ULTRASONIC IMAGING OF THE NONLINEAR PARAMENTERS B/A

本申请的长期目标是开发一种 原型实时超声系统，以成像的非线性 参数B/A用于研究目的。 非线性参数 B/A是一个衡量媒介，支持 超声波相对于机械应变是非线性的 产生于对所施加的机械应力的响应。 B/A 参数反映了介质的性质，很大程度上没有观察到 通过其它成像方法，即，它似乎对 组织结构层次的变化以及 大分子含量 因此，病理条件涉及 组织结构的改变和大分子 重量成分将提供可区分的图像 正常状态和其他不同的成像模式。 反射探头与非线性声相互作用 信号和宽带泵浦波形传播 相反方向，在探头中产生相位变化 在相互作用的空间区域中与B/A成比例。 的 沿接收到的探针的沿着瞬时相位变化是 泵浦波形与空间分布的卷积 B/A沿着相互作用路径。相位调制探头可以 被处理以产生B/A的线图像。 多次反射 以及对泵浦波形的需要 在很宽的波长范围内足够的能量是两个 研究中要解决的问题。

The long term objective of this application is to develop a prototype real-time ultrasonic system to image the nonlinear parameter B/A for research purposes. The nonlinearity parameter B/A is a measure of the degree to which the medium, supporting the ultrasonic wave, is nonlinear relative to the mechanical strain produced in response to applied mechanical stress. The B/A parameter reflects properties of the medium largely not observed by other imaging methods, viz., it appears to be sensitive to changes in the structural hierarachy of tissues and to the macromolecular contents. Thus, pathological conditions involving alteration in tissue architecture and changes in large molecular weight constituents would provide images distinguishable from those of the normal state and different other imaging schemata. The nonlinear acoustic interaction between a reflected probe signal and a broadband pump waveform propagating in the opposite direction, produces phase changes in the probe proportional to B/A in the spatial region of interaction. The instantaneous phase change along the received probe is the convolution of the pump waveform with the spatial distribution of B/A along the interaction path. The phase modulated probe can be processed to produce a line image of B/A. Multiple reflections along the propagation path and the need for pump waveforms with sufficient energy over a wide range of wavelengths are two problems to be dealt with in the study.