Broadband Dielectric Properties of <i>Ex Vivo</i> Bovine Liver Tissue Characterized at Ablative Temperatures

Fallahi, Hojjatollah; Šebek, Jan; Prakash, Punit

doi:10.1109/tbme.2020.2996825

Cited by 28 publications

(41 citation statements)

References 35 publications

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“…For the 50 W experiment, the

of the SP increases from −28.3 dB to −19.2 dB in the first minute. Afterwards, it drops to −39.8 dB at 90 s and then gradually increases to −15 dB at 600 s, which is comparable to 25 W MWA experiment in bovine liver for 600 s, as reported in [ 32 ]. The measurement values represented by green curve are taken from Figure 7 in [ 32 ].…”

Section: Resultssupporting

confidence: 87%

“…Afterwards, it drops to −39.8 dB at 90 s and then gradually increases to −15 dB at 600 s, which is comparable to 25 W MWA experiment in bovine liver for 600 s, as reported in [ 32 ]. The measurement values represented by green curve are taken from Figure 7 in [ 32 ]. Similarly, for the 40 W experiment, the

of the SP increases from −17.3 dB to −14.1 dB in 180 s, which is comparable to the 40 W MWA experiment in bovine liver for 210 s, as reported in [ 32 ].…”

Section: Resultssupporting

confidence: 87%

“…The measurement method has an uncertainty of 10%. The evolution of material properties of SP with temperature are compared with the liver below 80

C as in [ 32 ]. The change in the properties show a similar trend between SP and the liver.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Investigation of Microwave Ablation Process in Sweet Potatoes as Substitute Liver

Khan

Hawlitzki

Taheri

et al. 2021

Sensors

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The microwave ablation technique to destroy cancer tissues in liver is practiced clinically and is the subject of ongoing research, e.g., ablation monitoring. For studies, liver tissue from cattle or pigs is often used as a substitute material. In this work, sweet potato is presented as an alternative material for microwave ablation experiments in liver due to similar material properties. Sweet potatoes as a substitute for liver have the advantages of better handling, easy procurement and stable material properties over time for microwave ablation experiments. The dielectric constant and electrical conductivity of sweet potato are characterized for temperature variation with the help of high-temperature dielectric probe. Furthermore, a test setup is presented for microwave ablation experiments in which a bowtie slot antenna matched to sweet potato is placed on its surface to directly receive the microwave power from a self-developed microwave applicator inserted into a sweet potato 4 cm below the surface antenna. A high-power source was used to excite the microwave powers up to 80 W and a spectrum analyzer was used to measure the signal received by the surface antenna. The experiments were performed in an anechoic chamber for safety reasons. Power at 50 W and 80 W was stimulated for a maximum of 600 s at the 2.45 GHz ISM band in different sweet potato experiments. A correlation is found between the power received by the surface antenna and rise of temperature inside sweet potato; relative received power drops from 1 at 76 ∘C to 0.6 at 88 ∘C (max. temperature) represents a 40% relative change in a 50 W microwave ablation experiment. The received power envelope at the surface antenna is between 10 mW and 32 mW during 50 W microwave ablation. Other important results for 10 min, 80 W microwave ablation include: a maximum ablation zone short axis diameter of 4.5 cm and a maximum ablation temperature reached at 99 ∘C, 3 mm away from the applicator’s slot. The results are compared with the state of the art in microwave ablation in animal liver. The dielectric constant and electrical conductivity evolution of sweet potato with rising temperature is comparable to animal liver in 50–60 ∘C range. The reflection loss of self-developed applicator in sweet potato is below 15 dB which is equal to reflection loss in liver experiments for 600 s. The temperature rise for the first 90 s in sweet potato is 76 ∘C as compared to 73 ∘C in liver with 50 W microwave ablation. Similarly, with 80–75 W microwave ablation, for the first 60 s, the temperature is 98 ∘C in sweet potato as compared to 100 ∘C in liver. The ablation zone short-axis diameter after 600 s is 3.3 cm for 50 W microwave ablation in sweet potato as compared to 3.5 cm for 30 W microwave ablation in liver. The reasons for difference in microwave ablation results in sweet potato and animal liver are discussed. This is the first study to directly receive a signal from microwave applicator during a microwave ablation process with the help of a surface antenna. The work can be extended to multiple array antennas for microwave ablation monitoring.

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“…For the 50 W experiment, the

Section: Resultssupporting

confidence: 87%

of the SP increases from −17.3 dB to −14.1 dB in 180 s, which is comparable to the 40 W MWA experiment in bovine liver for 210 s, as reported in [ 32 ].…”

Section: Resultssupporting

confidence: 87%

See 1 more Smart Citation

Investigation of Microwave Ablation Process in Sweet Potatoes as Substitute Liver

Khan

Hawlitzki

Taheri

et al. 2021

Sensors

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show abstract

“…This study is the starting point for a more extensive dielectric characterization of the adrenal glands at temperatures of interest for MWA. Studies on dielectric properties as function of the temperature have been conducted only in liver so far; and have showed a correlation with the water content of the tissue (varying with the temperature increase) [17]- [20]. A decrease of about 20% in the water content and of 37-33% in the relative permittivity and effective conductivity of the liver when the temperatures overcome 60 °C was observed.…”

Section: Resultsmentioning

confidence: 99%

“…The interactions of the EM field with the surrounding tissues are governed by the relative permittivity and the effective conductivity of the tissues. Therefore, a comprehensive knowledge of the dielectric properties of the biological tissue facilitates accurate modelling of new medical devices as well as human safety studies tissues enables accurate simulations of the antenna performances, the optimization of the antenna geometry and the power delivery settings [17] ̶ [20].…”

Section: Introductionmentioning

confidence: 99%

Dielectric Characterization of Ex Vivo Ovine and Human Adrenal Glands for Microwave Thermal Ablation Applications

Bottiglieri

Shahzad

Donlon

et al. 2021

IEEE J. Electromagn. RF Microw. Med. Biol.

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A graphical representation of the variability of relative permittivity and effective conductivity (S/m) of the functional tissues composing the adrenal gland and related diseases in the frequency range of the microwave thermal ablation techniques. The operating frequencies generally adopted to excite the electromagnetic field by an interstitial antenna are: 915 MHz, 2.45 GHz and 5.8 GHz. Take-Home Messages• Ovine dielectric data are collected, distinguishing between the two functional tissues composing the adrenal gland (cortex and medulla): a sizable difference between the dielectric properties of the two tissues is observed. • Optimized Cole-Cole model of the ovine dielectric properties are presented to allow integration of the data into numerical electromagnetic models. • Human data are collected considering both healthy and diseased adrenal tissues. For the first time, dielectric properties of ex vivo human adrenal glands are measured, presented and compared with data of ex vivo animal models. • The ovine adrenal gland is a feasible model for the optimization of electromagnetic based devices tackling Primary Aldosteronism, such as microwave thermal ablation devices. The ovine model electromagnetically resembles the composition of the human adrenal gland. The ovine model can potentially be adopted in preclinical studies to test the safety and performances of MWA.

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Propagation of Radiofrequency and Microwaves in Tissue

Prakash,

Bottiglieri

2023

The Application of Heat in Oncology

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Broadband Dielectric Properties of Ex Vivo Bovine Liver Tissue Characterized at Ablative Temperatures

Cited by 28 publications

References 35 publications

Investigation of Microwave Ablation Process in Sweet Potatoes as Substitute Liver

Investigation of Microwave Ablation Process in Sweet Potatoes as Substitute Liver

Dielectric Characterization of Ex Vivo Ovine and Human Adrenal Glands for Microwave Thermal Ablation Applications

Propagation of Radiofrequency and Microwaves in Tissue

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