Li Jiayue, Pijewska Ewelina, Fang Qi, Szkulmowski Maciej, Kennedy Brendan F
BRITElab, Harry Perkins Institute of Medical Research, QEII Medical Centre Nedlands and Centre for Medical Research, The University of Western Australia, Crawley, Western Australia 6009, Australia.
Department of Electrical, Electronic & Computer Engineering, School of Engineering, The University of Western Australia, Crawley 6009, Australia.
Biomed Opt Express. 2022 Mar 18;13(4):2224-2246. doi: 10.1364/BOE.447340. eCollection 2022 Apr 1.
In compression optical coherence elastography (OCE), deformation is quantified as the local strain at each pixel in the OCT field-of-view. A range of strain estimation methods have been demonstrated, yet it is unclear which method provides the best performance. Here, we analyze the two most prevalent strain estimation methods used in phase-sensitive compression OCE, weighted least squares (WLS) and the vector method. We introduce a framework to compare strain imaging metrics, incorporating strain sensitivity, strain signal-to-noise ratio (SNR), strain resolution, and strain accuracy. In addition, we propose a new phase unwrapping algorithm in OCE, fast phase unwrapping (FPU), and combine it with WLS, termed WLS. Using the framework, we compare this new strain estimation method with both a current implementation of WLS that incorporates weighted phase unwrapping (WPU), termed WLS, and the vector method. Our analysis reveals that the three methods provide similar strain sensitivity, strain SNR, and strain resolution, but that WLS extends the dynamic range of accurate, measurable local strain, measuring a strain of 2.5 m with ∼4% error, that is ×11 and ×15 smaller than the error measured using WLS and the vector method, respectively. We also demonstrate, for the first time, the capability to detect sub-resolution contrast in compression OCE, , changes in strain occurring within the strain axial resolution, and how this contrast varies between the different strain estimation methods. Lastly, we compare the performance of the three strain estimation methods on mouse skeletal muscle and human breast tissue and demonstrate that WLS avoids strain imaging artifacts resulting from phase unwrapping errors in WLS and provides improved contrast over the other two methods.
在压缩光学相干弹性成像（OCE）中，变形被量化为OCT视场中每个像素处的局部应变。已经展示了一系列应变估计方法，但尚不清楚哪种方法性能最佳。在此，我们分析了相敏压缩OCE中使用的两种最普遍的应变估计方法，加权最小二乘法（WLS）和向量法。我们引入了一个框架来比较应变成像指标，包括应变灵敏度、应变信噪比（SNR）、应变分辨率和应变精度。此外，我们在OCE中提出了一种新的相位展开算法，快速相位展开（FPU），并将其与WLS相结合，称为WLS。使用该框架，我们将这种新的应变估计方法与结合加权相位展开（WPU）的当前WLS实现（称为WLS）以及向量法进行了比较。我们的分析表明，这三种方法提供了相似的应变灵敏度、应变SNR和应变分辨率，但WLS扩展了准确、可测量的局部应变的动态范围，测量的应变为2.5 m，误差约为4%，分别比使用WLS和向量法测量的误差小11倍和15倍。我们还首次展示了在压缩OCE中检测亚分辨率对比度的能力，即在应变轴向分辨率内发生的应变变化，以及这种对比度在不同应变估计方法之间如何变化。最后，我们比较了这三种应变估计方法在小鼠骨骼肌和人类乳腺组织上的性能，并证明WLS避免了由WLS中的相位展开误差导致的应变成像伪影，并且比其他两种方法提供了更好的对比度。
