Simulation study of the effects of HIFU irradiation patterns on thermal lesion to biological tissue

The irradiation pattern of high-intensity focused ultrasound (HIFU) has a significant impact on the therapeutic effect of tumor tissue. In this paper, based on the spheroidal beam equation (SBE) nonlinear acoustics equation and the Pennes bio-heat transfer equation, a thermal lesion prediction model of acoustic-thermal coupling is constructed. The effects of different irradiation patterns, such as HIFU irradiation power and pulse number combination, fractionated heating and sustained heating, and changes in the half-opening angle of a concave spherical ultrasonic transducer on thermal lesion in porcine liver tissue were studied. The research results indicated that the difference in thermal lesion area between the “low power × long pulse” and “high power × short pulse” irradiation pattern was relatively small, and their length and width were almost the same. The area of thermal lesion produced by sustained irradiation of porcine liver tissue by HIFU was significantly larger than the area of thermal lesion produced by fractionated heating. The larger the half-opening angle of the transducer, the larger the thermal lesion area generated by irradiating porcine liver tissue. By selecting appropriate irradiation patterns during HIFU treatment, the optimal thermal lesion area can be obtained in biological tissue.