Univ. of Washington, United States.
J Biomed Opt. 2019 Jul;24(7):1-11. doi: 10.1117/1.JBO.24.7.076003.
Dynamic elastography is an attractive method to evaluate tissue biomechanical properties. Recently, it was extended from US- and MR-based modalities to optical ones, such as optical coherence tomography for three-dimensional (3-D) imaging of propagating mechanical waves in subsurface regions of soft tissues, such as the eye. The measured group velocity is often used to convert wave speed maps into 3-D images of the elastic modulus distribution based on the assumption of bulk shear waves. However, the specific geometry of OCE measurements in bounded materials such as the cornea and skin calls into question elasticity reconstruction assuming a simple relationship between group velocity and shear modulus. We show that in layered media the bulk shear wave assumption results in highly underestimated shear modulus reconstructions and significant structural artifacts in modulus images. We urge the OCE community to be careful in using the group velocity to evaluate tissue elasticity and to focus on developing robust reconstruction methods to accurately reconstruct images of the shear elastic modulus in bounded media.
动态弹性成像是评估组织生物力学特性的一种很有吸引力的方法。最近，它已经从基于 US 和 MR 的模式扩展到光学模式，例如光学相干断层扫描（OCT），用于对眼等软组织的亚表面区域传播的机械波进行三维成像。所测量的群速度通常用于根据体剪切波的假设，将波速图转换为弹性模量分布的三维图像。然而，在角膜和皮肤等有界材料中的 OCE 测量的具体几何形状使得在假设群速度和剪切模量之间存在简单关系的情况下进行弹性重建受到质疑。我们表明，在层状介质中，体剪切波的假设导致剪切模量重建被严重低估，并且在模量图像中出现明显的结构伪影。我们敦促 OCE 界在使用群速度评估组织弹性时要小心，并专注于开发稳健的重建方法，以准确重建有界介质中剪切弹性模量的图像。
