【作者】 李全义；

【导师】 李发琪；

【作者基本信息】 重庆医科大学 ， 生物医学工程， 2009， 硕士

【摘要】 高强度聚焦超声(high intensity focused ultrasound,HIFU)是一种将超声波聚焦到病变组织内,使焦点处靶组织产生局部高温而发生凝固性坏死,但对周围组织无损伤,从而达到原位“切除”病变组织的目的,已用于多种实体肿瘤和非肿瘤疾病的治疗。但应用HIFU治疗肿瘤时发现,位于深部或体积大的肿瘤,HIFU治疗的时间明显延长,治疗效率不够理想。国内外通过各种方式对提高HIFU治疗效率进行了研究,其中开发新型换能器是一种行之有效的方法。传统的HIFU换能器工作在单一频率模式下,有研究表明谐波叠加和差频相干这两种方式,在损伤组织效率中均有良好效果,都值得进一步研究。考虑到差频相干模式具有基频和差频均可较灵活选择的优点,本文通过瑞利积分与瑞利积分的线性叠加算法,以凹球面双频聚焦超声换能器为例,对声场进行了物理声学分析,探讨了换能器分割面积、频差、衰减与非线性对双频聚焦超声声场的影响。结果表明选择适当的频差与分割面积可以有效地增大组织损伤焦斑,在时间-空间特性上,由于声波的干涉所致,瞬态焦域呈“糖葫芦”状,并随时间此消彼长地移动变化,但从时间统计来看,其声场是空间分布均匀的,并且声焦域内声压分布较单频均匀;随着组织衰减和声场非线性的增强,声焦域从椭球型变为“头大尾细”的蝌蚪型;与单频相比较,双频聚焦超声焦域内声压分布更加均匀,这将在聚焦超声治疗中防止焦域中心温度过高而引起组织碳化。从焦域形态来看,双频聚焦超声较单频声焦域增大,且主要表现在长轴上,这将有利于提高治疗效率,但同时也有可能引起长短轴之比增大所引起的安全性影响。在实验上,通过激光声场检测与对离体组织损伤的初步实验进行了验证。更多还原

【Abstract】 High intensity focused ultrasound(HIFU) treatment have been used in sorts of tumor and non-tumor disease.The tissues of target region would absorb the energy of the supersonic wave and be destroyed,while the tissues out of the target region would not be destroyed.But during the tumor therapy especially those deeply located in body or with a large volume, HIFU was a time-consuming therapeutic method and the curative effect was far from ideal.It was researched that how to enhancement the therapeutic efficiency of HIFU by a variety of ways in international.One of the effective ways is developing new transducer.Traditional HIFU transducer works as the mode of single frequency. Some researches show that harmonic and difference frequency coherent superposition of these two methods,at both organizational efficiency injury with good results,are worthy of further study.Take in account,it was very flexible to choose fundamental frequency and difference frequency in the mode of interference of difference frequency.The effect of partition areas proportion of transducer surface、difference frequency、attenuation and non-linear to dual-frequency acoustic field based on Rayleigh integral were discussed in this paper.The results show that with the proper choosing of partition area proportion and frequency difference,the injury sound focal region of dual-frequency acoustic field is larger than that of a single frequency significantly,and the distribution of sound pressure in acoustic focus region(AFR) was uniformity.The AFR change from ellipsoid to tadpole with the strengthen of attenuation and non-linear;The spatial and temporal characteristics of dual-frequency focused acoustic field of the differential frequency coherence mode were investigated too.Last,we did some experiments to detection the acoustic field and lesion in tissue in vitro for dual-frequency focused transducer.更多还原