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Unidirectional ablation minimizes unwanted thermal damage and promotes better thermal ablation efficacy in time-based switching bipolar radiofrequency ablation. Comput Biol Med 2021; 137:104832. [PMID: 34508975 DOI: 10.1016/j.compbiomed.2021.104832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Revised: 09/02/2021] [Accepted: 09/02/2021] [Indexed: 11/22/2022]
Abstract
Switching bipolar radiofrequency ablation (bRFA) is a thermal treatment modality used for liver cancer treatment that is capable of producing larger, more confluent and more regular thermal coagulation. When implemented in the no-touch mode, switching bRFA can prevent tumour track seeding; a medical phenomenon defined by the deposition of cancer cells along the insertion track. Nevertheless, the no-touch mode was found to yield significant unwanted thermal damage as a result of the electrodes' position outside the tumour. It is postulated that the unwanted thermal damage can be minimized if ablation can be directed such that it focuses only within the tumour domain. As it turns out, this can be achieved by partially insulating the active tip of the RF electrodes such that electric current flows in and out of the tissue only through the non-insulated section of the electrode. This concept is known as unidirectional ablation and has been shown to produce the desired effect in monopolar RFA. In this paper, computational models based on a well-established mathematical framework for modelling RFA was developed to investigate if unidirectional ablation can minimize unwanted thermal damage during time-based switching bRFA. From the numerical results, unidirectional ablation was shown to produce treatment efficacy of nearly 100%, while at the same time, minimizing the amount of unwanted thermal damage. Nevertheless, this effect was observed only when the switch interval of the time-based protocol was set to 50 s. An extended switch interval negated the benefits of unidirectional ablation.
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2
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Comparisons between impedance-based and time-based switching bipolar radiofrequency ablation for the treatment of liver cancer. Comput Biol Med 2021; 134:104488. [PMID: 34020132 DOI: 10.1016/j.compbiomed.2021.104488] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 05/06/2021] [Accepted: 05/07/2021] [Indexed: 01/19/2023]
Abstract
Switching bipolar radiofrequency ablation (bRFA) is a cancer treatment technique that activates multiple pairs of electrodes alternately based on a predefined criterion. Various criteria can be used to trigger the switch, such as time (ablation duration) and tissue impedance. In a recent study on time-based switching bRFA, it was determined that a shorter switch interval could produce better treatment outcome than when a longer switch interval was used, which reduces tissue charring and roll-off induced cooling. In this study, it was hypothesized that a more efficacious bRFA treatment can be attained by employing impedance-based switching. This is because ablation per pair can be maximized since there will be no interruption to RF energy delivery until roll-off occurs. This was investigated using a two-compartment 3D computational model. Results showed that impedance-based switching bRFA outperformed time-based switching when the switch interval of the latter is 100 s or higher. When compared to the time-based switching with switch interval of 50 s, the impedance-based model is inferior. It remains to be investigated whether the impedance-based protocol is better than the time-based protocol for a switch interval of 50 s due to the inverse relationship between ablation and treatment efficacies. It was suggested that the choice of impedance-based or time-based switching could ultimately be patient-dependent.
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Yap S, Ooi EH, Foo JJ, Ooi ET. Bipolar radiofrequency ablation treatment of liver cancer employing monopolar needles: A comprehensive investigation on the efficacy of time-based switching. Comput Biol Med 2021; 131:104273. [PMID: 33631495 DOI: 10.1016/j.compbiomed.2021.104273] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 02/09/2021] [Accepted: 02/10/2021] [Indexed: 12/16/2022]
Abstract
Radiofrequency ablation (RFA) is a thermal ablative treatment method that is commonly used to treat liver cancer. However, the thermal coagulation zone generated using the conventional RFA system can only successfully treat tumours up to 3 cm in diameter. Switching bipolar RFA has been proposed as a way to increase the thermal coagulation zone. Presently, the understanding of the underlying thermal processes that takes place during switching bipolar RFA remains limited. Hence, the objective of this study is to provide a comprehensive understanding on the thermal ablative effects of time-based switching bipolar RFA on liver tissue. Five switch intervals, namely 50, 100, 150, 200 and 300 s were investigated using a two-compartment 3D finite element model. The study was performed using two pairs of RF electrodes in a four-probe configuration, where the electrodes were alternated based on their respective switch interval. The physics employed in the present study were verified against experimental data from the literature. Results obtained show that using a shorter switch interval can improve the homogeneity of temperature distribution within the tissue and increase the rate of temperature rise by delaying the occurrence of roll-off. The coagulation volume obtained was the largest using switch interval of 50 s, followed by 100, 150, 200 and 300 s. The present study demonstrated that the transient thermal response of switching bipolar RFA can be improved by using shorter switch intervals.
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Affiliation(s)
- Shelley Yap
- School of Engineering, Monash University Malaysia, Jalan Lagoon Selatan, 47500 Bandar Sunway, Selangor, Malaysia
| | - Ean H Ooi
- School of Engineering, Monash University Malaysia, Jalan Lagoon Selatan, 47500 Bandar Sunway, Selangor, Malaysia; Advanced Engineering Platform, Monash University Malaysia, Jalan Lagoon Selatan, 47500 Bandar Sunway, Selangor, Malaysia.
| | - Ji J Foo
- School of Engineering, Monash University Malaysia, Jalan Lagoon Selatan, 47500 Bandar Sunway, Selangor, Malaysia
| | - Ean T Ooi
- School of Engineering and Information Technology, Faculty of Science and Technology, Federation University, VIC, 3350, Australia
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Radiofrequency ablation with four electrodes as a building block for matrix radiofrequency ablation: Ex vivo liver experiments and finite element method modelling. Influence of electric and activation mode on coagulation size and geometry. Surg Oncol 2020; 33:145-157. [PMID: 32561081 DOI: 10.1016/j.suronc.2020.02.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Accepted: 02/07/2020] [Indexed: 02/06/2023]
Abstract
PURPOSE Radiofrequency ablation (RFA) is increasingly being used to treat unresectable liver tumors. Complete ablation of the tumor and a safety margin is necessary to prevent local recurrence. With current electrodes, size and shape of the ablation zone are highly variable leading to unsatisfactory local recurrence rates, especially for tumors >3 cm. In order to improve predictability, we recently developed a system with four simple electrodes with complete ablation in between the electrodes. This rather small but reliable ablation zone is considered as a building block for matrix radiofrequency ablation (MRFA). In the current study we explored the influence of the electric mode (monopolar or bipolar) and the activation mode (consecutive, simultaneous or switching) on the size and geometry of the ablation zone. MATERIALS AND METHODS The four electrode system was applied in ex vivo bovine liver. The electric and the activation mode were changed one by one, using constant power of 50 W in all experiments. Size and geometry of the ablation zone were measured. Finite element method (FEM) modelling of the experiment was performed. RESULTS In ex vivo liver, a complete and predictable coagulation zone of a 3 × 2 × 2 cm block was obtained most efficiently in the bipolar simultaneous mode due to the combination of the higher heating efficacy of the bipolar mode and the lower impedance by the simultaneous activation of four electrodes, as supported by the FEM simulation. CONCLUSIONS In ex vivo liver, the four electrode system used in a bipolar simultaneous mode offers the best perspectives as building block for MRFA. These results should be confirmed by in vivo experiments.
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A computational theoretical model for radiofrequency ablation of tumor with complex vascularization. Comput Biol Med 2017; 89:282-292. [DOI: 10.1016/j.compbiomed.2017.08.025] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 08/02/2017] [Accepted: 08/22/2017] [Indexed: 02/06/2023]
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Jiang Y, Possebon R, Mulier S, Wang C, Chen F, Feng Y, Xia Q, Liu Y, Yin T, Oyen R, Ni Y. A methodology for constraining power in finite element modeling of radiofrequency ablation. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2017; 33:e2834. [PMID: 27654010 DOI: 10.1002/cnm.2834] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 09/18/2016] [Indexed: 06/06/2023]
Abstract
Radiofrequency ablation (RFA) is a minimally invasive thermal therapy for the treatment of cancer, hyperopia, and cardiac tachyarrhythmia. In RFA, the power delivered to the tissue is a key parameter. The objective of this study was to establish a methodology for the finite element modeling of RFA with constant power. Because of changes in the electric conductivity of tissue with temperature, a nonconventional boundary value problem arises in the mathematic modeling of RFA: neither the voltage (Dirichlet condition) nor the current (Neumann condition), but the power, that is, the product of voltage and current was prescribed on part of boundary. We solved the problem using Lagrange multiplier: the product of the voltage and current on the electrode surface is constrained to be equal to the Joule heating. We theoretically proved the equality between the product of the voltage and current on the surface of the electrode and the Joule heating in the domain. We also proved the well-posedness of the problem of solving the Laplace equation for the electric potential under a constant power constraint prescribed on the electrode surface. The Pennes bioheat transfer equation and the Laplace equation for electric potential augmented with the constraint of constant power were solved simultaneously using the Newton-Raphson algorithm. Three problems for validation were solved. Numerical results were compared either with an analytical solution deduced in this study or with results obtained by ANSYS or experiments. This work provides the finite element modeling of constant power RFA with a firm mathematical basis and opens pathway for achieving the optimal RFA power.
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Affiliation(s)
- Yansheng Jiang
- Department of Radiology, Gasthuisberg University Hospital, Herestraat 49, Leuven, 3000, Belgium
| | - Ricardo Possebon
- Applied Mechanics Group, Graduate Program in Engineering, Federal University of Pampa, Av. Tiarajú 810, Ibirapuitã, CEP 97546-550, Alegrete, Rio Grande do Sul, Brazil
| | - Stefaan Mulier
- Department of Radiology, Gasthuisberg University Hospital, Herestraat 49, Leuven, 3000, Belgium
- Department of Surgery, Leopold Park Clinic, CHIREC Cancer Institute, Froissartstraat 38, Brussels, 1040, Belgium
| | - Chong Wang
- Applied Mechanics Group, Graduate Program in Engineering, Federal University of Pampa, Av. Tiarajú 810, Ibirapuitã, CEP 97546-550, Alegrete, Rio Grande do Sul, Brazil
| | - Feng Chen
- University of Zhe Jiang, Hang Zhou, China
| | - Yuanbo Feng
- Department of Radiology, Gasthuisberg University Hospital, Herestraat 49, Leuven, 3000, Belgium
| | | | - Yewei Liu
- Department of Radiology, Gasthuisberg University Hospital, Herestraat 49, Leuven, 3000, Belgium
| | - Ting Yin
- Department of Radiology, Gasthuisberg University Hospital, Herestraat 49, Leuven, 3000, Belgium
| | - Raymond Oyen
- Department of Radiology, Gasthuisberg University Hospital, Herestraat 49, Leuven, 3000, Belgium
| | - Yicheng Ni
- Department of Radiology, Gasthuisberg University Hospital, Herestraat 49, Leuven, 3000, Belgium
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Shao YL, Arjun B, Leo HL, Chua KJ. Nano-assisted radiofrequency ablation of clinically extracted irregularly-shaped liver tumors. J Therm Biol 2017; 66:101-113. [PMID: 28477903 DOI: 10.1016/j.jtherbio.2017.04.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2017] [Revised: 04/13/2017] [Accepted: 04/13/2017] [Indexed: 02/06/2023]
Abstract
Radiofrequency ablation (RFA) for liver tumors is a minimally invasive procedure that uses electrical energy and heat to destroy cancer cells. One of the critical factors that impedes its successful outcome is the use of inappropriate radiofrequency levels that will not completely destroy the target tumor tissues, resulting in therapy failure. Additionally, the surrounding healthy tissues may suffer from serious damage due to excessive ablation. To address these challenges, this work proposes the employment of injected nanoparticles to thermally promote the ablation efficacy of conventional RFA. A three-dimensional finite difference analysis is employed to simulate the RFA treatment. Based on the data acquired from measured experiments, the simulation results have demonstrated close agreement with experimental data with a maximum discrepancy of within ±8.7%. Several types of nanoparticles were selected to evaluate their influences on liver tissue's thermal and electrical properties. We analysed the effects of nanoparticles on liver RFA via a tumor rending process incorporating several clinically-extracted tumor profiles and vascular systems. Simulations were conducted to explore the temperature difference responses between conventional RFA treatment and one with the inclusion of assisted nanoparticles on several irregularly-shaped tumors. Results have indicated that applying selected nanoparticles with high thermal conductivity and electrical conductivity on the targeted tissue zone promotes heating rate while sustaining a similar ablation zone that experiences lower maximum temperature when compared with the conventional RFA treatment. In sum, incorporating thermally-enhancing nanoparticles promotes heat transfer during the RFA treatment, resulting in improved ablation efficiency.
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Affiliation(s)
- Y L Shao
- Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singapore
| | - B Arjun
- Faculty of Engineering, Engineering Science Programme, National University of Singapore, 9 Engineering Drive 1, Singapore 117 576, Singapore
| | - H L Leo
- Department of Biomedical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singapore
| | - K J Chua
- Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singapore.
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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: 4] [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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Matschek J, Bullinger E, von Haeseler F, Skalej M, Findeisen R. Mathematical 3D modelling and sensitivity analysis of multipolar radiofrequency ablation in the spine. Math Biosci 2017; 284:51-60. [DOI: 10.1016/j.mbs.2016.06.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 06/15/2016] [Accepted: 06/22/2016] [Indexed: 11/28/2022]
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10
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Gemeinhardt O, Poch FG, Hiebl B, Kunz-Zurbuchen U, Corte GM, Thieme SF, Vahldiek JL, Niehues SM, Kreis ME, Klopfleisch R, Lehmann KS. Comparison of bipolar radiofrequency ablation zones in an in vivo porcine model: Correlation of histology and gross pathological findings. Clin Hemorheol Microcirc 2017; 64:491-499. [DOI: 10.3233/ch-168123] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Ole Gemeinhardt
- Department of General, Visceral and Vascular Surgery, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany
| | - Franz G.M. Poch
- Department of General, Visceral and Vascular Surgery, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany
| | - Bernhard Hiebl
- Institute for Animal Hygiene, Animal Welfare and Farm Animal Behaviour, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Urte Kunz-Zurbuchen
- Department of General, Visceral and Vascular Surgery, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany
| | - Giuliano M. Corte
- Institute of Veterinary Anatomy, Freie Universität Berlin, Berlin, Germany
| | - Stefan F. Thieme
- Department of Radiology, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany
| | - Janis L. Vahldiek
- Department of Radiology, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany
| | - Stefan M. Niehues
- Department of Radiology, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany
| | - Martin E. Kreis
- Department of General, Visceral and Vascular Surgery, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany
| | - Robert Klopfleisch
- Institute of Veterinary Pathology, Freie Universität Berlin, Berlin, Germany
| | - Kai S. Lehmann
- Department of General, Visceral and Vascular Surgery, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany
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Saito K, Ito K. Preliminary investigation of numerical estimation of coagulated region generated by interstitial microwave antenna. Int J Hyperthermia 2017; 33:69-73. [DOI: 10.1080/02656736.2016.1220636] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Affiliation(s)
- Kazuyuki Saito
- Center for Frontier Medical Engineering, Chiba University, Chiba, Japan
| | - Koichi Ito
- Center for Frontier Medical Engineering, Chiba University, Chiba, Japan
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12
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Li Z, Zhang K, Lin SM, Mi DH, Cao N, Wen ZZ, Li ZX. Radiofrequency ablation combined with percutaneous ethanol injection for hepatocellular carcinoma: a systematic review and meta-analysis. Int J Hyperthermia 2016; 33:237-246. [PMID: 27701918 DOI: 10.1080/02656736.2016.1237681] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Affiliation(s)
- Zheng Li
- Department of General Surgery, First Clinical Medical College of Lanzhou University, Lanzhou, Gansu Province, PR China
- Department of Oncology, Second People's Hospital of Gansu Province, Lanzhou, Gansu Province, PR China
| | - Kai Zhang
- Department of Infectious Disease, First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, Shaanxi Province, PR China
| | - Shu-Mei Lin
- Department of Infectious Disease, First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, Shaanxi Province, PR China
| | - Deng-Hai Mi
- Department of General Surgery, First Clinical Medical College of Lanzhou University, Lanzhou, Gansu Province, PR China
- Department of Oncology, Second People's Hospital of Gansu Province, Lanzhou, Gansu Province, PR China
| | - Nong Cao
- Department of General Surgery, First Clinical Medical College of Lanzhou University, Lanzhou, Gansu Province, PR China
| | - Zhi-Zhen Wen
- Department of Oncology, Second People's Hospital of Gansu Province, Lanzhou, Gansu Province, PR China
| | - Zhong-Xin Li
- Department of Oncology, Second People's Hospital of Gansu Province, Lanzhou, Gansu Province, PR China
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