Abstract
The coupled effects of blood vessels and thermal relaxation time on temperature and thermal lesion region in biological tissue during high-intensity focused ultrasound (HIFU) hyperthermia are numerically investigated. Considering the non-Fourier behavior of heat conduction in biological tissue, the traditional Pennes bioheat equation was modified to thermal wave model of bioheat transfer (TWMBT). Consequently, a joint physical model, which combines TWMBT for tissue and energy transport equation for blood vessel, is presented to predict the evolution of temperature and the thermal lesion region. In this study, pulsatile blood flow is first introduced into numerical study of HIFU hyperthermia, and thermal relaxation time, ultrasonic focus location, blood vessel radius, and blood flow velocity are all taken into account. The results show that the thermal relaxation time plays a key role in the temperature and the thermal lesion region. Larger thermal relaxation time results in lower temperature and smaller thermal lesion region, which indicates that TWMBT leads to lower temperature and smaller thermal lesion region compared to Pennes bioheat transfer model. In addition, we found that the ultrasonic focus location and blood vessel radius significantly affected the temperature and thermal lesion region, while the heartbeat frequency and amplitude factor of pulsating blood flow as well as the average velocity of blood flow had only a slight effect.
Highlights
High-intensity focused ultrasound (HIFU) is a promising noninvasive technology, which can rapidly produce a local high temperature of more than 70∘C in target tissues for the purpose of thermal ablation [1, 2]
The effects of blood vessels on temperature and thermal lesion region based on thermal wave model of bioheat transfer (TWMBT) during HIFU hyperthermia will be comprehensively investigated, including various factors associated with blood vessels
The greater thermal relaxation time leads to smaller thermal lesion region
Summary
High-intensity focused ultrasound (HIFU) is a promising noninvasive technology, which can rapidly produce a local high temperature of more than 70∘C in target tissues for the purpose of thermal ablation [1, 2]. To our knowledge, few studies have been done on HIFU hyperthermia employing TWMBT until now, especially considering biological tissue with blood vessel. Several numerical studies of the effects of blood vessels on temperature and thermal lesion region in ultrasound hyperthermia had attracted the interests of many researchers. The temperature field computation was based on Pennes bioheat transfer model in most previous studies, neglecting the non-Fourier effects on thermal transfer, and the quantitative effects of the blood vessel on temperature and thermal lesion region in the heated tissue are still ambiguous. The effects of blood vessels on temperature and thermal lesion region based on TWMBT during HIFU hyperthermia will be comprehensively investigated, including various factors associated with blood vessels. We believe that this study is significant for HIFU hyperthermia
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