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

Zhang, Bing; Möser, Michael; Zhang, Edwin M.; Luo, Yigang; Zhang, Wenjun

doi:10.1080/02656736.2016.1263365

Cited by 37 publications

(16 citation statements)

References 54 publications

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“…The fitted thermal conductivity of the prefreezing tissue was 0.47 W/mÁK, representing the apparent or effective thermal conductivity, which was close to the reported data for normal liver tissue [33][34][35]. The fitted blood perfusion rate of normal tissue during the RF heating process was 0.053 l/s, which was greater than that reported in the literature [39,40].…”

Section: Thermal Conductivity and Blood Perfusion Ratesupporting

confidence: 80%

“…This is to be expected since the tissue composition has not been changed by the pre-freezing process. The blood perfusion rate of the in vivo liver in the physiological state is quite different, ranging from 0.0064 l/s to 0.016 l/s [39,40]. The fitted blood perfusion rate of normal tissue during the RF heating process was 0.053 l/s, which was greater than that reported in the literature.…”

Section: Discussionmentioning

confidence: 55%

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Study of enhanced radiofrequency heating by pre-freezing tissue

Zhang

Zou

et al. 2018

International Journal of Hyperthermia

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In our previous animal model study, we found that radiofrequency (RF) ablation of pre-frozen tumor resulted in improved therapeutic effects. To understand the underlying mechanisms and optimize the treatment protocol, the RF heating pattern in pre-frozen tissue was studied in this paper. Both ex vivo and in vivo experiments were conducted to compare the temperature profiles of RF heating with or without pre-freezing. Results showed that the heating rate of in vivo tissues was significantly higher with pre-freezing. However, little difference was observed in the heating rate of ex vivo tissues with or without pre-freezing. In the histopathologic analysis of in vivo tissues, both a larger ablation area and a wider transitional zone were found in the tissue with pre-freezing. To investigate the cause for the enhancement in RF heating, the parameters affecting the tissue temperature rise were studied. It was found that the electrical conductivity of in vivo tissue with pre-freezing was much higher at low frequencies, but little difference was found at the 460 kHz frequency commonly used in clinical applications. A finite element model for RF heating was developed and validated to fit the thermal conductivity of in vivo tissue including effects of pre-freezing and the associated blood perfusion rate. Results showed that the enhancement of the heating rate was primarily attributed to the decreased blood perfusion rate in the tissue with vascular damage caused by pre-freezing. The ablation volume was increased by 104% due to the reduced heat dissipation.

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Section: Thermal Conductivity and Blood Perfusion Ratesupporting

confidence: 80%

Section: Discussionmentioning

confidence: 55%

Study of enhanced radiofrequency heating by pre-freezing tissue

Zhang

Zou

et al. 2018

International Journal of Hyperthermia

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“…Changes to the RF energy delivery can be executed either in a pulse manner by repeatedly switching on and off the RF generator 38‐40 or continuously via some feedback controller such as the proportional‐integral‐derivative controller 41‐44 . More recently, a broad control system that takes into consideration the area of the tumour tissue and the tumour temperature was proposed 45 . The broad control system was capable of increasing the coagulation zone size provided that the selection of tumour area and the threshold temperature were appropriately selected.…”

Section: Methodsmentioning

confidence: 99%

Thermal and thermal damage responses during switching bipolar radiofrequency ablation employing bipolar needles: A computational study on the effects of different electrode configuration, input voltage and ablation duration

Cheong

Ooi

2020

Numer Methods Biomed Eng

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Recent studies have demonstrated the effectiveness of switching bipolar radiofrequency ablation (bRFA) in treating liver cancer. Nevertheless, the clinical use of the treatment remains less common than conventional monopolar RFA – likely due to the lack of understanding of how the tissues respond thermally to the switching effect. The problem is exacerbated by the numerous possible switching combinations when bRFA is performed using bipolar needles, thus making theoretical deduction and experimental studies difficult. This article addresses this issue via computational modelling by examining if significant variation in the treatment outcome exists amongst six different electrode configurations defined by the X‐, C‐, U‐, N‐, Z‐ and O‐models. Results indicated that the tissue thermal and thermal damage responses varied depending on the electrode configuration and the operating conditions (input voltage and ablation duration). For a spherical tumour, 30 mm in diameter, complete ablation could not be attained in all configurations with 70 V input voltage and 5 minutes ablation duration. Increasing the input voltage to 90 V enlarged the coagulation zone in the X‐model only. With the other configurations, extending the ablation duration to 10 minutes was found to be the better at enlarging the coagulation zone.

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“…Fang et al proposed a novel expandable electrode to re-distribute electric field for avoiding roll-off [7], [8]. Zhang et al proposed a novel feedback control method to avoid roll-off by controlling RF power delivery [9]. Meanwhile, other authors have demonstrated that the injection of normal saline solution or diluted hydrochloric acid (HCl) can efficiently delay roll-off occurrence and lead to achieving larger ablative zones [10], [11].…”

Section: Introductionmentioning

confidence: 99%

A Novel Method to Increase Tumor Ablation Zones With RFA by Injecting the Cationic Polymer Solution to Tissues: In Vivo and Computational Studies

Fang

Möser

Zhang

et al. 2020

IEEE Trans. Biomed. Eng.

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This study aims to examine, for the first time, the introduction of cationic polymer solutions to improve radiofrequency ablation (RFA) in terms of a potentially enlarged ablation zone. Methods: By using in vivo and computational RFA studies, two cationic polymers, Chitooligosaccharides (COS) and carboxymethyl chitosan (CMC), diluted in deionized water, were injected into tissues separately surrounding the RF bipolar electrode prior to power application. A total of 9 rabbits were used to 1) measure the increase in electrical conductivity of tissues injected with the cationic polymer solutions, and 2) explore the enhancement of the ablation performance in RFA trials. A computer model of RFA comprising a model of the solution diffusion with an RF thermal ablation model was also built, validated by the in vivo experiment, to quantitatively study the effect of cationic polymer solutions on ablation performances. Results: Compared to the control group, the electrical conductivity of rabbit liver tissues was increased by 42.20% (0.282 ± 0.006 vs. 0.401 ± 0.048 S/m, P = 0.001) and 43.97% (0.282 ± 0.006 vs. 0.406 ± 0.042 S/m, P = 0.001) by injecting the COS and CMC solution at the concentration of 100 mg/mL into the tissues, denoted COS D W 100 and CMC D W 100 , respectively. Consequently, the in vivo experiments show that the ablation zone was enlarged by 95% (47.6 ± 6.3 vs. 92.6 ± 11.5 mm 2 , P <

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

Abstract: 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.

Cited by 37 publications

References 54 publications

Study of enhanced radiofrequency heating by pre-freezing tissue

Study of enhanced radiofrequency heating by pre-freezing tissue

Thermal and thermal damage responses during switching bipolar radiofrequency ablation employing bipolar needles: A computational study on the effects of different electrode configuration, input voltage and ablation duration

A Novel Method to Increase Tumor Ablation Zones With RFA by Injecting the Cationic Polymer Solution to Tissues: In Vivo and Computational Studies

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