Dielectric properties of RF heated<i>ex vivo</i>porcine liver tissue at 480 kHz: measurements and simulations

Macchi, Edoardo Gino; Gallati, Mario; Braschi, Giovanni; Persi, Elisabetta

doi:10.1088/0022-3727/47/48/485401

Cited by 18 publications

(17 citation statements)

References 39 publications

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“…and Kwon et al . demonstrate similar irreversible changes at RF frequencies above ~60 °C (51, 52); Macchi showed conductivity dependence on rate of heating in addition to temperature (46). These time- and temperature-dependent changes have been modeled by an Arrhenius relationship in several studies (46, 51, 55), which may be preferred in some applications to a simple dependence on temperature alone.…”

Section: Temperature Dependence Of Electrical Propertiesmentioning

confidence: 88%

“…Extensive literature has been around for more than 30 years presenting tabulated dielectric properties of tissues in the frequency range from 10 kHz to 10 GHz around body temperatures (20–40°C) and have been reported by Gabriel et al ., Duck et (46) al . and other researchers (42–44, 47–50); however, the temperature dependence of these frequency-dependent dielectric properties in the RF and MW frequency range has only been studied more recently.…”

Section: Temperature Dependence Of Electrical Propertiesmentioning

confidence: 99%

“…Macchi et al . measured dielectric properties of liver ex-vivo up to 100 °C and found increasing conductivity with temperature; in addition, they found a dependence on heating rate which could be modeled by an Arrhenius relationship (46). McRae et al .…”

Section: Temperature Dependence Of Electrical Propertiesmentioning

confidence: 99%

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Review of Temperature Dependence of Thermal Properties, Dielectric Properties, and Perfusion of Biological Tissues at Hyperthermic and Ablation Temperatures

Rossmanna

Haemmerich

2014

Crit Rev Biomed Eng

299

211

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The application of supraphysiological temperatures (>40°C) to biological tissues causes changes at the molecular, cellular, and structural level, with corresponding changes in tissue function and in thermal, mechanical and dielectric tissue properties. This is particularly relevant for image-guided thermal treatments (e.g. hyperthermia and thermal ablation) delivering heat via focused ultrasound (FUS), radiofrequency (RF), microwave (MW), or laser energy; temperature induced changes in tissue properties are of relevance in relation to predicting tissue temperature profile, monitoring during treatment, and evaluation of treatment results. This paper presents a literature survey of temperature dependence of electrical (electrical conductivity, resistivity, permittivity) and thermal tissue properties (thermal conductivity, specific heat, diffusivity). Data of soft tissues (liver, prostate, muscle, kidney, uterus, collagen, myocardium and spleen) for temperatures between 5 to 90°C, and dielectric properties in the frequency range between 460 kHz and 3 GHz are reported. Furthermore, perfusion changes in tumors including carcinomas, sarcomas, rhabdomyosarcoma, adenocarcinoma and ependymoblastoma in response to hyperthmic temperatures up to 46°C are presented. Where appropriate, mathematical models to describe temperature dependence of properties are presented. The presented data is valuable for mathematical models that predict tissue temperature during thermal therapies (e.g. hyperthermia or thermal ablation), as well as for applications related to prediction and monitoring of temperature induced tissue changes.

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Section: Temperature Dependence Of Electrical Propertiesmentioning

confidence: 88%

Section: Temperature Dependence Of Electrical Propertiesmentioning

confidence: 99%

See 1 more Smart Citation

Review of Temperature Dependence of Thermal Properties, Dielectric Properties, and Perfusion of Biological Tissues at Hyperthermic and Ablation Temperatures

Rossmanna

Haemmerich

2014

Crit Rev Biomed Eng

299

211

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“…In previous studies, the simulation of RFA around 500 kHz was implemented by ignoring the displacement current, and the overall system was treated like a direct current (DC) circuit governed by electrostatic equations. The tissue was considered to be purely resistive [1,4,5,7,8]. It has been argued that at $500 kHz the wavelength is much longer than the liver, and the displacement current can be neglected according to liver tissue properties.…”

Section: Introductionmentioning

confidence: 99%

AC measurements and simulations of hepatic radiofrequency ablation

Chang

Kuo

Lee

2021

International Journal of Hyperthermia

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Introduction: The radiofrequency ablation (RFA) of liver cancer is a desirable treatment option, as it is minimally invasive. An accurate numerical simulation can greatly help physicians better plan their surgical protocols. Previously, the displacement current in the RFA process was considered negligible, and therefore RFA simulation was modeled as a direct current (DC) system instead of an alternating current (AC) system. Our study investigated the hypothesis that the displacement current in the RFA process should not always be considered negligible. Methods: AC measurements of ex vivo bovine liver ablation were performed, and numerical simulations were also conducted to test the hypothesis that the relative permittivity would significantly decrease after the liver tissue reached a high temperature. Results: The displacement current was observed to be a sizable fraction of the conduction current, especially before the onset of the first pause. The simulation results indicated that the relative permittivity is likely to decrease to several hundred or lower at elevated temperatures. Conclusions: Our study results suggest that the DC model may be inadequate, especially before the first roll-off and that additional information could be available during RFA treatment by considering the AC nature of RFA, which could lead to improved numerical simulation. Additional measurements of tissue parameters are needed to reach the full potential of the AC model for further development of ablation control.

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“…These PEF therapies should be evaluated in a model that replicates the electrical and thermal properties of in vivo tissue as well as the geometric size so that instruments intended for clinical use can be evaluated without modification. Historically, ex vivo bovine liver has served this role, [29][30][31][32][33] and recent developments in organ preservation 34 have enabled the use of viable ex vivo liver tissue for evaluating PEF therapies. 11,23,35 However, precise computational quantification of thermal injury in these models can be challenging due to limited contrast between the injured and normal tissue or the need for expensive thermometry methods (e.g.…”

Section: Introductionmentioning

confidence: 99%

Thermochromic Tissue Phantoms for Evaluating Temperature Distribution in Simulated Clinical Applications of Pulsed Electric Field Therapies

Sano

DeWitt

2020

Bioelectricity

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Background: Irreversible electroporation (IRE) induces cell death through nonthermal mechanisms, however, in extreme cases, the treatments can induce deleterious thermal transients. This study utilizes a thermochromic tissue phantom to enable visualization of regions exposed to temperatures above 60°C. Materials and Methods: Poly(vinyl alcohol) hydrogels supplemented with thermochromic ink were characterized and processed to match the electrical properties of liver tissue. Three thousand volt high-frequency IRE protocols were administered with delivery rates of 100 and 200 ls/s. The effect of supplemental internal applicator cooling was then characterized. Results: Baseline treatments resulted thermal areas of 0.73 cm 2 , which decreased to 0.05 cm 2 with electrode cooling. Increased delivery rates (200 ls/s) resulted in thermal areas of 1.5 and 0.6 cm 2 without and with cooling, respectively. Conclusions: Thermochromic tissue phantoms enable rapid characterization of thermal effects associated with pulsed electric field treatments. Active cooling of applicators can significantly reduce the quantity of tissue exposed to deleterious temperatures.

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Dielectric properties of RF heatedex vivoporcine liver tissue at 480 kHz: measurements and simulations

Cited by 18 publications

References 39 publications

Review of Temperature Dependence of Thermal Properties, Dielectric Properties, and Perfusion of Biological Tissues at Hyperthermic and Ablation Temperatures

Review of Temperature Dependence of Thermal Properties, Dielectric Properties, and Perfusion of Biological Tissues at Hyperthermic and Ablation Temperatures

AC measurements and simulations of hepatic radiofrequency ablation

Thermochromic Tissue Phantoms for Evaluating Temperature Distribution in Simulated Clinical Applications of Pulsed Electric Field Therapies

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