Influence of Blood Vessels on Temperature during High-Intensity Focused Ultrasound Hyperthermia Based on the Thermal Wave Model of Bioheat Transfer

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.

Sequential Administrations of a Vascular-Disrupting Agent, High-Intensity Focused Ultrasound, and a Radioactively labeled Necrosis Avid Compound for Eradicating Solid Malignancies

“…Previously, clinicians were concerned that blood flow in tissues could dissipate the generated heat during HIFU treatment, causing insufficient thermal effects for tumor ablation. 20 Such a heat sink effect may spare a large number of live tumor cells after HIFU treatment, leading to recurrence later. Further increasing the power output to increase the temperature may cause skin burns and pain, making analgesic and fractionated treatment compulsory.…”

“…The disadvantages of HIFU include (i) blood flow within the tissue causes a heat sink effect during HIFU, 20 which may reduce the thermal energy crucial for thorough coagulative necrosis and leave residual tumor cells that may regrow and (ii) cancer cells between coagulated foci may escape from thermal damage irrespective of the density of the HIFU matrix.…”

Micro/nano-bubble-assisted ultrasound to enhance the EPR effect and potential theranostic applications

“…When the distance between the surface of the blood vessel and the focal point is 2.5 mm, the temperature at the focal point was saturated after approximately 50 s of radiation, and the maximum cooling caused by the blood flow was approximately 0.5 °C when the supply of radiation was ceased 90. Based on the thermal wave model of bioheat transfer, Tan et al numerically investigated the influence of blood vessels on temperature during high-intensity focused ultrasound hyperthermia 91. The results showed that a longer duration of thermal relaxation leads to the production of smaller thermal lesions.…”

Effects of Thermal Relaxation on Temperature Elevation in Ex Vivo Tissues During High Intensity Focused Ultrasound

“…Through a voltage-calibration method, Zhang et al investigated the feasibility of TWMBT in the radiofrequency ablation (RFA) simulation, the results suggested that the prediction of TWMBT was 0.55 °C more accurate than Pennes equation, declared that TWMBT could be used as an alternative in the simulation of long-duration high intensity RFA [13]. In recent years, TWMBT also has been employed to study bio-heat transfer during HIFU [14][15][16][17]. Liu et al [14] and Gupta et al [16] used TWMBT to estimate the temperature elevation induced by HIFU in biological tissues.…”