Characterization of the dielectric properties of biological tissues using mixture equations and correlations to different states of hydration

Farrugia, Lourdes; Conti, Malcolm Caligari; Farina, Laura; Wismayer, Pierre Schembri; Sammut, Charles V.

doi:10.1088/2057-1976/aafc1a

Cited by 11 publications

(19 citation statements)

References 21 publications

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“…The accurate knowledge of these properties can help predict the electromagnetic energy deposition and the distribution of the temperature increase in the tissue, in order to optimise treatment plans [4][5][6][7]. While dielectric properties have been widely studied [8][9][10][11][12][13][14][15][16][17][18][19][20], less systematised investigations have been conducted to characterise the thermal properties of biological tissues and their changes with temperature.…”

Section: Introductionmentioning

confidence: 99%

Characterisation of Ex Vivo Liver Thermal Properties for Electromagnetic-Based Hyperthermic Therapies

Silva

Bottiglieri

Conceição

et al. 2020

Sensors

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Electromagnetic-based hyperthermic therapies induce a controlled increase of temperature in a specific tissue target in order to increase the tissue perfusion or metabolism, or even to induce cell necrosis. These therapies require accurate knowledge of dielectric and thermal properties to optimise treatment plans. While dielectric properties have been well investigated, only a few studies have been conducted with the aim of understanding the changes of thermal properties as a function of temperature; i.e., thermal conductivity, volumetric heat capacity and thermal diffusivity. In this study, we experimentally investigate the thermal properties of ex vivo ovine liver in the hyperthermic temperature range, from 25 °C to 97 °C. A significant increase in thermal properties is observed only above 90 °C. An analytical model is developed to model the thermal properties as a function of temperature. Thermal properties are also investigated during the natural cooling of the heated tissue. A reversible phenomenon of the thermal properties is observed; during the cooling, thermal properties followed the same behaviour observed in the heating process. Additionally, tissue density and water content are evaluated at different temperatures. Density does not change with temperature; mass and volume losses change proportionally due to water vaporisation. A 30% water loss was observed above 90 °C.

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Section: Introductionmentioning

confidence: 99%

Characterisation of Ex Vivo Liver Thermal Properties for Electromagnetic-Based Hyperthermic Therapies

Silva

Bottiglieri

Conceição

et al. 2020

Sensors

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“…The liquid nature of tissue phantoms allows for significant flexibility in sample measurements, and the container material can vary depending on the application. This paper adopts a mixture equations procedure that is employed by Pollacco et al (2019) which was used for developing tissue-mimicking solutions for muscle and adipose [3]. The study correlates findings from experimental observations and theoretical results by employing both Bruggeman and Maxwell Garnett mixture equations at different hydration states.…”

Section: Introductionmentioning

confidence: 88%

The synthesis of a liver tissue mimicking solution for microwave medical applications

Farhat¹,

Farrugia²,

Farrugia³

et al. 2022

Biomed. Phys. Eng. Express

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This paper presents the synthesis of a mixture solution that is equivalent to ex-vivo liver tissue dielectric characteristics between 500 MHz and 5 GHz. The mimicking solution was synthesized using concentrations of two chemicals, the solute which is referred to as the inclusion phase and the solvent, referred to as the host phase. The inclusion phase consisted of bovine serum albumin (BSA) powder and the host phase was comprised of a phosphate-buffered saline (PBS) solution with a concentration of Triton X-100 (TX-100). The dielectric properties of these two phases were substituted into Bruggeman’s two-phase mixture equation to estimate the dielectric properties of an excised liver tissue. Furthermore, the study exploits Bruggeman’s equation to investigate the impact of tissue dehydration levels on the dielectric properties of an excised tissue. The effect of dehydration has been characterised as a function of time based on the loss-on-drying technique (a substance is heated until it is completely dry). Dielectric parameters were measured as a function of frequency using a slim form open-ended coaxial probe at a constant room temperature of circa 25◦ C. Measured dielectic data were fitted to the Cole-Cole model and good agreement with the mimicking solutions was obtained. These results indicate that these solutions can be used to model the human body phantoms for microwave medical applications.

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“…Relevant to the effective medium theory, a mixing rule was employed to model the dielectric properties of the tissue under test. This method has resulted in accurate mimicking solutions of in vivo and ex vivo tissue in different states of hydration [15]. Assuming the tissues as a two-phase mixture, the models were generated considering a dry inclusion phase and a fluid-based host environment.…”

Section: B Tissue Mimic Preperationmentioning

confidence: 99%

An investigation into the use of CALNN capped gold nanoparticles for improving microwave heating

Bonello

Rossi

Thanh

et al. 2019

2019 International Conference on Electromagnetics in Advanced Applications (ICEAA)

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The use of microwaves for both therapeutic and diagnostic applications has become an accepted alternative in the clinics. For diagnostics, gold (Au) nanoparticles have been used for imaging tumour vasculature and also served as potential diagnostic markers for cancer. [1] In high-frequency therapeutic applications, two different treatments exist; hyperthermia and ablation. [2] In hyperthermia, the tumour tissue is heated to supra-physiological temperatures, making it more susceptible to traditional treatment methods such as chemotherapy and radiotherapy. This type of treatment could be administered externally. However, there still remains a challenge to focus the heating to particular areas which need to be treated, while avoiding unwanted hotspots. To date, numerous methods have been used to focus the heat from different antennas. A novel technique which is being investigated is the use of nanoparticles to improve focusing and thus achieve better localised heating effect. A previous study by Cardinal et al. [3] showed that at RF-frequencies, remarkable improvements resulted from using Au nanoparticles. In this work, the use of CALNN peptide capped Au nanoparticles for the focusing of microwaves at 2.45 GHz is investigated. The CALNN capped Au nanoparticles were prepared as described elsewhere. [4] Au nanoparticles were added to tissue mimicking solutions (such as muscle, liver or fat) to compare their dielectric properties with the those of the control (without Au nanoparticles). The frequency range investigated was from 400 MHz to 20 GHz. During this study, various concentrations, particle sizes and shapes of Au nanoparticles were considered. The study also investigated the heating rates of the pseudo-biological tissue samples and how these varied with the addition of the nanoparticles. The outcome of this study will determine the viability of using CALNN capped Au nanoparticles to assist in the focusing of microwave radiation during microwave hyperthermia.

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Characterization of the dielectric properties of biological tissues using mixture equations and correlations to different states of hydration

Cited by 11 publications

References 21 publications

Characterisation of Ex Vivo Liver Thermal Properties for Electromagnetic-Based Hyperthermic Therapies

Characterisation of Ex Vivo Liver Thermal Properties for Electromagnetic-Based Hyperthermic Therapies

The synthesis of a liver tissue mimicking solution for microwave medical applications

An investigation into the use of CALNN capped gold nanoparticles for improving microwave heating

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