Size-dependent patterns in depolarization maps from turbid medium and tissue

Abstract

Mueller matrix measurements on turbid media can be used to quantify its polarization properties in terms of retardance, diattenuation, and depolarization. In particular, the depolarizing ability of such media, which is represented by the depolarization index, has been shown to be a useful diagnostic parameter. However, being a single valued metric, its dependence on a host of tissue optical parameters makes it difficult to interpret. In this paper, we show that a map of depolarization as a function of input polarization state parameters can be used to infer information about the size of scatterer and order of birefringent and depolarizing layers in turbid medium. The experiments carried out on different mice organ tissues indicate that the depolarization characteristics of tissue are closely represented by depolarization properties of intralipid. We also observed that these maps do not vary in the presence of absorption.

Enhanced contrast and depth resolution in polarization imaging using elliptically polarized light

“…Note that some recent studies have demonstrated that circularly polarized light is more depolarized in Intralipid ®25 and tissue samples 26 than linearly polarized light. The depolarization factor, that is the ratio between the intensity of detected polarized light to intensity of illuminated polarized light, has not been considered for our studies and only the signal containing polarization maintaining volume is taken into consideration.…”

Polarized light interaction with tissues

“…However, for thick turbid tissues where polarization alteration can be due to multiple scattering effects, Mueller matrix measurements should be processed by its polar decomposition to quantify diattenuation, retardance, and depolarization separately. [18][19][20][21][22]105,[194][195][196] Following a paper by Gupta et al, 105 it is possible to underline some typical overlapping polarization effects that can be detected in multiple scattering tissues. A rotation of the plane of polarization of incident linearly polarized light (retardance) can be caused both by the presence of chiral molecules such as glucose or due to the diattenuation and retardance caused by single backscattering.…”

“…15,103 However, more often, Stokes or Mueller polarimeters based on intensity measurements of polarized light are used. 5,15,21,22,[30][31][32][33][34][35][36][37][38]87,91,92,[96][97][98][99][100][101][104][105][106][107][108] In that case, light of an arbitrary polarization can be represented by four numbers known as the Stokes parameters, I; Q; U, and V (I 2 ¼ Q 2 þ U 2 þ V 2 ), where I refers to the intensity of the light, and the parameters Q; U, and V represent the extent of the horizontal linear, 45 deg linear, and circular polarization, respectively. 22,30,96,107 In polarimetry, the Stokes vector S of a light beam is constructed based on six flux measurements obtained with different polarization analyzers in front of the detector, From the Stokes vector, the degree of polarization (P), degree of linear polarization (P L ), and the degree of circular polarization (P C ) are derived as 5,15,22,34 E Q -T A R G E T ; t e m p : i n t r a l i n k -; e 0 0 3 ; 3 2 6 ; 3 6 9 P ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ffi…”

“…In terms of the Stokes vector and Mueller matrix (LSM) elements, these basic parameters can be expressed as follows. If the degree of polarization P of a light field remains at unity after transformation by an optical system, this system is nondepolarizing; otherwise, the system is depolarizing, with the depolarization being a function of input polarization, 105,106 E Q -T A R G E T ; t e m p : i n t r a l i n k -; e 0 1 4 ; 3 2 6 ; 2 6 3…”

“…In addition to the abovediscussed scattering angular-resolved Mueller matrix measurements, its spatially and spectrally resolved studies can provide valuable information for successful deconvolution of some of the different contributions. 105,145 Polar decomposition of the Mueller matrix [18][19][20][21][22]105,[194][195][196] is an efficient way to quantify tissue polarization properties from the measured Mueller matrix, which is presented as a combination of a diattenuator M D , a retarder M R , and a depolarizer M Δ matrices. The steps involved in the polar decomposition of the Mueller matrix are shown as a flowchart in Fig.…”