NONLINEAR ULTRASOUND PROPAGATION IN BIOLOGICAL TISSUE

拟议的研究将扩展已发表的同行评审的初步研究。 主要研究者的发现表明1的重要性 MHz，聚焦，有限振幅超声在生物中的传播 组织. 瞬态热电技术将用于 测量体外组织以及 在37 ℃下，作为辐射强度的函数，在10到1000 Wcm-2空间峰-时间峰强度范围。 同时测量 通过快速傅立叶分析的辐射场的光谱内容 校准的宽带水听器的数字化输出将使 谐波产生的作用的检查，在以前的 观察到（由主要研究者）组织超声 吸收系数与强度 实验被提议为 - 源自照射场的分离的有限振幅效应， 从组织内部。 拟议研究的健康相关性 源于多个领域。 虽然超声波目前广泛使用， 在医学诊断和治疗领域的应用， 关于超声波在生物组织中传播的方式 仍然没有答案。 最近的强度测量已经确定， 医学诊断超声仪器利用空间聚焦场 峰-时间峰强度在100至1000 Wcm-2范围内。 的 强度相关的超声吸收的存在可以改变当前的超声吸收 就超声波辐射风险评估发表意见。 的依赖 超声吸收对声强的影响 对许多组织的初步研究表明， 这种现象可能提供一种新的超声组织定征参数 这可以为检查疾病提供一种创新的非侵入性技术 states. 有限振幅超声在内部传播的方式 组织，以及生命系统的生理学改变的程度 目前，这一点引起了人们的兴趣。 这项研究将提供一个 对理解超声波传播的重要贡献， 生物组织和有限振幅声学的重要性 医学超声

The proposed research will extend published peer-reviewed preliminary findings of the Principal Investigator which suggest the importance of 1 MHz, focused, finite amplitude ultrasonic propagation in biological tissue. The transient thermoelectric technique will be employed for the measurement of the absorption coefficient in tissue in vitro as well as in vivo at 37 C as a function of irradiating intensity over the 10 to 1000 Wcm-2 spatial peak-temporal peak intensity range. Simultaneous measurement of the spectral content of the irradiating field via Fast Fourier analyses of the digitized output of a calibrated wide-band hydrophone will enable the examination of the role of harmonic generation in the previously observed (by the Principal Investigator) increase in tissue ultrasonic absorption coefficient with intensity. Experiments are proposed to separate finite amplitude effects originating in the irradiating field and from within the tissue. The health-relatedness of the proposed research stems from a number of areas. While ultrasound is currently in widespread use in the fields of medical diagnosis and therapy, many questions regarding the manner in which ultrasound is propagated in biological tissue remain unanswered. Recent intensity measurements have determined that many medical diagnostic ultrasound instruments utilize focal fields at spatial peak-temporal peak intensities in the 100 to 1000 Wcm-2 range. The presence of intensity-dependent ultrasonic absorption may alter currently held views on ultrasound exposure risk assessment. The dependence of ultrasonic absorption on sound intensity observed in the present preliminary study in a number of tissues suggests such propagation phenomena may offer a new ultrasonic tissue characterization parameter which could offer an innovative noninvasive technique for examining disease states. The manner in which finite amplitude ultrasound propagates within tissue, and the degree to which the physiology of living systems is altered by such exposure, is currently of interest. This study will provide a significant contribution to the understanding of ultrasonic propagation in biological tissue and the importance of finite amplitude acoustics in medical ultrasound.