Dept. d'Inf. et de Recherche Oper., Montreal Univ., Que.
IEEE Trans Med Imaging. 1995;14(2):293-300. doi: 10.1109/42.387711.
A theoretical model was previously developed to evaluate the relationship between the dynamics of ultrasonic speckle and its underlying tissue. The model is divided into an instrumental part represented by the point spread function (in the far field) of the ultrasonic apparatus and a moving tissue component described by a collection of scatterers. By computing the convolution of these terms and then the envelope, one obtains a simulated ultrasonic speckle pattern sequence which shows speckle motions closely linked to the tissue dynamics when small motion amplitudes are involved. Here, a theoretical study of the correlation between various linear transformations of the tissue and the corresponding ultrasonic speckle motions is performed, based on a 2D extension of the envelope cross-correlation analysis of a narrow-band Gaussian noise. In the linear scan case, obviously, tissue translation generates an identical speckle translation. However, tissue/speckle motion correlation decreases with increasing rotation and/or biaxial deformation, lateral deformation (perpendicular to the beam propagation axis) being much less sensitive. With respect to the transducer frequency, the rotation and the axial deformation of the tissue show a better relationship with their respective speckle motion at lower frequencies while lateral deformation correlation is independent of the pulse frequency. With respect to beam (pulse) size parameters, tissue/speckle correlation decreases with rotation when a wide ultrasonic beam is used while the axial deformation correlation decreases with the axial duration of the pulse. This study sets the ground for the development of an ultrasonic strain gauge particularly useful for the assessment of biomechanical soft tissue and fluid flow properties based on speckle tracking.
先前已经建立了一个理论模型，用于评估超声散斑的动力学与其潜在组织之间的关系。该模型分为两个部分，分别由超声设备的点扩散函数（远场）和一组散射体描述的运动组织部分表示。通过计算这些项的卷积，然后计算包络，就可以获得模拟的超声散斑模式序列，当涉及小运动幅度时，该序列显示与组织动力学紧密相关的散斑运动。在此，基于对窄带高斯噪声的包络互相关分析的二维扩展，对组织的各种线性变换与相应的超声散斑运动之间的相关性进行了理论研究。在线性扫描情况下，显然，组织平移会产生相同的散斑平移。但是，随着旋转和/或双轴变形的增加，组织/散斑运动相关性会降低，侧向变形（垂直于光束传播轴）的敏感性较低。关于换能器频率，在较低频率下，组织的旋转和轴向变形与其各自的散斑运动具有更好的相关性，而侧向变形相关性与脉冲频率无关。关于光束（脉冲）尺寸参数，当使用宽超声束时，组织/散斑相关性随着旋转而降低，而轴向变形相关性随着脉冲的轴向持续时间而降低。这项研究为超声应变计的开发奠定了基础，这种应变计特别适用于基于散斑跟踪评估生物力学软组织和流体流动特性。
