ULTRASONIC IMAGING OF THE NONLINEAR PARAMETERS B/A

这个应用程序的长期目标是开发一个 用于非线性成像的实时超声系统样机 参数B/A用于研究目的。非线性参数 B/A是衡量介质、支持 超声波相对于机械应变是非线性的。 对施加的机械应力作出反应而产生的。B/A 参数反映了在很大程度上没有观察到的介质的属性 通过其他成像方法，即，它似乎对 组织的结构层次结构的变化和对 大分子含量。因此，病理情况涉及 组织结构改变与大分子改变 重量成分提供的图像可以与 那些正常状态和不同的其他成像图式。 反射探头之间的非线性声学相互作用 信号和宽带泵浦波形在 相反方向，在探头中产生相变 在相互作用的空间区域，与B/A成正比。这个 沿接收到的探头的瞬时相变是 泵浦波形与空间分布的卷积 B/A沿交互路径。该调相探头可以 被处理以产生B/A的线条图像。多次反射 沿传播路径和需要泵浦波形 在广泛的波长范围内足够的能量是两个 研究中需要处理的问题。

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.