Lagrangian speckle model and tissue-motion estimation - Theory
Lagrangian speckle model and tissue-motion estimation - Theory
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DOI：
10.1109/42.790459
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发表时间：
1999-07-01
影响因子：
10.6
通讯作者：
Bertrand, R
中科院分区：
文献类型：
--
作者：
Maurice, RL;Bertrand, R
众所周知，当组织受到诸如旋转、剪切、缩放等运动时，由此产生的斑点模式的变化充当噪声源，通常负责大部分位移估计方差。从建模的角度来看，这些变化可以被认为是由两种机制引起的：一种是斑点的运动，另一种是它们形态的改变。在本文中，我们提出了一种新的组织运动估计器来抵消这些散斑去相关效应。估计是基于散斑运动的拉格朗日描述。这种描述使我们能够遵循散斑场的局部特征，就好像它们是一种材料属性一样。该方法以一种能够推导出用于散斑恢复的适当逆滤波器的方式，导致对去相关的解析描述。该滤波器适用于散射函数（LT）的线性几何变换，即恒定应变感兴趣区域（ROI）。由于LT本身是滤波器的一个参数，因此组织运动估计器可以被表述为一个非线性最小化问题，寻求组织运动前图像和恢复散斑后图像之间的最佳匹配。该方法进行了测试，使用模拟射频（RF）图像的组织进行轴向剪切。
It is known that when a tissue is subjected to movements such as rotation, shearing, scaling, etc., changes in speckle patterns that result act as a noise source, often responsible for most of the displacement-estimate variance. From a modeling point of view, these changes can be thought of as resulting from two mechanisms: one is the motion of the speckles and the other, the alterations of their morphology. In this paper, we propose a new tissue-motion estimator to counteract these speckle decorrelation effects. The estimator is based on a Lagrangian description of the speckle motion. This description allows us to follow local characteristics of the speckle field as if they were a material property. This method leads to an analytical description of the decorrelation in a way which enables the derivation of an appropriate inverse filter for speckle restoration. The filter is appropriate for linear geometrical transformation of the scattering function (LT), i.e., a constant-strain region of interest (ROI). As the LT itself is a parameter of the filter, a tissue-motion estimator can be formulated as a nonlinear minimization problem, seeking the best match between the pre-tissue-motion image and a restored-speckle post-motion image. The method is tested, using simulated radio-frequency (RF) images of tissue undergoing axial shear.