of Rheumatic Disease and Translational Medicine, Jinan, Shandong Province, China No. 16766, Jingshi Road, Jinan, Shandong Province, China
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Zhang Y, Gao H, He H, Liu J, Xu F, Wu S, Zhou J, Cheng Z. Microwave ablation on ex vivo porcine pancreas: The influence of ablation parameters on ablation results and fat liquefaction. Proc Inst Mech Eng H 2024; 238:814-826. [PMID: 39045922 DOI: 10.1177/09544119241261891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/25/2024]
Abstract
The pancreas is adjacent to critical organs; excessive microwave ablation (MWA) can result in serious complications. The purpose of this paper is to provide the reference data of pancreas MWA for clinicians, analyze the ablation outcomes under different ablation parameters, and determine the critical temperature of pancreatic surface fat liquefaction outflow. Combinations of two power levels (30 W and 55 W), three antenna diameters (1.3 mm, 1.6 mm, and 1.9 mm), and three ablation times (1 min, 1.5 min, and 2 min) were applied to an ex vivo pig pancreas. Temperature measurements were taken at four thermocouple points. The center point is located 5 mm horizontally from the antenna slot, with a temperature measurement point located 5 mm above, below, and to the right of the center point. Main effect analysis and variance analysis were used to quantify the influences of each factor on the ablation outcomes. At 30 W, the antenna diameter contributing the most at 48.5%. At 30 W-1.3 mm-1 min, the spherical index (1.41) is closest to 1. At 55 W, the coagulation zone size was almost only affected by the ablation time, with a contribution rate of 28.7%, the temperature at point C exceeds point B. On the surface of the ex vivo porcine pancreas, the fat outflow temperature was 54ã. Ablation combinations with low power, short duration, and small antenna diameter results in a more nearly spherical coagulation zone. When performing MWA on the pancreas, it is advisable to avoid areas with higher fat content, while keeping the pancreatic surface temperature below 54°C.
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Affiliation(s)
- Yubo Zhang
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing, China
| | - Hongjian Gao
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing, China
| | - Huijing He
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing, China
| | - Ju Liu
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing, China
| | - Fan Xu
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing, China
| | - Shuicai Wu
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing, China
| | - Jie Zhou
- Interventional Ultrasound Department, Chinese PLA General Hospital, Beijing, China
| | - Zhigang Cheng
- Interventional Ultrasound Department, Chinese PLA General Hospital, Beijing, China
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Klimek K, Mader N, Happel C, Sabet A, Grünwald F, Groener D. Heat sink effects in thyroid bipolar radiofrequency ablation: an ex vivo study. Sci Rep 2023; 13:19288. [PMID: 37935715 PMCID: PMC10630443 DOI: 10.1038/s41598-023-45926-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Accepted: 10/25/2023] [Indexed: 11/09/2023] Open
Abstract
The study aimed to investigate heat sink effects in radiofrequency ablation (RFA) under thyroid-specific conditions. In an ex vivo model, bovine thyroid lobes were ablated using bipolar RFA with 2.0 kJ energy input at a power level set to 10 W (n = 35) and 25 W (n = 35). Glass vessels (3.0 mm outer diameter) placed within the ablation zone were used to deliver tissue perfusion at various flow rates (0, 0.25, 0.5, 1, 5, 10, 20 ml/min). Temperature was measured in the proximity of the vessel (Tv) and in the non-perfused contralateral region of the ablation zone (Tc), at equal distances to the ablation electrode (d = 8 mm). Maximum temperature within the perfused zone was significantly lowered with Tv ranging from 54.1 ± 1.5 °C (20 ml/min) to 56.9 ± 1.5 °C (0.25 ml/min), compared to Tc from 63.2 ± 3.5 °C (20 ml/min) to 63.2 ± 2.6 °C (0.25 ml/min) (10 W group). The cross-sectional ablation zone area decreased with increasing flow rates from 184 ± 12 mm2 (0 ml/min) to 141 ± 20 mm2 (20 ml/min) at 10 W, and from 207 ± 22 mm2 (0 ml/min) to 158 ± 31 mm2 (20 ml/min) in the 25 W group. Significant heat sink effects were observed under thyroid-specific conditions even at flow rates ≤ 1 ml/min. In thyroid nodules with prominent vasculature, heat dissipation through perfusion may therefore result in clinically relevant limitations to ablation efficacy.
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Affiliation(s)
- Konrad Klimek
- Department of Nuclear Medicine, University Hospital Frankfurt, Goethe University, Theodor Stern Kai 7, 60590, Frankfurt, Germany
| | - Nicolai Mader
- Department of Nuclear Medicine, University Hospital Frankfurt, Goethe University, Theodor Stern Kai 7, 60590, Frankfurt, Germany
| | - Christian Happel
- Department of Nuclear Medicine, University Hospital Frankfurt, Goethe University, Theodor Stern Kai 7, 60590, Frankfurt, Germany
| | - Amir Sabet
- Department of Nuclear Medicine, University Hospital Frankfurt, Goethe University, Theodor Stern Kai 7, 60590, Frankfurt, Germany
| | - Frank Grünwald
- Department of Nuclear Medicine, University Hospital Frankfurt, Goethe University, Theodor Stern Kai 7, 60590, Frankfurt, Germany
| | - Daniel Groener
- Department of Nuclear Medicine, University Hospital Frankfurt, Goethe University, Theodor Stern Kai 7, 60590, Frankfurt, Germany.
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Laimer G, Bauer M, Scharll Y, Schullian P, Bale R. Multi-Probe RFA vs. Single-Probe MWA in an Ex Vivo Bovine Liver Model: Comparison of Volume and Shape of Coagulation Zones. BIOLOGY 2023; 12:1103. [PMID: 37626989 PMCID: PMC10451889 DOI: 10.3390/biology12081103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 08/04/2023] [Accepted: 08/07/2023] [Indexed: 08/27/2023]
Abstract
OBJECTIVES To compare the volumes and shapes of the coagulation zone (CZ) of a multi-probe RFA system (three RFA electrodes) and a single-probe MWA system from the same vendor in an ex vivo bovine liver model. MATERIAL & METHODS A total of 48 CZs were obtained in bovine liver specimens with three different ablation system configurations (single-probe MWA vs. multi-probe RFA with 20 mm inter-probe distance [confluent CZ] vs. multi-probe RFA with 50 mm inter-probe distance [three individual CZs]) at 4, 6, 8, and 10 min ablation time using a fixed ablation protocol. Ablation diameters were measured and ellipticity indices (EIs) and volumes calculated. Calculations for all systems/configurations were compared. RESULTS Volumes and diameters increased with ablation time for all configurations. At 4 and 6 min ablation time volumes obtained with the RFA 50 mm setup, and at 8 and 10 min with the RFA 20 mm setup were the largest at 26.5 ± 4.1 mL, 38.1 ± 5.8 mL, 46.3 ± 4.9 mL, 48.4 ± 7.3 mL, respectively. The single-probe MWA could not reach the volumes of the RFA setups for any of the ablation times evaluated. EI were very similar and almost round for RFA 20 mm and single-probe MWA, and differed significantly to the more ovoid ones for the RFA 50 mm configuration. CONCLUSIONS The multi-probe RFA system employing three electrodes achieved significantly larger ablation volumes in both configurations (confluent CZ and three individual CZs) per time as compared with a single-probe MWA system in this ex vivo bovine liver model.
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Affiliation(s)
| | | | - Yannick Scharll
- Interventional Oncology-Microinvasive Therapy (SIP), Department of Radiology, Medical University Innsbruck, Anichstr. 35, 6020 Innsbruck, Austria; (G.L.)
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Three-dimensional assessment of vascular cooling effects on hepatic microwave ablation in a standardized ex vivo model. Sci Rep 2022; 12:17061. [PMID: 36224235 PMCID: PMC9556636 DOI: 10.1038/s41598-022-21437-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 09/27/2022] [Indexed: 12/30/2022] Open
Abstract
The aim of this study was a three-dimensional analysis of vascular cooling effects on microwave ablation (MWA) in an ex vivo porcine model. A glass tube, placed in parallel to the microwave antenna at distances of 2.5, 5.0 and 10.0 mm (A-V distance), simulated a natural liver vessel. Seven flow rates (0, 1, 2, 5, 10, 100, 500 ml/min) were evaluated. Ablations were segmented into 2 mm slices for a 3D-reconstruction. A qualitative and quantitative analysis was performed. 126 experiments were carried out. Cooling effects occurred in all test series with flow rates ≥ 2 ml/min in the ablation periphery. These cooling effects had no impact on the total ablation volume (p > 0.05) but led to changes in ablation shape at A-V distances of 5.0 mm and 10.0 mm. Contrary, at a A-V distance of 2.5 mm only flow rates of ≥ 10 ml/min led to relevant cooling effects in the ablation centre. These cooling effects influenced the ablation shape, whereas the total ablation volume was reduced only at a maximal flow rate of 500 ml/min (p = 0.002). Relevant cooling effects exist in MWA. They mainly depend on the distance of the vessel to the ablation centre.
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Microwave versus radiofrequency ablation for the treatment of liver malignancies: a randomized controlled phase 2 trial. Sci Rep 2022; 12:316. [PMID: 35013377 PMCID: PMC8748896 DOI: 10.1038/s41598-021-03802-x] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Accepted: 12/08/2021] [Indexed: 12/24/2022] Open
Abstract
Microwave (MWA) and radiofrequency ablation (RFA) are main ablative techniques for hepatocellular carcinoma (HCC) and colorectal liver metastasis (MT). This randomized phase 2 clinical trial compares the effectiveness of MWA and RFA as well as morphology of corresponding ablation zones. HCC and MT patients with 1.5–4 cm tumors, suitable for ablation, were randomized into MWA or RFA Groups. The primary endpoint was short-to-long diameter ratio of ablation zone (SLR). Primary technical success (TS) and a cumulative local tumor progression (LTP) after a median 2-year follow-up were compared. Between June 2015 and April 2020, 82 patients were randomly assigned (41 patients per group). For the per-protocol analysis, five patients were excluded. MWA created larger ablation zones than RFA (p = 0.036) although without differences in SLR (0.5 for both groups, p = 0.229). The TS was achieved in 98% (46/47) and 90% (45/50) (p = 0.108), and LTP was observed in 21% (10/47) vs. 12% (6/50) (OR 1.9 [95% CI 0.66–5.3], p = 0.238) of tumors in MWA vs. RFA Group, respectively. Major complications were found in 5 cases (11%) vs. 2 cases (4%), without statistical significance. MWA and RFA show similar SLR, effectiveness and safety in liver tumors between 1.5 and 4 cm.
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Thomas MN, Dieplinger G, Datta RR, Kleinert R, Fuchs HF, Bunck A, Peterhans M, Bruns CJ, Stippel D, Wahba R. Navigated laparoscopic microwave ablation of tumour mimics in pig livers: a randomized ex-vivo experimental trial. Surg Endosc 2021; 35:6763-6769. [PMID: 33289054 PMCID: PMC8599321 DOI: 10.1007/s00464-020-08180-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 11/15/2020] [Indexed: 12/13/2022]
Abstract
BACKGROUND In order to efficiently perform laparoscopic microwave ablation of liver tumours precise positioning of the ablation probe is mandatory. This study evaluates the precision and ablation accuracy using the innovative laparoscopic stereotactic navigation system CAS-One-SPOT in comparison to 2d ultrasound guided laparoscopic ablation procedures. METHODS In a pig liver ablation model four surgeons, experienced (n = 2) and inexperienced (n = 2) in laparoscopic ablation procedures, were randomized for 2d ultrasound guided laparoscopic or stereotactic navigated laparoscopic ablation procedures. Each surgeon performed a total of 20 ablations. Total attempts of needle placements, time from tumor localization till beginning of ablation and ablation accuracy were analyzed. RESULTS The use of the laparoscopic stereotactic navigation system led to a significant reduction in total attempts of needle placement. The experienced group of surgeons reduced the mean number of attempts from 2.75 ± 2.291 in the 2d ultrasound guided ablation group to 1.45 ± 1.191 (p = 0.0302) attempts in the stereotactic navigation group. Comparable results could be observed in the inexperienced group with a reduction of 2.5 ± 1.50 to 1.15 ± 0.489 (p = 0.0005). This was accompanied by a significant time saving from 101.3 ± 112.1 s to 48.75 ± 27.76 s (p = 0.0491) in the experienced and 165.5 ± 98.9 s to 66.75 ± 21.96 s (p < 0.0001) in the inexperienced surgeon group. The accuracy of the ablation process was hereby not impaired as postinterventional sectioning of the ablation zone revealed. CONCLUSION The use of a stereotactic navigation system for laparoscopic microwave ablation procedures of liver tumors significantly reduces the attempts and time of predicted correct needle placement for novices and experienced surgeons without impairing the accuracy of the ablation procedure.
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Affiliation(s)
- M N Thomas
- Department of General, Visceral, Cancer and Transplant Surgery, University of Cologne, Faculty of Medicine and University Hospital Cologne, Kerpener Straße 62, 50937, Cologne, Germany.
| | - G Dieplinger
- Department of General, Visceral, Cancer and Transplant Surgery, University of Cologne, Faculty of Medicine and University Hospital Cologne, Kerpener Straße 62, 50937, Cologne, Germany
| | - R R Datta
- Department of General, Visceral, Cancer and Transplant Surgery, University of Cologne, Faculty of Medicine and University Hospital Cologne, Kerpener Straße 62, 50937, Cologne, Germany
| | - R Kleinert
- Department of General, Visceral, Cancer and Transplant Surgery, University of Cologne, Faculty of Medicine and University Hospital Cologne, Kerpener Straße 62, 50937, Cologne, Germany
| | - H F Fuchs
- Department of General, Visceral, Cancer and Transplant Surgery, University of Cologne, Faculty of Medicine and University Hospital Cologne, Kerpener Straße 62, 50937, Cologne, Germany
| | - A Bunck
- Department of Diagnostic and Interventional Radiology, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | | | - C J Bruns
- Department of General, Visceral, Cancer and Transplant Surgery, University of Cologne, Faculty of Medicine and University Hospital Cologne, Kerpener Straße 62, 50937, Cologne, Germany
| | - D Stippel
- Department of General, Visceral, Cancer and Transplant Surgery, University of Cologne, Faculty of Medicine and University Hospital Cologne, Kerpener Straße 62, 50937, Cologne, Germany
| | - R Wahba
- Department of General, Visceral, Cancer and Transplant Surgery, University of Cologne, Faculty of Medicine and University Hospital Cologne, Kerpener Straße 62, 50937, Cologne, Germany
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Poch FGM, Neizert CA, Geyer B, Gemeinhardt O, Niehues SM, Vahldiek JL, Bressem KK, Lehmann KS. Perivascular vital cells in the ablation center after multibipolar radiofrequency ablation in an in vivo porcine model. Sci Rep 2021; 11:13886. [PMID: 34230573 PMCID: PMC8260723 DOI: 10.1038/s41598-021-93406-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Accepted: 06/24/2021] [Indexed: 11/25/2022] Open
Abstract
Multibipolar radiofrequency ablation (RFA) is an advanced ablation technique for early stage hepatocellular carcinoma and liver metastases. Vessel cooling in multibipolar RFA has not been systematically investigated. The objective of this study was to evaluate the presence of perivascular vital cells within the ablation zone after multibipolar RFA. Multibipolar RFA were performed in domestic pigs in vivo. Three internally cooled bipolar RFA applicators were used simultaneously. Three experimental settings were planned: (1) inter-applicator-distance: 15 mm; (2) inter-applicator-distance: 20 mm; (3) inter-applicator-distance: 20 mm with hepatic inflow occlusion (Pringle maneuver). A vitality staining was used to analyze liver cell vitality around all vessels in the ablation center with a diameter > 0.5 mm histologically. 771 vessels were identified. No vital tissue was seen around 423 out of 429 vessels (98.6%) situated within the central white zone. Vital cells could be observed around major hepatic vessels situated adjacent to the ablation center. Vessel diameter (> 3.0 mm; p < 0.05) and low vessel-to-ablation-center distance (< 0.2 mm; p < 0.05) were identified as risk factors for incomplete ablation adjacent to hepatic vessels. The vast majority of vessels, which were localized in the clinically relevant white zone, showed no vital perivascular cells, regardless of vessel diameter and vessel type. However, there was a risk of incomplete ablation around major hepatic vessels situated directly within the ablation center. A Pringle maneuver could avoid incomplete ablations.
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Affiliation(s)
- F G M Poch
- Department of General, Visceral and Vascular Surgery, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Campus Benjamin Franklin, Berlin - Hindenburgdamm 30, 12203, Berlin, Germany.
| | - C A Neizert
- Department of General, Visceral and Vascular Surgery, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Campus Benjamin Franklin, Berlin - Hindenburgdamm 30, 12203, Berlin, Germany
| | - B Geyer
- Department of General, Visceral and Vascular Surgery, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Campus Benjamin Franklin, Berlin - Hindenburgdamm 30, 12203, Berlin, Germany
| | - O Gemeinhardt
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Campus Benjamin Franklin, Berlin - Hindenburgdamm 30, 12203, Berlin, Germany
| | - S M Niehues
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Campus Benjamin Franklin, Berlin - Hindenburgdamm 30, 12203, Berlin, Germany
| | - J L Vahldiek
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Campus Benjamin Franklin, Berlin - Hindenburgdamm 30, 12203, Berlin, Germany
| | - K K Bressem
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Campus Benjamin Franklin, Berlin - Hindenburgdamm 30, 12203, Berlin, Germany
| | - K S Lehmann
- Department of General, Visceral and Vascular Surgery, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Campus Benjamin Franklin, Berlin - Hindenburgdamm 30, 12203, Berlin, Germany
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Liu JF, Shen W, Huang D, Song T, Tao W, Liu Q, Huang YQ, Zhang XM, Xia LJ, Wu DS, Liu H, Chen FY, Liu TH, Peng BG, Liu YQ. Expert consensus of Chinese Association for the Study of Pain on the radiofrequency therapy technology in the Department of Pain. World J Clin Cases 2021; 9:2123-2135. [PMID: 33850931 PMCID: PMC8017496 DOI: 10.12998/wjcc.v9.i9.2123] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 03/05/2021] [Accepted: 03/15/2021] [Indexed: 02/06/2023] Open
Abstract
On the basis of continuous improvement in recent years, radiofrequency therapy technology has been widely developed, and has become an effective method for the treatment of various intractable pain. Radiofrequency therapy is a technique that uses special equipment and puncture needles to output ultra-high frequency radio waves and accurately act on local tissues. In order to standardize the application of radiofrequency technology in the treatment of painful diseases, Chinese Association for the Study of Pain (CASP) has developed a consensus proposed by many domestic experts and scholars.
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Affiliation(s)
- Jin-Feng Liu
- Department of Algology, The Second Affiliated Hospital of Harbin Medical University, Harbin 150086, Heilongjiang Province, China
| | - Wen Shen
- Department of Algology, Affiliated Hospital of Xuzhou Medical University, Xuzhou 221000, Jiangsu Province, China
| | - Dong Huang
- Department of Algology, The Third Xiangya Hospital of Central South University, Changsha 410000, Hunan Province, China
| | - Tao Song
- Department of Algology, The First Affiliated Hospital of China Medical University, Shenyang 110000, Liaoning Province, China
| | - Wei Tao
- Department of Neurosurgery, Shenzhen University General Hospital, Shenzhen 518000, Guangdong Province, China
| | - Qing Liu
- Department of Algology, The Affiliated T.C.M Hospital of Southwest Medical University, Luzhou 646000, Sichuan Province, China
| | - You-Qing Huang
- Department of Algology, The Second Affiliated Hospital of Kunming Medical University, Kunming 650000, Yunnan Province, China
| | - Xiao-Mei Zhang
- Department of Algology, The First Affiliated Hospital of Kunming Medical University, Kunming 650000, Yunnan Province, China
| | - Ling-Jie Xia
- Department of Algology, Henan Provincial Hospital, Zhengzhou 450000, Henan Province, China
| | - Da-Sheng Wu
- Department of Algology, Jilin Province People's Hospital, Changchun 130000, Jilin Province, China
| | - Hui Liu
- Department of Algology, West China Hospital of Sichuan University, Chengdu 610000, Sichuan Province, China
| | - Fu-Yong Chen
- Department of Neurosurgery, Shenzhen University General Hospital, Shenzhen 518000, Guangdong Province, China
| | - Tang-Hua Liu
- Department of Algology, The Third People's Hospital of Yibin, Yibin 644000, Sichuan Province, China
| | - Bao-Gan Peng
- Department of Orthopedics, The Third Medical Center, General Hospital of the Chinese People’s Liberation Army, Beijing 100039, China
| | - Yan-Qing Liu
- Department of Algology, Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China
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Pregel P, Scala E, Bullone M, Martano M, Nozza L, Garberoglio S, Garberoglio R, Bollo E, Scaglione FE. Radiofrequency Thermoablation On Ex Vivo Animal Tissues: Changes on Isolated Swine Thyroids. Front Endocrinol (Lausanne) 2021; 12:575565. [PMID: 34177792 PMCID: PMC8222995 DOI: 10.3389/fendo.2021.575565] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 05/25/2021] [Indexed: 11/17/2022] Open
Abstract
The use of Radiofrequency thermoablation (RFA) for treating large thyroid nodules is limited by the modest efficiency of the available systems in terms of volume of the ablation zones (AZs). This increases the risk of incomplete ablation of the nodule. Systems employing perfused electrodes have been developed to increase the volume of the AZ. Aim of this study is to compare the size of the AZ induced by RFA systems using internally cooled perfused vs. non-perfused electrodes in swine thyroids. RFAs were performed on 40 freshly isolated swine thyroids using both systems. The perfused system was tested using 0.9% saline, 7% and 18% hypertonic saline solutions. Energy delivery to the tissue was stopped when tissue conductivity dropped (real life simulations) and after an established time of 20 seconds (controlled duration). Following RFA, thyroids were transversally and longitudinally cut. Photographs were taken for macroscopic morphometry of the ablated zones before and after formalin fixation, to evaluate tissue shrinkage. Microscopic morphometry was performed on PAS stained sections. In real life simulation experiments, gross morphometry revealed that AZs produced with electrodes perfused using 7.0% saline are larger compared to isotonic saline. Microscopically, all the conditions tested using the perfused system produced larger AZs compared to non-perfused system after 20 seconds of RFA. In conclusion, the perfusion with 7.0% NaCl solution increased the electrical conductivity of the tissue in real life simulations, resulting in larger ablated areas compared to the use of isotonic saline.
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Affiliation(s)
- Paola Pregel
- Dipartimento di Scienze Veterinarie, Università degli Studi di Torino, Torino, Italy
- *Correspondence: Paola Pregel,
| | - Elisa Scala
- Dipartimento di Scienze Veterinarie, Università degli Studi di Torino, Torino, Italy
- Evidensia Specialisthästsjukhuset, Strömsholm, Sweden
| | - Michela Bullone
- Dipartimento di Scienze Veterinarie, Università degli Studi di Torino, Torino, Italy
| | - Marina Martano
- Dipartimento di Scienze Veterinarie, Università degli Studi di Torino, Torino, Italy
- Dipartimento di Scienze Medico-Veterinarie, Università di Parma, Parma, Italy
| | - Linda Nozza
- Dipartimento di Scienze Veterinarie, Università degli Studi di Torino, Torino, Italy
| | - Sara Garberoglio
- Dipartimento di Scienze Mediche, Università degli Studi di Torino, Torino, Italy
| | - Roberto Garberoglio
- Dipartimento di Scienze Mediche, Università degli Studi di Torino, Torino, Italy
| | - Enrico Bollo
- Dipartimento di Scienze Veterinarie, Università degli Studi di Torino, Torino, Italy
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Radiofrequency Ablation by a 21-Gauge Internally Cooled Electrode: Ex Vivo and In Vivo Evaluation by Rat Liver. Cardiovasc Intervent Radiol 2020; 44:150-155. [PMID: 33078230 DOI: 10.1007/s00270-020-02660-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 09/18/2020] [Indexed: 10/23/2022]
Abstract
PURPOSE To evaluate the coagulative performance of a 21-gauge (G) internally cooled radiofrequency (RF) electrode using ex vivo and in vivo rat liver. MATERIALS AND METHODS We developed a prototype of 21-G internally cooled monopolar RF electrode with 5.0 mm active tip length. The ablative zone size created by this electrode was evaluated in ex vivo and in vivo rat liver. Five RF powers (3 W, 5 W, 7 W, 9 W, and 11 W) were applied with and without circulation of chilled water within the electrode. The ablation zone sizes were compared. Histopathological evaluation of the ablation zone was also performed at 24 h and at 7 days after RF ablation. RESULTS From ex vivo experiments, the ablation volume was found to increase significantly when RF energy was applied with the chilled water circulation. Results of in vivo experiments demonstrate that the ablation volume reached its maximum value when RF power of 7 W was applied (532.3 ± 110.3 mm3). Histopathological examination showed delineated coagulation necrosis at 24 h after RF ablation, which clarified the ablation zone border. Fibrotic change was also observed at 7 days after RF ablation. CONCLUSION RF ablation using a 21-gauge electrode produced coagulation necrosis in the rat liver. The ablation volume became maximum when RF power of 7 W was applied with chilled water circulation.
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Influence of interapplicator distance on multibipolar radiofrequency ablation during physiological and interrupted liver perfusion in an in vivo porcine model. Sci Rep 2020; 10:16210. [PMID: 33004845 PMCID: PMC7529885 DOI: 10.1038/s41598-020-71512-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 08/17/2020] [Indexed: 12/12/2022] Open
Abstract
Radiofrequency ablation (RFA) is a curative treatment option for early stage hepatocellular carcinoma (HCC). Vascular inflow occlusion to the liver (Pringle manoeuvre) and multibipolar RFA (mbRFA) represent possibilities to generate large ablations. This study evaluated the impact of different interapplicator distances and a Pringle manoeuvre on ablation area and geometry of mbRFA. 24 mbRFA were planned in porcine livers in vivo. Test series with continuous blood flow had an interapplicator distance of 20 mm and 15 mm, respectively. For a Pringle manoeuvre, interapplicator distance was predefined at 20 mm. After liver dissection, ablation area and geometry were analysed macroscopically and histologically. Confluent and homogenous ablations could be achieved with a Pringle manoeuvre and an interapplicator distance of 15 mm with sustained hepatic blood flow. Ablation geometry was inhomogeneous with an applicator distance of 20 mm with physiological liver perfusion. A Pringle manoeuvre led to a fourfold increase in ablation area in comparison to sustained hepatic blood flow (p < 0.001). Interapplicator distance affects ablation geometry of mbRFA. Strict adherence to the planned applicator distance is advisable under continuous blood flow. The application of a Pringle manoeuvre should be considered when compliance with the interapplicator distance cannot be guaranteed.
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14
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Hui TCH, Brace CL, Hinshaw JL, Quek LHH, Huang IKH, Kwan J, Lim GHT, Lee FT, Pua U. Microwave ablation of the liver in a live porcine model: the impact of power, time and total energy on ablation zone size and shape. Int J Hyperthermia 2020; 37:668-676. [DOI: 10.1080/02656736.2020.1774083] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Affiliation(s)
| | - Christopher Lee Brace
- Department of Radiology and Biomedical Engineering, University of Wisconsin, Madison, WI, USA
| | - J. Louis Hinshaw
- Department of Radiology and Urology, University of Wisconsin, Madison, WI, USA
| | | | | | - Justin Kwan
- Department of Diagnostic Radiology, Tan Tock Seng Hospital, Singapore, Singapore
| | - Gavin Hock Tai Lim
- Department of Diagnostic Radiology, Tan Tock Seng Hospital, Singapore, Singapore
| | - Fred T. Lee
- Department of Diagnostic Radiology, Tan Tock Seng Hospital, Singapore, Singapore
- Department of Radiology and Urology, University of Wisconsin, Madison, WI, USA
| | - Uei Pua
- Department of Diagnostic Radiology, Tan Tock Seng Hospital, Singapore, Singapore
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Vo Chieu VD, Wacker F, Rieder C, Pöhler GH, Schumann C, Ballhausen H, Ringe KI. Ablation zone geometry after CT-guided hepatic microwave ablation: evaluation of a semi-automatic software and comparison of two different ablation systems. Int J Hyperthermia 2020; 37:533-541. [PMID: 32468872 DOI: 10.1080/02656736.2020.1766704] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Purpose: The aims of this study were to evaluate a semi-automatic segmentation software for assessment of ablation zone geometry in computed tomography (CT)-guided microwave ablation (MWA) of liver tumors and to compare two different MWA systems.Material and Methods: 27 patients with 40 hepatic tumors (primary liver tumor n = 20, metastases n = 20) referred for CT-guided MWA were included in this retrospective IRB-approved study. MWA was performed using two systems (system 1: 915 MHz; n = 20; system 2: 2.45 GHz; n = 20). Ablation zone segmentation and ellipticity index calculations were performed using SAFIR (Software Assistant for Interventional Radiology). To validate semi-automatic software calculations, results (2 perpendicular diameters, ellipticity index, volume) were compared with those of manual analysis (intraclass correlation, Pearson's correlation, Mann-Whitney U test; p < 0.05 deemed significant.Results: Manual measurements of mean maximum ablation zone diameters were 43 mm (system 1) and 34 mm (system 2), respectively. Correlations between manual and semi-automatic measurements were r = 0.72 and r = 0.66 (both p < 0.0001) for perpendicular diameters, and r = 0.98 (p < 0.001) for volume. Manual analysis demonstrated that ablation zones created with system 2 had a significantly lower ellipticity index compared to system 1 (mean 1.17 vs. 1.86, p < 0.0001). Results correlated significantly with semi-automatic software measurements (r = 0.71, p < 0.0001).Conclusion: Semi-automatic assessment of ablation zone geometry using SAFIR is feasible. Software-assisted evaluation of ablation zones may prove beneficial with complex ablation procedures, especially for less experienced operators. The 2.45 GHz MWA system generated a significantly more spherical ablation zone compared to the 915 MHz system. The choice of a specific MWA system significantly influences ablation zone geometry.
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Affiliation(s)
- Van Dai Vo Chieu
- Department of Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany
| | - Frank Wacker
- Department of Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany
| | - Christian Rieder
- Fraunhofer Institute for Digital Medicine MEVIS, Bremen, Germany
| | - Gesa H Pöhler
- Department of Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany
| | | | - Hanne Ballhausen
- Fraunhofer Institute for Digital Medicine MEVIS, Bremen, Germany
| | - Kristina I Ringe
- Department of Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany
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Geyer B, Poch FGM, Gemeinhardt O, Neizert CA, Niehues SM, Vahldiek JL, Klopfleisch R, Lehmann KS. Microwave ablation zones are larger than they macroscopically appear - Reevaluation based on NADH vitality staining ex vivo. Clin Hemorheol Microcirc 2019; 73:371-378. [DOI: 10.3233/ch-190583] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Beatrice Geyer
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of General, Visceral and Vascular Surgery – Campus Benjamin Franklin, Berlin, Germany
| | - Franz G. M. Poch
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of General, Visceral and Vascular Surgery – Campus Benjamin Franklin, Berlin, Germany
| | - Ole Gemeinhardt
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Radiology – Campus Mitte, Berlin, Germany
| | - Christina A. Neizert
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of General, Visceral and Vascular Surgery – Campus Benjamin Franklin, Berlin, Germany
| | - Stefan M. Niehues
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Radiology – Campus Benjamin Franklin, Berlin, Germany
| | - Janis L. Vahldiek
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Radiology – Campus Benjamin Franklin, Berlin, Germany
| | - Robert Klopfleisch
- Institute of Veterinary Pathology, Freie Universität Berlin, Berlin, Germany
| | - Kai S. Lehmann
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of General, Visceral and Vascular Surgery – Campus Benjamin Franklin, Berlin, Germany
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17
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Lopresto V, Strigari L, Farina L, Minosse S, Pinto R, D’Alessio D, Cassano B, Cavagnaro M. CT-based investigation of the contraction ofex vivotissue undergoing microwave thermal ablation. ACTA ACUST UNITED AC 2018. [DOI: 10.1088/1361-6560/aaaf07] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Cassinotto C, Denys A, Gay F, Duran R, Hocquelet A, Piron L, Guiu B. Radiofrequency Ablation of Liver Tumors: No Difference in the Ablation Zone Volume Between Cirrhotic and Healthy Liver. Cardiovasc Intervent Radiol 2018; 41:905-911. [PMID: 29484466 DOI: 10.1007/s00270-018-1898-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 02/07/2018] [Indexed: 01/20/2023]
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Poch FGM, Rieder C, Ballhausen H, Knappe V, Ritz JP, Gemeinhardt O, Kreis ME, Lehmann KS. Finding Optimal Ablation Parameters for Multipolar Radiofrequency Ablation. Surg Innov 2017; 24:205-213. [PMID: 28193132 DOI: 10.1177/1553350617692492] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
PURPOSE Radiofrequency ablation (RFA) for primary liver tumors and liver metastases is restricted by a limited ablation size. Multipolar RFA is a technical advancement of RFA, which is able to achieve larger ablations. The aim of this ex vivo study was to determine optimal ablation parameters for multipolar RFA depending on applicator distance and energy input. METHODS RFA was carried out ex vivo in porcine livers with three internally cooled, bipolar applicators in multipolar ablation mode. Three different applicator distances were used and five different energy inputs were examined. Ablation zones were sliced along the cross-sectional area at the largest ablation diameter, orthogonally to the applicators. These slices were digitally measured and analyzed. RESULTS Sixty RFA were carried out. A limited growth of ablation area was seen in all test series. This increase was dependent on ablation time, but not on applicator distance. A steady state between energy input and energy loss was not observed. A saturation of the minimum radius of the ablation zone was reached. Differences in ablation radius between the three test series were seen for lowest and highest energy input ( P < .05). No differences were seen for medium amounts of energy ( P > .05). CONCLUSIONS The ablation parameters applicator distance and energy input can be chosen in such a way, that minor deviations of the preplanned ablation parameters have no influence on the size of the ablation area.
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Affiliation(s)
| | - Christian Rieder
- 2 Fraunhofer MEVIS, Institute for Medical Image Computing, Bremen, Germany
| | - Hanne Ballhausen
- 2 Fraunhofer MEVIS, Institute for Medical Image Computing, Bremen, Germany
| | - Verena Knappe
- 3 Laser- und Medizin-Technologie GmbH, Berlin, Germany
| | - Jörg Peter Ritz
- 4 Klinik für Allgemein- und Viszeralchirurgie, HELIOS Kliniken Schwerin, Schwerin, Germany
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20
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Yoon JH, Lee JM, Woo S, Hwang EJ, Hwang I, Choi W, Han JK, Choi BI. Switching bipolar hepatic radiofrequency ablation using internally cooled wet electrodes: comparison with consecutive monopolar and switching monopolar modes. Br J Radiol 2015; 88:20140468. [PMID: 25873479 DOI: 10.1259/bjr.20140468] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
OBJECTIVE To evaluate whether switching bipolar radiofrequency ablation (SB-RFA) using three internally cooled wet (ICW) electrodes can induce coagulations >5 cm in porcine livers with better efficiency than consecutive monopolar (CM) or switching monopolar (SM) modes. METHODS A total of 60 coagulations were made in 15 in vivo porcine livers using three 17-gauge ICW electrodes and a multichannel radiofrequency (RF) generator. RF energy (approximately 200 W) was applied in CM mode (Group A, n = 20) for 24 min, SM mode for 12 min (Group B, n = 20) or switching bipolar (SB) mode for 12 min (Group C, n = 20) in in vivo porcine livers. Thereafter, the delivered RFA energy, as well as the shape and dimension of coagulations were compared among the groups. RESULTS Spherical- or oval-shaped ablations were created in 30% (6/20), 85% (17/20) and 90% (18/20) of coagulations in the CM, SM and SB groups, respectively (p = 0.003). SB-RFA created ablations >5 cm in minimum diameter (Dmin) in 65% (13/20) of porcine livers, whereas SM- or CM-RFA created ablations >5 cm in only 25% (5/20) and 20% (4/20) of porcine livers, respectively (p = 0.03). The mean Dmin of coagulations was significantly larger in Group C than in Groups A and B (5.1 ± 0.9, 3.9 ± 1.2 and 4.4 ± 1.0 cm, respectively, p = 0.002) at a lower delivered RF energy level (76.8 ± 14.3, 120.9 ± 24.5 and 114.2 ± 18.3 kJ, respectively, p < 0.001). CONCLUSION SB-RFA using three ICW electrodes can create coagulations >5 cm in diameter with better efficiency than do SM- or CM-RFA. ADVANCES IN KNOWLEDGE SB-RFA can create large, regular ablation zones with better time-energy efficiency than do CM- or SM-RFA.
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Affiliation(s)
- J H Yoon
- 1 Department of Radiology, Seoul National University Hospital, Seoul, Republic of Korea
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21
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A comparison of internally water-perfused and cryogenically cooled monopolar and bipolar radiofrequency applicators in ex vivo liver samples. Acad Radiol 2014; 21:661-6. [PMID: 24703480 DOI: 10.1016/j.acra.2014.02.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Revised: 02/04/2014] [Accepted: 02/04/2014] [Indexed: 12/19/2022]
Abstract
RATIONALE AND OBJECTIVES To evaluate the ex vivo ablation zones created in hepatic tissue using monopolar and bipolar gas- and water-cooled radiofrequency (RF) applicators. MATERIALS AND METHODS RF ablations were performed on ex vivo bovine liver tissue using closed circuit water-cooled and closed circuit cryogenically cooled (via CO₂ enthalpy) 15-ga linear-needle applicators. Both monopolar and bipolar electrode applicators were used, with the electric current administered ranging in 50-mA increments from 1100 to 1300 mA for the monopolar case, and from 500 to 700 mA for the bipolar case. Total ablation time was 15 minutes. Six tissue samples were ablated per setting. The ablated volumes were assumed to have a three-dimensional ellipsoid shape, with one long major axis and two smaller minor axes. Gross histology was used to measure the dimensions of the ablated regions to quantify the ablated volume, the dimensions of the axis, and the ratio between the long axis and the smallest minor axis, which was termed the ellipticity index. RESULTS The gas-cooled monopolar applicator achieved the largest short-axis ablation diameter (4.05 ± 0.4 cm), followed by the water-cooled monopolar applicator (3.18 ± 0.29 cm). With the bipolar applicator, the gas-cooled applicators also achieved larger short-axis ablation diameters (3.02 ± 0.15 cm) than the water-cooled applicators (2.72 ± 0.29 cm). The gas-cooled monopolar applicator also provided the largest ablation volume (42.7 ± 10.7 mL) and the most spherically shaped lesions (ellipticity index: 1.21 ± 0.10). Lesion size increased with injected current up to a threshold current of 1200/1250 mA (monopolar water-/gas-cooled) and 600/650 mA (bipolar water-/gas-cooled), but dropped at greater values. CONCLUSIONS Gas-cooled monopolar applicators were superior to the other tested applicators in terms of both volume and sphericity of the ablation zone.
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22
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Vollherbst D, Fritz S, Zelzer S, Wachter MF, Wolf MB, Stampfl U, Gnutzmann D, Bellemann N, Schmitz A, Knapp J, Pereira PL, Kauczor HU, Werner J, Radeleff BA, Sommer CM. Specific CT 3D rendering of the treatment zone after Irreversible Electroporation (IRE) in a pig liver model: the "Chebyshev Center Concept" to define the maximum treatable tumor size. BMC Med Imaging 2014; 14:2. [PMID: 24410997 PMCID: PMC3926307 DOI: 10.1186/1471-2342-14-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Accepted: 12/30/2013] [Indexed: 12/18/2022] Open
Abstract
Background Size and shape of the treatment zone after Irreversible electroporation (IRE) can be difficult to depict due to the use of multiple applicators with complex spatial configuration. Exact geometrical definition of the treatment zone, however, is mandatory for acute treatment control since incomplete tumor coverage results in limited oncological outcome. In this study, the “Chebyshev Center Concept” was introduced for CT 3d rendering to assess size and position of the maximum treatable tumor at a specific safety margin. Methods In seven pig livers, three different IRE protocols were applied to create treatment zones of different size and shape: Protocol 1 (n = 5 IREs), Protocol 2 (n = 5 IREs), and Protocol 3 (n = 5 IREs). Contrast-enhanced CT was used to assess the treatment zones. Technique A consisted of a semi-automated software prototype for CT 3d rendering with the “Chebyshev Center Concept” implemented (the “Chebyshev Center” is the center of the largest inscribed sphere within the treatment zone) with automated definition of parameters for size, shape and position. Technique B consisted of standard CT 3d analysis with manual definition of the same parameters but position. Results For Protocol 1 and 2, short diameter of the treatment zone and diameter of the largest inscribed sphere within the treatment zone were not significantly different between Technique A and B. For Protocol 3, short diameter of the treatment zone and diameter of the largest inscribed sphere within the treatment zone were significantly smaller for Technique A compared with Technique B (41.1 ± 13.1 mm versus 53.8 ± 1.1 mm and 39.0 ± 8.4 mm versus 53.8 ± 1.1 mm; p < 0.05 and p < 0.01). For Protocol 1, 2 and 3, sphericity of the treatment zone was significantly larger for Technique A compared with B. Conclusions Regarding size and shape of the treatment zone after IRE, CT 3d rendering with the “Chebyshev Center Concept” implemented provides significantly different results compared with standard CT 3d analysis. Since the latter overestimates the size of the treatment zone, the “Chebyshev Center Concept” could be used for a more objective acute treatment control.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | - Christof M Sommer
- Department of Diagnostic and Interventional Radiology, University Hospital Heidelberg, Heidelberg, Germany.
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Salas N, Castle SM, Leveillee RJ. Radiofrequency ablation for treatment of renal tumors: technological principles and outcomes. Expert Rev Med Devices 2014; 8:695-707. [DOI: 10.1586/erd.11.51] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Radiofrequency Ablation After Arterial Injection of Miriplatin–Iodized Oil Suspension Into Swine Liver: Ablative Zone Size and Tissue Platinum Concentration. Cardiovasc Intervent Radiol 2013; 37:1047-52. [DOI: 10.1007/s00270-013-0779-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 10/10/2013] [Indexed: 12/16/2022]
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25
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Sommer CM, Sommer SA, Sommer WO, Zelzer S, Wolf MB, Bellemann N, Meinzer HP, Radeleff BA, Stampfl U, Kauczor HU, Pereira PL. Optimisation of the coagulation zone for thermal ablation procedures: a theoretical approach with considerations for practical use. Int J Hyperthermia 2013; 29:620-8. [PMID: 24001114 DOI: 10.3109/02656736.2013.828103] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
PURPOSE This paper outlines a theoretical approach for optimisation of the coagulation zone for thermal ablation procedures and considerations for its practical application. METHODS The theoretical approach is outlined in the Cartesian coordinate system. Considerations for practical application are implemented. The optimised coagulation zone is defined as the bare coverage of tumour mass plus a safety margin. The eccentricity of coagulation centre (ECC) is defined as the distance between the coagulation centre and the tumour centre. The direction of the applicator shaft is determined based on the x-axis direction. The tumour centre and coagulation centre are defined within the x/y-plane. The distance between coagulation margin (applicator tip) and tumour margin is called parallel offset (PAO). RESULTS For spherical coagulation shapes, a linear relationship exists between optimised coagulation diameter and ECC. An exponential relationship exists between optimised coagulation volume and ECC. A complex relationship was found between PAO and determinants of ECC, which are ex and ey. PAO is an extremely important parameter, which allows for determination of the optimal applicator tip position in relation to the tumour margin. It can be calculated in such a manner that the optimised coagulation zone is minimised by neutralising dislocation of the coagulation centre in applicator shaft direction. The latter can be realised by withdrawing or further inserting the applicator shaft. CONCLUSIONS The presented concept can be used to optimise the extent of the coagulation zone for thermal ablation procedures after positioning of the applicator. Its inherent advantage is the simple adjustment of the applicator shaft, which obviates the need for a repuncture.
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Affiliation(s)
- Christof M Sommer
- Department of Diagnostic and Interventional Radiology, University Hospital , Heidelberg , Germany
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Comparison of ablation zones among different tissues using 2450-MHz cooled-shaft microwave antenna: results in ex vivo porcine models. PLoS One 2013; 8:e71873. [PMID: 23951262 PMCID: PMC3741232 DOI: 10.1371/journal.pone.0071873] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Accepted: 07/10/2013] [Indexed: 01/16/2023] Open
Abstract
Background For complete tumor ablation in different tissues, it is necessary to investigate the exact coagulation zone of microwave ablation in different tissues. The aim of this study was to compare the extent of microwave ablation zone in muscle, liver and adipose tissue in ex vivo porcine models and assess the shape of microwave coagulation zone among these tissues. Materials and Methods Microwave ablations were performed in ex vivo porcine muscle, liver and adipose tissue using 2450-MHz cooled-shaft microwave antenna. The content of water, fat and protein in these three tissues was determined. Two power increments (40 and 80 W) and five time increments (1, 3, 5, 7, and 10 minutes) were used in this study. Diameters and shapes of the ablation zones were assessed on gross specimens. Results The average percentages of water, fat and protein in these three tissues were significantly different (P < 0.001), respectively. The long-axis and short-axis diameters among these three tissues at each time-power combination were not significantly different (P > 0.05). The coagulation zones were all elliptical in muscle, liver and adipose tissue. When microwave ablation was performed in the tissue containing both muscle and adipose tissue, the coagulation zone was also elliptical. Regardless of the output power, the ellipticity index (EI) value of 1 minute treatment duration was higher than that of 10 minutes treatment duration (P < 0.05). Furthermore, the EI value did not decrease significantly when the treatment duration was more than 5 minutes (P > 0.05). Conclusion The extent of microwave ablation zones was not significantly different among completely different tissues. Microwave ablations with ≥ 5 minutes time duration can induce coagulation zones with clinical desirable shape. Future clinical studies are still required to determine the role of microwave ablation in different tissues.
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Sommer CM, Bryant M, Kortes N, Stampfl U, Bellemann N, Mokry T, Gockner T, Kauczor HU, Pereira PL, Radeleff BA. Microwave ablation in porcine livers applying 5-minute protocols: influence of deployed energy on extent and shape of coagulation. J Vasc Interv Radiol 2013. [PMID: 23177116 DOI: 10.1016/j.jvir.2012.08.029] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
PURPOSE To evaluate the influence of deployed energy on extent and shape of microwave (MW)-induced coagulation in porcine livers applying 5-minute protocols. MATERIALS AND METHODS MW ablations (n = 25) were performed in ex vivo porcine livers (n = 8). Ablation time was 5 minutes. Five study groups were defined, each with different power output: I, 20 W (n = 5); II, 40 W (n = 5); III, 60 W (n = 5); IV, 80 W (n = 5); and V, 105 W (n = 5). Extent and shape of white coagulation was evaluated macroscopically, including short diameter, volume, front margin, coagulation center (distance between center of short diameter of coagulation and applicator tip), and ellipticity index (short diameter/long diameter). Deployed energy was also analyzed. RESULTS Short diameter and volume were significantly different (P<.001 and P<.001) between the groups: I, 23.0 mm and 11.1 cm(3); II, 12.4 mm and 12.4 cm(3); III, 27.0 mm and 17.6 cm(3); IV, 31.0 mm and 29.2 cm(3); and V, 35.0 mm and 42.3 cm(3). Front margin and coagulation center were also significantly different (P<.05 and P<.001): I, 6.0 mm and 13.0 mm; II, 8.0 mm and 11.0 mm; III, 8.0 mm and 14.0 mm; IV, 8.0 mm and 18.0 mm; and V, 10.0 mm and 19.0 mm. Ellipticity index was not significantly different. Deployed energy was significantly different (P<.001): I, 5.7 kJ; II, 11.0 kJ; III, 15.5 kJ; IV, 21.6 kJ; and V, 26.6 kJ. CONCLUSIONS Extent, but not shape, of MW-induced coagulation depends on the deployed energy. Applying the protocols described in this study, significantly different coagulation volumes can be created with an ablation time of 5 minutes but different power output.
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Affiliation(s)
- Christof Matthias Sommer
- Department of Diagnostic and Interventional Radiology, University Hospital Heidelberg, Im Neuenheimer Feld 110, 69120 Heidelberg, Germany.
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Furse A, Miller BJ, McCann C, Kachura JR, Jewett MA, Sherar MD. Radiofrequency coil for the creation of large ablations: ex vivo and in vivo testing. J Vasc Interv Radiol 2013; 23:1522-8. [PMID: 23101925 DOI: 10.1016/j.jvir.2012.08.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Revised: 07/31/2012] [Accepted: 08/13/2012] [Indexed: 01/12/2023] Open
Abstract
PURPOSE Various radiofrequency (RF) ablation electrode designs have been developed to increase ablation volume. Multiple heating cycles and electrode positions are often required, thereby increasing treatment time. The objective of this study was to evaluate the performance of a high-frequency monopolar induction coil designed to produce large thermal lesions (>3 cm) with a single electrode insertion in a treatment time of less than 10 minutes. MATERIALS AND METHODS A monopolar nitinol interstitial coil operated at 27.12 MHz and 200 W was evaluated. Ex vivo performance was tested in excised bovine liver (n = 22). In vivo testing (n = 10) was conducted in livers of seven Yorkshire pigs. Visual inspection, contrast-enhanced computed tomography (CT), and pathologic evaluation of ablation zones were performed. RESULTS Average ablation volumes in ex vivo and in vivo tests were 60.5 cm(3) ± 14.1 (5.9 × 4.4 × 4.4 cm) and 57.1cm(3) ± 13.8 (6.1 × 4.5 × 4.1cm), with average treatment times of 9.0 minutes ± 3.0 and 8.4 minutes ± 2.7, respectively. Contrast-enhanced CT ablation volume measurements corresponded with findings of gross inspection. Pathologic analysis showed morphologic and enzymatic changes suggestive of tissue death within the ablation zones. CONCLUSIONS The RF ablation coil device successfully produced large, uniform ablation volumes in ex vivo and in vivo settings in treatment times of less than 10 minutes. Ex vivo and in vivo lesion sizes were not significantly different (P = .53), suggesting that the heating efficiency of this higher-frequency coil device may help to minimize the heat-sink effect of perfusion.
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Affiliation(s)
- Alex Furse
- Division of Biophysics and Bioimaging, Ontario Cancer Institute, Princess Margaret Hospital, University Health Network, Toronto, Ontario, Canada.
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Ong SL, Gravante G, Metcalfe MS, Dennison AR. History, ethics, advantages and limitations of experimental models for hepatic ablation. World J Gastroenterol 2013; 19:147-54. [PMID: 23345935 PMCID: PMC3547565 DOI: 10.3748/wjg.v19.i2.147] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Revised: 09/10/2012] [Accepted: 09/19/2012] [Indexed: 02/06/2023] Open
Abstract
Numerous techniques developed in medicine require careful evaluation to determine their indications, limitations and potential side effects prior to their clinical use. At present this generally involves the use of animal models which is undesirable from an ethical standpoint, requires complex and time-consuming authorization, and is very expensive. This process is exemplified in the development of hepatic ablation techniques, starting experiments on explanted livers and progressing to safety and efficacy studies in living animals prior to clinical studies. The two main approaches used are ex vivo isolated non-perfused liver models and in vivo animal models. Ex vivo non perfused models are less expensive, easier to obtain but not suitable to study the heat sink effect or experiments requiring several hours. In vivo animal models closely resemble clinical subjects but often are expensive and have small sample sizes due to ethical guidelines. Isolated perfused ex vivo liver models have been used to study drug toxicity, liver failure, organ transplantation and hepatic ablation and combine advantages of both previous models.
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Mulier S, Jiang Y, Wang C, Jamart J, Marchal G, Michel L, Ni Y. Bipolar radiofrequency ablation with four electrodes: Ex vivo liver experiments and finite element method analysis. Influence of inter-electrode distance on coagulation size and geometry. Int J Hyperthermia 2012; 28:686-97. [DOI: 10.3109/02656736.2012.706729] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Cressman ENK, Shenoi MM, Edelman TL, Geeslin MG, Hennings LJ, Zhang Y, Iaizzo PA, Bischof JC. In vivo comparison of simultaneous versus sequential injection technique for thermochemical ablation in a porcine model. Int J Hyperthermia 2012; 28:105-12. [PMID: 22335224 DOI: 10.3109/02656736.2011.644620] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
PURPOSE To investigate simultaneous and sequential injection thermochemical ablation in a porcine model, and compare them to sham and acid-only ablation. MATERIALS AND METHODS This IACUC-approved study involved 11 pigs in an acute setting. Ultrasound was used to guide placement of a thermocouple probe and coaxial device designed for thermochemical ablation. Solutions of 10 M acetic acid and NaOH were used in the study. Four injections per pig were performed in identical order at a total rate of 4 mL/min: saline sham, simultaneous, sequential, and acid only. Volume and sphericity of zones of coagulation were measured. Fixed specimens were examined by H&E stain. RESULTS Average coagulation volumes were 11.2 mL (simultaneous), 19.0 mL (sequential) and 4.4 mL (acid). The highest temperature, 81.3°C, was obtained with simultaneous injection. Average temperatures were 61.1°C (simultaneous), 47.7°C (sequential) and 39.5°C (acid only). Sphericity coefficients (0.83-0.89) had no statistically significant difference among conditions. CONCLUSIONS Thermochemical ablation produced substantial volumes of coagulated tissues relative to the amounts of reagents injected, considerably greater than acid alone in either technique employed. The largest volumes were obtained with sequential injection, yet this came at a price in one case of cardiac arrest. Simultaneous injection yielded the highest recorded temperatures and may be tolerated as well as or better than acid injection alone. Although this pilot study did not show a clear advantage for either sequential or simultaneous methods, the results indicate that thermochemical ablation is attractive for further investigation with regard to both safety and efficacy.
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Affiliation(s)
- Erik N K Cressman
- Department of Radiology, University of Minnesota Medical Center, Minneapolis, Minnesota 55455, USA.
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Czymek R, Nassrallah J, Gebhard M, Schmidt A, Limmer S, Kleemann M, Bruch HP, Hildebrand P. Intrahepatic radiofrequency ablation versus electrochemical treatment in vivo. Surg Oncol 2012; 21:79-86. [DOI: 10.1016/j.suronc.2010.10.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Revised: 10/11/2010] [Accepted: 10/27/2010] [Indexed: 10/18/2022]
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Ablative zone size created by radiofrequency ablation with and without chemoembolization in small hepatocellular carcinomas. Jpn J Radiol 2012; 30:553-9. [PMID: 22610876 DOI: 10.1007/s11604-012-0087-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2012] [Accepted: 04/27/2012] [Indexed: 12/12/2022]
Abstract
PURPOSE We retrospectively evaluated whether combined use of chemoembolization expands ablative zone sizes created by radiofrequency (RF) ablation in patients with small hepatocellular carcinomas (HCCs). MATERIALS AND METHODS Fifty-seven patients treated with single RF ablation for solitary HCC measuring ≤2 cm were assessed. RF ablation alone was done in nine patients and in 48 patients following chemoembolization, with an interval of 0 days in 6, 1-14 days in 27, 15-28 days in 6, and ≥4 weeks in 9. Ablative zone sizes, disappearance of tumor enhancement, and creation of sufficient ablative margins (>5 mm) were evaluated on contrast-enhanced computed tomography (CT) images. RESULTS Both mean long-axis (4.2-4.7 vs. 3.6 ± 0.4 cm, p < 0.04) and short-axis (3.3-3.8 vs. 2.3 ± 0.5 cm, p < 0.03) diameters were expanded significantly when RF ablation was done until 4 weeks after chemoembolization than with RF ablation alone. Tumor enhancement disappeared in all patients. Frequency of achieving sufficient ablative margins was significantly higher when RF ablation was done until 4 weeks after chemoembolization than with RF ablation alone (74.0-83.3 vs. 22.2 %, p < 0.05). CONCLUSION Ablative zones created by RF ablation with chemoembolization become larger than RF ablation alone, leading to secure ablative margins.
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Intrahepatic radiofrequency ablation versus electrochemical treatment ex vivo. J Surg Res 2012; 174:106-13. [PMID: 21195429 DOI: 10.1016/j.jss.2010.11.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 10/27/2010] [Accepted: 11/03/2010] [Indexed: 01/10/2023]
Abstract
BACKGROUND Radiofrequency ablation (RFA) and electrochemical treatment (ECT) are two methods of local liver tumor ablation. A reproducible perfusion model allowed us to compare these methods when applied in proximity to vascular structures. MATERIAL AND METHODS In a porcine liver perfusion model, we used RFA (group A) and ECT (group B) to perform ablations under ultrasound guidance within 10 mm of a vessel and examined the induced necrosis macroscopically and histologically. RESULTS We created 83 lesions (RFA: 59, ECT: 24) in 27 livers. In group A (mean liver weight: 2046 g), perfusion was macroscopically found to limit necrosis in 52.5% of the procedures. Histology demonstrated the destruction of only 30.4% of the vessel walls within the ablation areas. In group B (mean liver weight: 1885 g), we detected reproducible and sharply demarcated ablation areas both macroscopically and histologically. Necrosis was unaffected by nearby vessels. No viable cells were found perivascularly. Histology showed destruction of the vascular endothelium without any discontinuities. We measured pH values of 0.9 (range: 0.6-1.8) at the anode and 12.2 (range: 11.4-12.6) at the cathode. Treatment time was 100 min when a charge of 300 coulombs was delivered. CONCLUSIONS Electrochemical treatment is a method of ablation that creates reproducible and predictable volumes of necrosis. It produces sharply demarcated areas of complete necrosis also in perivascular sites. ECT, however, requires much longer treatment times than RFA. In our model, the effects of RFA were considerably limited by perfusion, which caused incomplete areas of necrosis in proximity to vessels.
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Cressman ENK, Geeslin MG, Shenoi MM, Hennings LJ, Zhang Y, Iaizzo PA, Bischof JC. Concentration and volume effects in thermochemical ablation in vivo: Results in a porcine model. Int J Hyperthermia 2012; 28:113-21. [DOI: 10.3109/02656736.2011.644621] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
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Multipolar radiofrequency ablation using 4-6 applicators simultaneously: a study in the ex vivo bovine liver. Eur J Radiol 2012; 81:2568-75. [PMID: 22297178 DOI: 10.1016/j.ejrad.2011.10.031] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2009] [Accepted: 10/21/2011] [Indexed: 02/03/2023]
Abstract
In this study the volume and shape of coagulation zones after multipolar radiofrequency ablation (RFA) with simultaneous use of 4-6 applicators in the ex vivo bovine liver were investigated. The RF-applicators were positioned in 13 different configurations to simulate ablation of large solitary tumors and simultaneous ablation of multiple lesions with 120 kJ of applied energy/session. In total, 110 coagulation zones were induced. Standardized measurements of the volume and shape of the coagulation zones were carried out on magnetic resonance images and statistically analyzed. The coagulation zones induced with solitary applicators and with 2 applicators were imperceptibly small and incomplete, respectively. At 20mm applicator distance, the total ablated volume was significantly larger if all applicators were arranged in a single group compared to placement in 2 distant applicator groups, each consisting of 3 applicators (p=.001). The mean total coagulated volume ranged from immeasurably small (if 6 solitary applicators were applied simultaneously) to 74.7 cc (if 6 applicators at 30 mm distance between neighboring applicators were combined to a single group). Applicator distance, number and positioning array impacted time and shape. The coagulation zones surrounding groups with 4-6 applicators were regularly shaped, homogeneous and completely fused, and the axial diameters were almost constant. In conclusion, multipolar RFA with 4-6 applicators is feasible. The multipolar simultaneous mode should be applied for large and solitary lesions only, small and multiple tumors should be ablated consecutively in standard multipolar mode with up to 3 applicators.
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The effects of radiofrequency ablation on the hepatic parenchyma: Histological bases for tumor recurrences. Surg Oncol 2011; 20:237-45. [DOI: 10.1016/j.suronc.2010.01.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2009] [Revised: 01/26/2010] [Accepted: 01/27/2010] [Indexed: 01/22/2023]
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Rieder C, Kröger T, Schumann C, Hahn HK. GPU-based real-time approximation of the ablation zone for radiofrequency ablation. IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS 2011; 17:1812-1821. [PMID: 22034298 DOI: 10.1109/tvcg.2011.207] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Percutaneous radiofrequency ablation (RFA) is becoming a standard minimally invasive clinical procedure for the treatment of liver tumors. However, planning the applicator placement such that the malignant tissue is completely destroyed, is a demanding task that requires considerable experience. In this work, we present a fast GPU-based real-time approximation of the ablation zone incorporating the cooling effect of liver vessels. Weighted distance fields of varying RF applicator types are derived from complex numerical simulations to allow a fast estimation of the ablation zone. Furthermore, the heat-sink effect of the cooling blood flow close to the applicator's electrode is estimated by means of a preprocessed thermal equilibrium representation of the liver parenchyma and blood vessels. Utilizing the graphics card, the weighted distance field incorporating the cooling blood flow is calculated using a modular shader framework, which facilitates the real-time visualization of the ablation zone in projected slice views and in volume rendering. The proposed methods are integrated in our software assistant prototype for planning RFA therapy. The software allows the physician to interactively place virtual RF applicator models. The real-time visualization of the corresponding approximated ablation zone facilitates interactive evaluation of the tumor coverage in order to optimize the applicator's placement such that all cancer cells are destroyed by the ablation.
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Neuhaus J, Blachut L, Rabenalt R, Stein T, König F, Wehner M, Liatsikos E, Stolzenburg JU. Efficiency Analysis of Bipolar and Multipolar Radiofrequency Ablation in an In Vivo Porcine Kidney Model Using Three-Dimensional Reconstruction of Histologic Section Series. J Endourol 2011; 25:859-67. [DOI: 10.1089/end.2010.0578] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Affiliation(s)
- Jochen Neuhaus
- Department of Urology, University of Leipzig, Leipzig, Germany
| | - Lisa Blachut
- Department of Urology, University of Leipzig, Leipzig, Germany
| | - Robert Rabenalt
- Department of Urology, University of Duesseldorf, Duesseldorf, Germany
| | | | - Fritjoff König
- Department of Anaesthesiology and Intensive Care Medicine, University of Leipzig, Leipzig, Germany
| | - Markus Wehner
- Department of Anaesthesiology and Intensive Care Medicine, University of Leipzig, Leipzig, Germany
| | - Evangelos Liatsikos
- Department of Urology, University of Leipzig, Leipzig, Germany
- Department of Urology, University of Patras, Patras, Greece
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Radiofrequency ablation versus resection for liver tumours: an evidence-based approach to retrospective comparative studies. J Gastrointest Surg 2011; 15:378-87. [PMID: 21061179 DOI: 10.1007/s11605-010-1377-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2010] [Accepted: 10/19/2010] [Indexed: 02/08/2023]
Abstract
BACKGROUND Recently randomized controlled trials have been advocated to compare radiofrequency ablation (RFA) and hepatic resection (HR) in resectable tumours and determine whether differences in observed survivals result from the heterogeneity in previous studies between RFA (treating unresectable lesions) and HR (treating lesions deemed resectable). We reviewed the literature that directly compares the treatments and employed an evidence-based approach to examine the data. MATERIALS AND METHODS All studies comparing RFA and HR were included. Primary outcomes were the overall survival (OS) and disease-free survival (DFS) at 3 and 5 years. A subgroup analysis was conducted for solitary or small tumors (<4 cm for colorectal metastases (CRM) or <5 cm for hepatocellular carcinoma (HCC)). RESULTS Most studies were retrospective. For CRM, HR was markedly superior to RFA in respect of 3- and 5-year OS as well as 5-year DFS including tumours smaller than 4 cm and solitary lesions. For HCC, HR was markedly superior to RFA for 3- and 5-year OS as well as 3-year DFS, and produced a better OS at 3 years for solitary lesions and DFS at 3 years for small tumours. CONCLUSIONS Multiple factors determine outcomes following treatment of liver tumours. Small or solitary lesions seem the most appropriate ones to study as this reduces the number of confounding variables, but even in these cases HR confers a better OS and DFS than RFA for both CRM and HCC. If our data are confirmed it will be important to examine other factors influencing the response.
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Sustained Growth of the Ex Vivo Ablation Zones’ Critical Short Axis Using Gas-cooled Radiofrequency Applicators. Cardiovasc Intervent Radiol 2010; 34:149-55. [DOI: 10.1007/s00270-010-9946-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2010] [Accepted: 06/28/2010] [Indexed: 01/20/2023]
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Increased ablation zones using a cryo-based internally cooled bipolar RF applicator in ex vivo bovine liver. Invest Radiol 2010; 44:763-8. [PMID: 19838120 DOI: 10.1097/rli.0b013e3181b66d11] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE To evaluate the feasibility of ex vivo ablation implementing a cryo-based internally cooled bipolar radiofrequency (RF) applicator and to determine the influence of power and gas pressure on the size and shape of the resulting ablation zones. MATERIALS AND METHODS Two hundred twenty-five ablations were performed using a custom-built internally CO2-cooled bipolar cryo RF applicator in ex vivo bovine livers. The active tip of the applicator was 55 mm long. RF power (32-50 watts) and gas pressure of cooling medium (500-600 psi) were varied independently. Power was applied in continuous mode. Control group experiments were carried out solely using the RF function at 32, 40, and 50 watts. Ablation duration was 15 minutes for all applications. Experiments were repeated 5 times for all parameter combinations. Short and long axes of the induced white ablation zone were macroscopically assessed. The ablation zone was referred to as homogeneous if complete ablation was observed without spots of untreated tissue. The short axis diameters for the simultaneous application of cryo and RF function were analyzed using a multiple linear regression analysis. An unpaired Mann-Whitney U test was used to analyze the differences between the short axes with RF alone and RF using cryo cooling. RESULTS All ablation zones were homogeneous. Using simultaneous RF ablation function and gas cooling with a single applicator, the long axes of the ablation zones ranged between 42 +/- 2 mm (mean +/- SD) and 59 +/- 5 mm, the short axes between 24 +/- 1 and 44 +/- 1 mm, depending on the parameter combination. At a stable gas pressure level, short axes increased with rising power levels and decreased after reaching a maximum. The maxima of the short axis increased with higher gas pressure levels and were shifted to higher power values. Optimal parameter settings were 46 to 50 watts and 600 psi gas pressure, resulting in a short axis of 44 +/- 1 mm. Short axis weakly correlated with gas pressure (r2 = 0.10) and power (r2 = 0.34) alone, whereas the correlation was r2 = 0.76 for the combined factors. Without cooling, short axis diameters were significantly shorter (P < 0.05), ranging between 13 +/- 2 mm at 50 watts and 15 +/- 2 mm at 32 watts. CONCLUSION The results of this initial ex vivo study show that the combined cryo RF ablation device allows for large ablation volumes using a single needle, which is superior to RF ablation alone.
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Gravante G. Thermal ablation for unresectable liver tumours, time to move forward? World J Gastrointest Surg 2010; 2:1-5. [PMID: 21160826 PMCID: PMC2999191 DOI: 10.4240/wjgs.v2.i1.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 12/09/2009] [Accepted: 12/16/2009] [Indexed: 02/06/2023] Open
Abstract
Even with the advent of laparoscopic techniques for liver tumours, classic resections still represent a major undertaking for numerous liver lesions. The avoidance of surgery using ablative techniques has been the aim for over 20 years. Large volumes can now be rapidly treated with low morbidity with the many technical developments and modifications of the delivery probes. Despite these advances recurrences rates remain high with all of the presently available techniques. The biological and pathophysiological basis underlying may help explain their limitations and are important in understanding where they may be appropriately applied and ways in which they may be improved in the future.
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Affiliation(s)
- Gianpiero Gravante
- Gianpiero Gravante, Department of Hepatobiliary and Pancreatic Surgery, Leicester General Hospital, Gwendolen Road, Leicester LE5 4PW, United Kingdom
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Gravante G, Ong SL, Metcalfe MS, Bhardwaj N, Maddern GJ, Lloyd DM, Dennison AR. Experimental application of electrolysis in the treatment of liver and pancreatic tumours: principles, preclinical and clinical observations and future perspectives. Surg Oncol 2010; 20:106-20. [PMID: 20045634 DOI: 10.1016/j.suronc.2009.12.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2009] [Revised: 11/18/2009] [Accepted: 12/07/2009] [Indexed: 12/12/2022]
Abstract
BACKGROUND Electrolytic ablation (EA) is a treatment that destroys tissues through electrochemical changes in the local microenvironment. This review examined studies using EA for the treatment of liver and pancreatic tumours, in order to define the characteristics that could endow the technique with specific advantages compared with other ablative modalities. METHODS Literature search of all studies focusing on liver and pancreas EA. RESULTS A specific advantage of EA is its safety even when conducted close to major vessels, while a disadvantage is the longer ablation times compared to more frequently employed techniques. Bimodal electric tissue ablation modality combines radiofrequency with EA and produced significant larger ablation zones compared to EA or radiofrequency alone, reducing the time required for ablation. Pancreatic EA has been investigated in experimental studies that confirmed similar advantages to those found with liver ablation, but has never been evaluated on patients. Furthermore, few clinical studies examined the results of liver EA in the short-term but there is no appropriate follow-up to confirm any survival advantage. CONCLUSIONS EA is a safe technique with the potential to treat lesions close to major vessels. Specific clinical studies are required to confirm the technique's safety and eventually demonstrate a survival advantage.
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Affiliation(s)
- G Gravante
- Department of Hepatobiliary and Pancreatic Surgery, University Hospitals of Leicester, Leicester, UK.
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Large-volume multi-tined expandable RF ablation in pig livers: comparison of 2D and volumetric measurements of the ablation zone. Eur Radiol 2009; 20:1073-8. [PMID: 19915850 DOI: 10.1007/s00330-009-1639-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2009] [Revised: 08/28/2009] [Accepted: 09/05/2009] [Indexed: 01/20/2023]
Abstract
OBJECTIVES To compare two-dimensional (2D) and three-dimensional (3D) computed tomography (CT) measurements of ablation zones (AZs) related to the shaft of two different large-volume monopolar multi-tined expandable electrodes. METHODS Percutaneous radiofrequency (RF) ablation was performed in 12 pigs (81.6 +/- 7.8 kg) using two electrodes (LeVeen 5 cm, Rita XL 5 cm; n = 6 in each group). Contrast-enhanced CT with the electrode shaft in place evaluated the AZ. The largest sphere centred on the electrode shaft within the AZ was calculated (1) based on the 2D axial CT image in the plane of the shaft assuming rotational symmetry of the AZ and (2) using prototype software and the 3D volume data of the AZ measured with CT. RESULTS The mean largest diameter of a sphere centred on the electrode shaft was always smaller using the 3D data of the AZ than using 2D CT measurements assuming rotational symmetry of the AZ (3D vs 2D): LeVeen 18.2 +/- 4.8 mm; 24.5 +/- 3.1 mm; p = 0.001; Rita XL 20.0 +/- 3.7 mm; 28.8 +/- 4.9 mm; p = 0.0002. All AZ showed indentations around the tines. CONCLUSIONS Two-dimensional CT measurements assuming rotational symmetry of the AZ overestimate the largest ablated sphere centred on the electrode shaft compared with 3D CT measurements.
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Wahba R, Bangard C, Kleinert R, Rösgen S, Fischer JH, Lackner KJ, Hölscher AH, Stippel DL. Electro-physiological parameters of hepatic radiofrequency ablation—a comparison of an in vitro versus an in vivo porcine liver model. Langenbecks Arch Surg 2009; 394:503-9. [DOI: 10.1007/s00423-009-0475-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2009] [Accepted: 02/20/2009] [Indexed: 10/21/2022]
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Bartolotta TV, Taibbi A, Midiri M, De Maria M. Hepatocellular cancer response to radiofrequency tumor ablation: contrast-enhanced ultrasound. ACTA ACUST UNITED AC 2008; 33:501-11. [PMID: 17786507 DOI: 10.1007/s00261-007-9294-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Radiofrequency ablation (RFA) is increasingly being used as percutaneous treatment of choice for patients with early stage hepatocellular carcinoma (HCC). An accurate assessment of the RFA therapeutic response is of crucial importance, considering that a complete tumor ablation significantly increases patient survival, whereas residual unablated tumor calls for additional treatment. Imaging modalities play a pivotal role in accomplishing this task, but ultrasound (US) is not considered a reliable modality for the evaluation of the real extent of necrosis, even when color/power Doppler techniques are used. Recently, newer microbubble-based US contrast agents used in combination with grey-scale US techniques, which are very sensitive to non-linear behavior of microbubbles, have been introduced. These features have opened new prospects in liver ultrasound and may have a great impact on daily practice, including cost-effective assessment of therapeutic response of percutaneous ablative therapies. Technical evolution of CEUS focusing on findings after RFA are illustrated. These latter are detailed, cross-referenced with the literature and discussed on the basis of our personal experience. Timing of CEUS posttreatment assessment among with advantages and limitations of CEUS are also described with a perspective on further technologic refinement.
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Oshima F, Yamakado K, Nakatsuka A, Takaki H, Makita M, Takeda K. Simultaneous microwave ablation using multiple antennas in explanted bovine livers: relationship between ablative zone and antenna. ACTA ACUST UNITED AC 2008; 26:408-14. [PMID: 18769998 DOI: 10.1007/s11604-008-0251-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Accepted: 04/11/2008] [Indexed: 12/19/2022]
Abstract
PURPOSE Our purpose was to determine the optimal antenna spacing to achieve large ablative zones without indentations when microwave ablation is performed with simultaneous activation of two or three antennas. MATERIALS AND METHODS Microwave ablation was performed with single-antenna activation and simultaneous activation of two or three antennas with a spacing of 1.5, 2.0, 2.5, or 3.0 cm in explanted bovine livers. Microwave energy was applied for 10 min with a power of 45 W. The shapes and sizes of the ablative zones created were recorded and compared. RESULTS The shape of the ablative zone was ellipsoid in the axial plane (along the antenna axis) and spherical in the transverse plane (perpendicular to the antenna axis) in single-antenna ablation. The ablative zones were spherical or ellipsoid in both the axial and transverse planes in two-and three-antenna ablation with an antenna spacing of 2.0 cm or less. Indentations were observed between the ablative zones created by the antennas when the spacing was 2.5 cm or more, reducing the minimum transverse diameter. When two-or three-antenna ablation was performed with a spacing of 2.0 cm or less, the axial and minimum transverse diameters were significantly larger than in single-antenna ablation. The largest volume (almost two or three times the single-activation volume) was achieved in two-or three-antenna ablation with an antenna spacing of 2.0 cm. CONCLUSION We found that simultaneous microwave ablation using multiple microwave antennas creates large ablative zones without indentations when multiple antennas are activated with an antenna spacing of 2.0 cm or less.
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Affiliation(s)
- Fumiyoshi Oshima
- Department of Radiology, Mie University School of Medicine, 2-174 Edobashi, Tsu, 514-8507, Japan
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Mulier S, Ruers T, Michel L, Jamart J, Marchal G, Ni Y. A Place for Radiofrequency Ablation in the Treatment of Resectable Colorectal Liver Metastases? Ann Surg Oncol 2008. [DOI: 10.1245/s10434-008-9951-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Stippel DL, Bangard C, Prenzel K, Yavuzyasar S, Fischer JH, Hölscher AH. Which parameters are needed for targeting a multitined radiofrequency device--an approach to a simple algorithm. Langenbecks Arch Surg 2008; 394:671-9. [PMID: 18288484 DOI: 10.1007/s00423-008-0306-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2007] [Accepted: 01/31/2008] [Indexed: 10/22/2022]
Abstract
BACKGROUND The use of radiofrequency ablation (RFA) for treatment of liver malignancies is limited by the high rate of local recurrences. The aim of this experimental study was to evaluate parameters describing the reproducible target volume of a RFA procedure in order to facilitate better applicator placement. MATERIALS AND METHODS RFA was performed in perfused and nonperfused pig livers. The following parameters were measured: axial and transverse diameter, front margin, coagulation center, diameter of sphere ablated (D(S)), distance to center (DC), and volume. Graphic overlays were utilized to visualize variability. Parameters were evaluated for Rita XL (2 algorithms), LeVeen, and Rita Xli applicators. RESULTS The best prediction of a reproducibly ablated target volume can be made by the diameter of the sphere ablated and the distance of the applicator tip to center of the sphere (DC). The spheres were significantly different in diameter (D(S)) depending on the applicator Rita XL 29 +/- 6 mm, Rita XL(wet) 35 +/- 5 mm, LeVeen 35 +/- 8 mm, Rita Xli 44 +/- 5 mm (perfused livers, p < 0.001). Graphic overlay demonstrated differences in variability that can influence the reliability of the system. CONCLUSIONS D(S) and DC as specific values for each applicator and algorithm facilitate a placement of the applicator relative to the target volume that maximizes the chance of complete ablation.
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Affiliation(s)
- Dirk L Stippel
- Department of Visceral and Vascular Surgery, University of Cologne, Joseph-Stelzmann-Strasse 9, 50931, Cologne, Germany.
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