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Zhang B, Moser MAJ, Zhang EM, et al. A new approach to feedback control of radiofrequency ablation systems for large coagulation zones. Int J Hyperthermia. 2016;33(4):367-377doi: 10.1080/02656736.2016.1263365.
Zhang, B., Moser, M. A. J., Zhang, E. M., Luo, Y., & Zhang, W. (2017). A new approach to feedback control of radiofrequency ablation systems for large coagulation zones. International journal of hyperthermia : the official journal of European Society for Hyperthermic Oncology, North American Hyperthermia Group, 33(4), 367-377. https://doi.org/10.1080/02656736.2016.1263365
Zhang, Bing, et al. "A new approach to feedback control of radiofrequency ablation systems for large coagulation zones." International journal of hyperthermia : the official journal of European Society for Hyperthermic Oncology, North American Hyperthermia Group vol. 33,4 (2017): 367-377. doi: https://doi.org/10.1080/02656736.2016.1263365
Zhang B, Moser MAJ, Zhang EM, Luo Y, Zhang W. A new approach to feedback control of radiofrequency ablation systems for large coagulation zones. Int J Hyperthermia. 2017 Jun;33(4):367-377. doi: 10.1080/02656736.2016.1263365. Epub 2016 Dec 06. PMID: 27868461.
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Int J Hyperthermia. 2017 Jun;33(4):367-377. doi: 10.1080/02656736.2016.1263365. Epub 2016 Dec 06.

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

International journal of hyperthermia : the official journal of European Society for Hyperthermic Oncology, North American Hyperthermia Group

Bing Zhang, Michael A J Moser, Edwin M Zhang, Yigang Luo, Wenjun Zhang

Affiliations

  1. a CISR Lab , East China University of Science and Technology , Shanghai , China.
  2. b Division of Biomedical Engineering , University of Saskatchewan , Saskatoon , Canada.
  3. c Department of Surgery , University of Saskatchewan , Saskatoon , Canada.
  4. d Division of Vascular & Interventional Radiology, Department of Medical Imaging , University of Toronto , Toronto , Canada.
  5. e Department of Mechanical Engineering , University of Saskatchewan , Saskatoon , Canada.

PMID: 27868461 DOI: 10.1080/02656736.2016.1263365

Abstract

AIM: The aim of this study was to investigate the feasibility of achieving relatively large coagulation zones (i.e. ≥3 cm in diameter) with radiofrequency ablation (RFA) by using a broad control system.

MATERIALS AND METHODS: A broad control system consists of information such as (i) the area of the tumour tissue for feedback control, (ii) the set-point temperature and (iii) the control law. The proposed approach has advanced knowledge in (i) and (ii) in particular. RFA is known to be limited by tissue dehydration that occurs around the electrode, which results in impedance such that no further energy can be delivered to the tissues. We proposed the notion of "energy gate", an area on the electrode, which is not covered by the dehydrated tissue and through which energy can still be delivered to the surrounding tissues. Given a specific size of energy gate, both (i) the area of the tissue in which the temperature is monitored and (ii) the set-point temperature were determined. A reliable finite element model or simulator for a commercially available electrode was used and the tissue surrounding the RFA electrode was divided into three areas for a comprehensive study of the issues (i) and (ii). Porcine liver tissue (30 specimens in total) and a custom-made RFA device with a RF power generator (100 W and 460 ± 30 kHz) and a Covidien cool-tip electrode (17 gauge and 30 mm exposure) were used to validate the findings regarding the area of the tissue for feedback control and the set-point temperature.

RESULTS: The size of coagulation zone achieved was maximised when the area of tissue surrounding the middle part of the active tip (i.e. Point 7) was used for feedback control and when the set-point temperature was set to 90

CONCLUSION: The judicious selection of the control area within the biological tissue for temperature monitoring and the set-point temperature for feedback control is critical in increasing the size of the coagulation zone in the treatment of RFA.

Keywords: Finite element model; large coagulation zone; liver tumour; mono-polar electrode; temperature-controlled radiofrequency ablation

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