Methodology for examining polarized light interactions with tissues and tissuelike media in the exact backscattering direction

Abstract

The properties of polarized light emerging from turbid media in the exact backscattering direction are studied by modulating the incident light polarization state and isolating the synchronous signal with lock-in amplifier detection. The results are reported for polystyrene microsphere suspensions in distilled water, with and without glucose, and for both ex vivo and in vivo biological tissues. A new theoretical formulation based on Mueller calculus is developed to describe the observed behavior of the backscattered light in terms of two sample parameters: optical rotation and depolarization. This technique proved successful in modeling both phantom and tissue samples. Results showed the presence of a significant surviving polarization fraction in the backscattering direction even in extremely dense optical phantom media, an important finding that has not been observed at other detection angles. Substantial polarized light preservation in biological tissue samples is also demonstrated for this detection geometry. This illustrates the potential of using polarized light to investigate turbid biological materials in vivo in retroreflection geometry.

Monte Carlo model and single-scattering approximation of the propagation of polarized light in turbid media containing glucose

“…23 Studinski and Vitkin studied the correlation between concentrations of chiral molecules in turbid media and the properties of polarized light emerging from turbid media, such as the optical rotation of the linearly polarized fractions and the degrees of polarization. 24 As a chiral material, glucose has preferential handedness because it has an asymmetric molecular structure. As a result, glucose interacts differently with right and left circularly polarized light, resulting in rotation of the linear polarization plane.…”

Stokes polarimetry imaging of rat‐tail tissue in a turbid medium using incident circularly polarized light

“…Tissue regions corresponding to Table 1B,C,D appeared to remit light with higher DoCP. The DoCP in these deeper embedded Table 1B,C,D regions is higher in two senses: (1) it is higher than the DoCP in the shallowly embedded rat tail; (2) it is higher than the DoCP in the Table 1A regions.…”

“…The polarization of light can survive through multiple scattering events in tissue and tissue phantoms [1,2]. The state of polarization can be measured using polarimetry techniques and can be used as a criterion for tissue-type distinction.…”

Effects of detection geometry on polarimetric measurements of scattered light from turbid media containing optically active glucose molecules

“…Optical methods are potentially well suited to tackle this problem due to their non-invasive and non-harmful nature and sensitivity to glucose induced optical changes 2-10 . Recently, polarized light has been used to sense the glucose level in optically thick tissues through the effects of blood glucose on the scattering properties of tissue [7][8][9] , which dominates optics of skin in the tissue optical window range of 600-1200 nm. Some research has examined the detection of scattered light in directions other than forward direction [11][12][13] , in search of optimal detection geometry where the experimental observables such as optical rotation, degree of polarization respond most to the increase of glucose concentration. The effort was challenged by the complexity of light-media interactions and experimental difficulties [12][13][14][15] .…”

“…Some research has examined the detection of scattered light in directions other than forward direction [11][12][13] , in search of optimal detection geometry where the experimental observables such as optical rotation, degree of polarization respond most to the increase of glucose concentration. The effort was challenged by the complexity of light-media interactions and experimental difficulties [12][13][14][15] .…”