Evaluating Tissue Mechanical Properties Using Quantitative Mueller Matrix Polarimetry and Neural Network

Abstract

Evaluation of the mechanical properties of biological tissues has always been an important issue in the field of biomedicine. The traditional method for mechanical properties measurement is to perform in vitro tissue deformation experiments. With the fast development of optical and image processing techniques, more and more non-invasive and non-contact optical methods have been applied to the analysis of tissue mechanical features. In this study, we use Mueller matrix polarimetry to quantitatively obtain the mechanical properties of bovine tendon tissues. Firstly, to study the structural information and the changes in the optical characteristics of the tendon tissue under different stretching states, 3 × 3 Mueller matrix images of bovine tendon tissue samples are acquired by backscattering measurement setups based on a polarized camera. Then, we extract the frequency distribution histograms (FDHs) of the Mueller matrix elements to reveal the structural changes of the tendon tissue more clearly during the stretching process. Last, we calculate the Mueller matrix transformation (MMT) parameters, the total anisotropy and the anisotropy direction of the tendon tissue samples under different stretching processes to quantitatively characterize their structural changes under different mechanical states. The central moments of the MMT parameters can be used to distinguish the different stretching states of the tendon tissue. For better discrimination based on the MMT parameters, we design a multilayer neural network that takes the first-order moments of the MMT parameters as the input features. After training, a high-precision classification model of the stretching states of tendon tissue samples is finally obtained, and the total classification accuracy achieves 98%. The experimental results show that the Mueller matrix polarimetry can be a potential non-contact tool for tissue mechanical properties evaluation.

Evaluating tissue mechanical properties using Mueller matrix polarimetry

“…In previous study, the 4×4 Mueller matrix is commonly used as it contains full polarization information. However, the 3×3 Mueller matrix contains much of the structural information of bulk tendon tissues so that we can spend less time measuring the Mueller matrix [34]. And we can calculate the 3×3 Mueller matrix using Equation (1):…”

“…The first parameter t1 characterizes the total anisotropy, and the second parameter α1 represents the anisotropic orientation [35,36]. By analyzing the MMT parameters t1 and α1, we can potentially detect external forces applied to the sample at various angles [34].…”

“…By calculating the Mueller matrix of the sample, we can extract some parameters used to characterize the optical properties of the sample, such as linear dichroism, linear depolarization ability, anisotropy [6,34,41], etc. As shown in Figure 2(a), for a sample, we obtained 4 Mueller matrix images in different stretching states.…”

Automatic detection and quantitative evaluation of skin hair follicles based on Mueller matrix polarimetry

“…Recently, Mueller matrix polarimetry has attracted more and more attention in the field of biophotonics, because it can detect abundant microstructural and optical properties of biomedical samples non-invasively and label-freely [7][8][9][10][11][12] . Moreover, Mueller matrix polarimetry has excellent compatibility with commercial optical imaging systems such as microscopes and endoscopes 13 .…”

Analyzing the influence of imaging resolution on tissue polarimetry basis parameters

“…For example, they can be used to identify the location and number of hair follicles 11 , and polarization virtual staining with MMPD parameters can distinguish different collagen fibers 12 . MMT parameters have shown promising applications in biomechanics 13 , and some polarization parameters are sensitive to multi-layer information [14][15][16][17] . In addition, polarization parameters have shown great capability in cancer diagnosis, such as cervical cancer 18,19 , breast cancer 20 , and basal cell skin cancer 21,22 .…”