中文摘要：

高强度聚焦超声（HIFU）是现代医学肿瘤治疗物理疗法的一项重要技术,其原理是通过聚焦方法将大面积超声聚焦换能器辐射出的声能量汇聚于面积极小的聚焦区,使聚焦区获得较强的声能量并利用超声波的热效应在短时间内使病灶部位获得较高的温升,从而使肿瘤组织热凝固坏死.大张角聚焦换能器指的是球面半张角大于16.6°的球壳式聚焦换能器.相对于传统的小张角换能器,大张角聚焦换能器拥有更强的声聚焦效应,聚焦区半径更小,穿透性更好,声能量聚焦效果明显强于小张角换能器,所以可以获得更好的温升.利用Spheroidal Beam Equation（SBE）方程求解大张角聚焦换能器条件下的声场获得空间热源的产热率,然后通过Pennes方程解出大张角聚焦换能器条件下生物组织中的温度场分布.研究不同改变张角方式下大张角聚焦换能器作用下生物组织的温升分布情况,研究结果表明改变换能器的孔径以改变张角时,张角越大温升越大,而改变其焦距以改变张角时,温度变化则相反.实验也验证了换能器孔径变化对生物组织中的温升的影响.

英文摘要：

High intensity focused ultrasound（HIFU）is an important technology of modern medicine physical therapy for cancer treatment.The treatment principle is to focus sound energy generated by a large ultrasonic focusing transducer to achieve a high temperature in a focal area in a short period of time,causing tumor tissue to undergo thermal coagulation necrosis.Sometimes it can achieve high sound intensity（103-104 W·cm-2）by focusing sound energy generated by a large ultrasonic focusing transducer to achieve a high temperature（above 65 ℃）in a focal area in a short period of time,causing tumor tissue to undergo thermal coagulation necrosis thus killing cancerous cells.A focusing transducer with a wide aperture angle is a spherical-shell focusing transducer with a spherical half-angle grea-ter than 16.6°.Because such a wide angle focusing transducer has a larger radiating area,stronger focusing effect,smaller focal area radius and better penetrability than that of a small angle focusing transducer,agreater temperature rise can be generated within a tumor while reducing damage to other normal tissues.In the paper,we use the Spheroidal Beam Equation（SBE）model to calculate the sound field produced by a focusing transducer with a wide aperture angle to obtain heat deposition.The SBE equation includes nonlinearity,diffraction and absorption effects,and can be used to predict the sound field of a transducer with a wide aperture angle.And then we solve the Pennes bioheat equation to obtain the resulting temperature field in a biological tissue.We study the temperature rise induced by a focusing transducer with different wide aperture angles.The results show that the effect of the different way to change the aperture on the temperature rise of the biological tissues is different.When we use the aperture to change the aperature angle,when the apertureis bigger,the temperature rise is bigger.When we use the focus length to change the aperture angle,the result is opposite.Then we conduct the experiment to testify