Zvietcovich Fernando, Ge Gary R, Mestre Humberto, Giannetto Michael, Nedergaard Maiken, Rolland Jannick P, Parker Kevin J
Dept. of Electrical & Computer Engineering, University of Rochester, Rochester, NY 14627, USA.
The Institute of Optics, University of Rochester, Rochester, NY 14627, USA.
Biomed Opt Express. 2019 Jul 1;10(7):3699-3718. doi: 10.1364/BOE.10.003699.
In dynamic optical coherence elastography (OCE), surface acoustic waves are the predominant perturbations. They constrain the quantification of elastic modulus to the direction of wave propagation only along the surface of tissues, and disregard elasticity gradients along depth. Longitudinal shear waves (LSW), on the other hand, can be generated at the surface of the tissue and propagate through depth with desirable properties for OCE: (1) LSW travel at the shear wave speed and can discriminate elasticity gradients along depth, and (2) the displacement of LSW is longitudinally polarized along the direction of propagation; therefore, it can be measured by a phase-sensitive optical coherence tomography system. In this study, we explore the capabilities of LSW generated by a circular glass plate in contact with a sample using numerical simulations and tissue-mimicking phantom experiments. Results demonstrate the potential of LSW in detecting an elasticity gradient along axial and lateral directions simultaneously. Finally, LSW are used for the elastography of mouse brain and demonstrate important implications in and measurements of local elasticity changes in brain and how they might correlate with the onset and progression of degenerative brain diseases.
在动态光学相干弹性成像（OCE）中，表面声波是主要的扰动因素。它们将弹性模量的量化限制在仅沿组织表面的波传播方向上，而忽略了沿深度方向的弹性梯度。另一方面，纵向剪切波（LSW）可以在组织表面产生，并以适合OCE的特性在深度方向传播：（1）LSW以剪切波速度传播，能够区分沿深度方向的弹性梯度；（2）LSW的位移沿传播方向纵向极化，因此可以通过相敏光学相干断层扫描系统进行测量。在本研究中，我们通过数值模拟和组织模拟体模实验，探索了与样品接触的圆形玻璃板产生的LSW的能力。结果证明了LSW在同时检测轴向和横向弹性梯度方面的潜力。最后，LSW被用于小鼠脑的弹性成像，并在测量脑内局部弹性变化以及这些变化与退行性脑疾病的发生和发展之间的关联方面显示出重要意义。
