چكيده به لاتين
Today, in advanced and growing societies, cancer is a major and fundamental problem for human health. Conventional methods such as surgery, chemotherapy, radiation therapy, etc., which are used to treat cancer, have limitations that have led to the development and use of new therapies. One of these methods is hyperthermia. Hyperthermia uses one of the heat sources called high-intensity focused ultrasound or hifu to generate heat in the tumor tissue. The basis of Hyperthermia with the hifu method is the concentration of waves in the center of the tumor and the production of heat (by absorbing ultrasound waves and converting it to heat) in it, which increases the temperature in the focal area and destroys the tumor tissue in that area. The aim of this study is to investigate the temperature distribution and the degree of thermal damage caused by hyperthermia with hifu in the absence and presence of a thermally significant blood vessel in biological tissue. For this purpose, tissue without and with vessel modeling has been performed in a 2D-Axisymmetric model. Then, to achieve the field of acoustic pressure, acoustic intensity, and heat generated in the tissue, the propagation of the waves has been done with Helmholtz linear and KZK nonlinear equations. Now, to obtain the temperature results, the Pennes bioheat transfer equation, the thermal wave model for bioheat transfer, and the dual phase lag bioheat model have been used. In the two models of thermal wave and dual phase lag, thermal inertia term and thermal inertia and thermal interaction terms are considered, respectively, which lead to increasing the accuracy of the results for future clinical applications. The Arrhenius model has been also used to obtain the results related to the degree of damage. The results of this study show that the thermal relaxation time and the second delay time play a key role in the temperature distribution and the degree of thermal damage in the tissue. For example, in linear wave propagation and in the case of tissue without vessel, the temperature values in the Pennes, thermal wave and dual phase lag models are 74.2 ° C, 62.74 ° C and 48.35, respectively that these values prove the effect of the times in the thermal wave and the dual phase lag models on the temperature compared to the Pennes model. The larger these two times, the lower the temperature and degree of damage in the tissue in both the thermal wave and the dual phase lag models than in the Pennes model. In addition, the results of examining the parameters of the vessel, such as the radius of the vessel and the average velocity of blood flow in it, indicate that the vessel radius significantly affects the temperature and the degree of damage, while the average velocity has a slight effect on them.
