Nonlinear elasticity imaging: Theory and phantom study
Nonlinear elasticity imaging: Theory and phantom study
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DOI：
10.1109/tuffc.2004.1320826
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发表时间：
2004-05-01
影响因子：
3.6
通讯作者：
O'Donnell, M
中科院分区：
文献类型：
--
作者：
Erkamp, RQ;Emelianov, SY;O'Donnell, M
在组织中，不能假定杨氏模数在较大的变形范围内保持不变。例如，对人体前列腺的直接机械测量显示，在10%的变形中，杨氏模数增加了三倍。在传统的弹性成像中，这些效应产生与应变相关的弹性对比度。忽略这些影响通常会导致次优对比度(低应变下的僵硬组织与高应变下的软组织形成对比)，但测量非线性行为会导致组织分化的增强。为了验证提取非线性弹性属性的方法，在琼脂-明胶模型上进行了模拟和测量。当体模变形12%时，采集了多帧相敏超声数据。所有帧间位移数据将返回到第一帧的几何体，以形成三维(3-D)数据集(深度、侧向和预载荷维)。数据被照亮到每个像素的3-D二次多项式模型，该模型调整变形不规则性。对于本文所考虑的体模几何和弹性性质，使用该模型重建的帧到帧的应变图像在不影响空间分辨率的情况下，在所有预载荷水平下都能改善对比噪声比(CNR)。从同一模型中，可以提取所有预载荷级的应变硬化。这是一个独立的对比机制。它的最大压缩比出现在5.13%的预加载，比最好的帧到帧应变重建的压缩比(预加载10.6%)提高了54%。实际体模测量证实了模拟的基本特征。结果表明，对非线性弹性行为的建模既有可能提高弹性成像的可检测性，又为组织分化提供了一种新的独立机制。
In tissue the Young's modulus cannot be assumed constant over a wide deformation range. For example, direct mechanical measurements on human prostate show up to a threefold increase in Young's modulus over a 10% deformation. In conventional elasticity imaging, these effects produce strain-dependent elastic contrast. Ignoring these effects generally leads to suboptimal contrast (stiffer tissues at lower strain are contrasted against softer tissues at higher strain), but measuring the nonlinear behavior results in enhanced tissue differentiation.To demonstrate the methods extracting nonlinear elastic properties, both simulations and measurements were performed on an agar-gelatin phantom. Multiple frames of phase-sensitive ultrasound data are acquired as the phantom is deformed by 12%. All interframe displacement data are brought back to the geometry of the first frame to form a three-dimensional (3-D) data set (depth, lateral, and preload dimensions). Data are lit to a 3-D second order polynomial model for each pixel that adjusts for deformation irregularities. For the phantom geometry and elastic properties considered in this paper, reconstructed frame-to-frame strain images using this model result in improved contrast to noise ratios (CNR) at all preload levels., without any sacrifice in spatial resolution. From the same model, strain hardening at all preload levels can be extracted. This is an independent contrast mechanism. Its maximum CNR occurs at 5.13% preload, and it is a 54% improvement over the best case (preload 10.6%) CNR for frame-to-frame strain reconstruction. Actual phantom measurements confirm the essential features of the simulation.Results show that modeling of the nonlinear elastic behavior has the potential to both increase detectability in elasticity imaging and provide a new independent mechanism for tissue differentiation.