NONLINEAR ULTRASOUND PROPAGATION IN BIOLOGICAL TISSUE

拟议的研究将延长已发表的同行评议的初步研究 首席调查员的调查结果表明1 MHz聚焦有限幅度超声在生物中的传播 组织。瞬变热电技术将被用于 组织吸收系数的测定及其在体内的应用 在37℃下作为超过10到1000的照射强度的函数的活体 WCM-2空间峰-时间峰强度范围。同时测量 用快速傅里叶分析计算辐射场的光谱含量 校准的宽带水听器的数字化输出将使 对谐波产生在前人研究中作用的考察 (首席调查员)观察到组织超声增加 吸收系数与强度的关系。建议进行实验，以 单独的有限幅度效应起源于辐照场和 从组织内部。拟议研究与健康的相关性 它源于多个领域。虽然超声波目前在全世界都很普遍 在医学诊断和治疗领域的应用，许多问题 关于超声波在生物组织中传播的方式 仍未得到答复。最近的强度测量确定了许多 医学诊断超声仪器利用空间焦域 峰值-时间峰值强度在100到1000wcm-2范围内。这个 依赖于强度的超声吸收的存在可能会改变当前 对超声暴露风险评估持有意见。对…的依赖 超声吸收对声强影响的研究现状 在许多组织中的初步研究表明，这种繁殖 这些现象可能提供一种新的超声组织定征参数 这可能为检查疾病提供一种创新的非侵入性技术 各州。有限幅度超声在内部传播的方式 组织，以及生命系统的生理改变的程度 通过这样的曝光，目前是感兴趣的。这项研究将提供一个 对理解超声传播的重要贡献 生物组织和有限振幅声学在生物医学中的重要性 医学超声波。

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.