【作者】 周玉禄；

【导师】 程建政；

【作者基本信息】 中国科学院研究生院（武汉物理与数学研究所） ， 声学， 2007， 硕士

【摘要】 近年来,用于无创伤治疗肿瘤的高强度聚焦超声(HIFU)技术,已经成为人们关注的热点。大量的实验研究表明,HIFU的治疗机理,主要是利用焦域的声能转化为热能,使病灶组织升温而发生热坏死或灭活。在临床治疗中,生物体大多是由多层组织构成的,HIFU声焦域的位置和形状会受到生物组织结构和发射声强的影响。因此,为了对声焦域准确定位并有效杀灭病灶,研究层状生物媒质中的HIFU声场是非常必要的。本文采用KZK方程描述层状媒质中的聚焦超声波传播,分析了声波传播中媒质衰减、衍射、非线性以及媒质边界的作用。采用时域有限差分数值算法求解KZK方程,并利用该算法计算了凹球面换能器在不同条件下的声场。理论分析了层状生物媒质中的HIFU声场特性变化,同时分析了接近实际HIFU治疗的水-脂肪-肝三层生物组织模型中,HIFU声焦域的变化规律。为了实验验证模拟分析结果,分别测量了水-琼脂-水、水-琼脂-蓖麻油媒质结构中,线性及非线性情况下,声轴平面上的声压分布。实验测量结果和数值模拟结果规律符合较好,验证了理论分析的有效性。理论分析和实验结果均表明,传播媒质结构和发射声压对凹球面换能器HIFU声场分布都有影响,其声焦域特性的变化规律较好地解释了相关文献中关于生物组织中不同辐照强度和辐照深度的损伤实验现象,为分析HIFU治疗时生物组织的声焦域与损伤区域关系提供了依据。更多还原

【Abstract】 In recent years, the high intensity focused ultrasound (HIFU) which is used for non-contacting treating tumor gets hold of more and more attention. The mechanism of HIFU sonication is that temperature rising, caused by sound energy transformation to thermal energy in focused region, results in focus tissue necrotizing or disrupting. During clinical therapy, both tissue conformation and sound intensity have influences on the site and shape of HIFU sound field in the multi-layer biological tissue. In order to locate sound field exactlyand treat focus effectively, the HIFU sound field in layer biological media has been studied.The "KZK" equation, which takes into account the sound absorption, diffraction, nonlinearity and media boundary, was adopted to describe focused ultrasonic wave in layer media in this paper. A time domain numerical solution to the "KZK" equation was used to calculate HIFU sound field of a concave spherical ultrasound transducer in different initial conditions. The variation laws of HIFU sound field and sound focal region in the water-fat-liver layer media, which was used to simulate sound propagation of HIFU sonication were analyzed. Then, some experiments were carried out to validate the numerical simulating results. The pressure distributions of sound axial plane were measured in the layered water-agar pattern-water media and water-agar pattern-castor oil media in different sound pressure conditions. Good agreements with simulation show the availability of theoretical analysis.Both theoretical analyses and experimental results show that absorption of layered media and nonlinearity of high intensity sound pressure have influences on the HIFU sound focal regions. Our research results can explain the damage phenomena in related literatures perfectly. It provides a reference basis for analyzing the relation between sound focal region and lesion of tissue in HIFU sonication.更多还原