Numerical study of non-Fourier thermal ablation of benign thyroid tumor by focused ultrasound (FU)

Estimation of thermal response of tumoral tissue to the hyperthermia treatment is an important factor for increasing the effectiveness of therapeutic method. In this study, focused ultrasound (FU) is used to produce irreversible thermal damage for the treatment of benign thyroid tumor. To this end, a multi-layer model of the neck including internal organs from the skin toward the thyroid gland is exposed to ultrasound irradiation at powers of 3 W, 5 W, and 7 W and at the frequency of 3 MHz. It is observed that the acoustic pressure is noticeably increased by considering different neck's internal organs. The temperature profile is obtained by taking into account the non-Fourier thermal response for the thyroid gland. The thermal wave model and dual phase lag model are utilized along with the traditional Pennes bio-heat transfer model. Studying the temperature profile at 3 W power by non-Fourier thermal models illustrates that the maximum temperature with time delays of 11.32, 5.66 and 2.86 s is 20.51%, 14.1% and 8.65% lower than the corresponding value by the Fourier model. Deviation from the Fourier results is increased for higher powers of transducer. It is also inferred that in the presence of time delays, temperature variation in the focal area becomes smoother. Effect of non-Fourier heat transfer is studied on the area of necrotic tumoral region. It is concluded that region with irreversible thermal damage shrinks by considering the phase lags in the way that in 3 W power and 5.66 s time delay, no necrosis of the thyroid nodule is observed. (C) 2019 Nalecz Institute of Biocybernetics and Biomedical Engineering of the Polish Academy of Sciences. Published by Elsevier B.V. All rights reserved.