ABSTRACT
Optical polarimetry have been extensively used for the non-invasive assessment of biological tissues. However, the knowledge regarding differences in polarimetric signatures of different tissue pathologies is very scattered, confounding the deduction of a global trend of the polarimetric variables for healthy and pathological tissues. The purpose of this study was to bridge this gap. We conducted a rigorous online survey to collect all published studies that report the two most common polarimetric variables (i.e., depolarization and retardance) for any type of tissue pathology. A total of 101 studies describing the polarimetric assessment of tissues were collected, wherein 253 (i.e., nhuman = 149, nanimal = 104) different type of tissues were optically characterized. Most tissue samples (172/253) were investigated in ex vivo settings. The data showed 32 different types of tissues pathologies, where the most common pathology was cancer and its subtypes. The skin tissues were the most frequently explored tissues, followed by tissue samples from breast, colon, liver, and cervix. Although differences in polarimetric signatures of different tissue pathologies were summarized from the included studies, generalization of the results was hindered by the presentation of polarimetric data in a non-uniform format. The analyses presented in this study may provide an important reference for future polarimetric studies that conduct optical assessment of tissues at greater depth, particularly in the context of optical biopsy/digital staining.
Subject(s)
Breast , Skin , Animals , Liver , Spectrum AnalysisABSTRACT
The prevailing formalisms for isolating individual polarization effects from the experimental Mueller matrix M can be broadly divided into two categories; decomposition of M to derive the individual optical effects and directly associating the individual optical effects to specific elements of M (i.e., non-decomposition techniques). Mueller matrix transformation (MMT) and direct interpretation of Mueller matrix (DIMM) are two popular techniques of the latter category. In this study, these two non-decomposition techniques (i.e., MMT and DIMM) are compared in a detailed quantitative analysis comprising of tissues (n = 53) and phantom (n = 45) samples. In particular, two commonly investigated polarimetric variables (i.e., depolarization and retardance) were calculated from the experimentally measured M using both the non-decomposition (i.e., MMT and DIMM) techniques. The comparison carried out with scatter plots (integrated with the correlation coefficients), violin plots and Bland and Altman plots revealed better agreement of depolarization-related variables (as compared to the retardance) between the two non-decomposition techniques. The comparative analyses presented here would be beneficial for the interpretation of polarimetric variables and optical characterization of turbid media.
ABSTRACT
Mueller matrix polarimetry (MMP) has emerged as a simple, fast and non-invasive optical tool in basic and preclinical research whereby polarized light measurements are used to characterize biological samples. The skin tissue being exposed can be easily sampled, and the highly anisotropic nature of its ultra-structural components (e.g., the dense collagen/ elastin matrix, fibers) enable it a particularly suitable site for MMP investigations. In this study, we aim to survey, summarize, analyze and speculate on the trends in the literature which deals with the MMP of skin tissues. Specifically, we start with a brief description of the experimental implementation of MMP technique, with a focus on both the hardware and methodology, followed by a comprehensive online literature survey to summarize the MMP data pertaining to skin tissues and associated pathologies. Finally, the polarimetric data of skin tissues have been analyzed, quantitatively compared (using box and whisker plot and student t test) and the observed trends interpreted with the help of tissue morphology. We expect that this work will provide a useful reference to a comprehensive MMP analysis of the skin tissues.
