CHARACTERIZATION BY ULTRASOUND--NONLINEARITY PARAMETER

这项拟议的研究的目的是研究超声波 体内的非线性参数B/A(B和A是 状态方程的第二项和第一项分别与 声压和材料密度)。我们的初步研究已经 有关生物学参数的体外测定 材料，包括组织模型。我们已经由两个独立的 方法，即有限幅值法，涉及测量 谐波法和热力学方法涉及到的测量 声速作为静水压力的函数如下：(1) 对于水溶液，B/A与溶质浓度几乎呈线性关系 蛋白质溶液，(2)B/A对分子相对不敏感 在固定浓度下的溶质重量，(3)B/A在6.5-11之间 对于各种软组织，(4)B/A值显著降低 随着组织和组织超细胞结构特征的破坏 细胞结构遭到破坏。因此具有重要意义的信息 有关组织状态的信息被认为包含在 非线性超声传播参数B/A 建议在体内测定一些组织和器官的B/A 并针对其不同的病理状态。这被认为是 在参数可用于诊断成像目的之前是必不可少的 和治疗计划，因为目前还不知道 血管系统参与决定B/A。初步研究将 涉及利用外部化确定B/A作为路径长度的函数 器官，以开发数据库为目的。后续研究将 处理更先进的方法，而不需要手术准备。 将引入病理条件来检查范围 B/A从正常器官到病变器官的变异。这项研究要求 设计和制造合适的换能器系统，以使 测量。 这项研究的结果将是体内B/A值的详细信息 正常和病理组织，长期目标是能够 将此信息用于诊断和治疗目的。

It is the purpose of the proposed study to investigate the ultrasound nonlinearity parameter B/A in vivo (B and A being the coefficients of the second and first terms, respectively, of the equation of state relating acoustic pressure and material density). Our preliminary studies have concerned in vitro determinations of the parameter for biological materials, including tissue models. We have determined by two independent methods, viz., the finite amplitude method involving the measurement of harmonics and the thermodynamic method involving the measurement of the speed of sound as a function of hydrostatic pressure, the following: (1) B/A increases nearly linearly with solute concentration for aqueous solutions of proteins, (2) B/A is relatively insensitive to the molecular weight of the solute at fixed concentrations, (3) B/A ranges from 6.5 to 11 for various soft mammalian tissues, and (4) B/A decreases significantly with destruction of the supracellular architectural features of tissue and with destruction of cellular structure. Thus significant information regarding the state of the tissue is believed to be contained in the nonlinear ultrasonic propagation parameter B/A. It is proposed to determine B/A in vivo for a number of tissues and organs and for different pathological states thereof. This is considered essential before the parameter can be used for diagnostic imaging purposes and for therapeutic treatment planning as it is presently not known how the vascular system is involved in determining B/A. Initial studies will involve determining B/A as a function of path length utilizing exteriorized organs, for the purpose of developing a data base. Subsequent studies will deal with more advanced methods not requiring surgical preparations. Pathological conditions will be introduced to examine the range of variation of B/A from normal to diseased organs. The study requires that appropriate transducer systems be designed and fabricated to make the measurements. The results of this study will be details of in vivo values of B/A of normal and pathological tissues, with the long range goal of being able to utilize this information for diagnostic and therapeutic purposes.