Comparative study of polarized light propagation in biologic tissues

Abstract

We report the depolarization of light scattered by a variety of birefringent and nonbirefringent tissues. We used Stokes polarimetry to investigate how scatterer structures in each tissue contribute to the depolarization of linearly versus circularly polarized light propagating through that tissue. Experiments were performed on porcine blood, fat, tendon, artery, and myocardium. The results indicate that the two incident polarization states are depolarized differently depending on the structure of the sample. As seen in sphere suspensions, for tissues containing dilute Mie scatterers, circularly polarized light is maintained preferentially over linearly polarized light. For more dense tissues, however, the reverse is true. The results illustrate situations where polarized light will provide an improvement over unpolarized light imaging, information that is crucial to optimizing existing polarimetric imaging techniques.

Dichroism-sensitive photoacoustic computed tomography

“…The ultimate depth is where the light is depolarized due to scattering to the noise level [20,21]. To quantify the depolarizing effect based on pure optical measurements, we measured the speckle contrast after light passed through scattering media with different thicknesses.…”

Turbid medium polarimetry in biomedical imaging and diagnosis

“…An interesting feature that can be noted from equations (19) and (20) is that for a medium comprised of Rayleigh scatterers (a λ, g ∼ 0), depolarization of circularly polarized light should be stronger than linearly polarized light (ξ l > ξ c ). The reverse should be the case (ξ l < ξ c ) for media comprised of larger scatterers (a ≥ λ, g ≥ 0.7, Mie regime).…”

“…Suspension of Intralipid or aqueous suspension of polystyrene microspheres has usually been used to prepare tissue phantoms for polarimetric studies [18][19][20][21][22]. The usual approach has been to use a chosen size of scatterers that would give a value of anisotropy parameter (g) comparable to that of tissue.…”

“…Since it is difficult to quantify the morphological parameters of a complex system like tissue, in most of the experimental depolarization studies, the individual influence of these morphological parameters has been systematically investigated on well-characterized tissue simulating phantoms [6,[18][19][20][21][22]. Suspension of Intralipid or aqueous suspension of polystyrene microspheres has usually been used to prepare tissue phantoms for polarimetric studies [18][19][20][21][22].…”

“…These are supplemented by suitable theoretical treatments (based on radiative transport theory, diffusion theory and Monte Carlo techniques) for modeling polarized light propagation in random medium [10][11][12][13][14][15][16][17]. Numerous studies have also addressed depolarization studies on tissue simulating phantoms (whose constituent scattering and polarization properties are known and user-controlled a priori) to understand the polarization properties of multiply scattered light (and the mechanism of depolarization) in tissue for practical implementation of the polarization gating scheme for tissue imaging [18][19][20][21][22]. Note that for the realization of the polarimetric approaches for quantitative tissue diagnosis also, one needs to develop similar experimental turbid polarimetry systems, theoretical treatments for forward modeling of complex tissue polarimetry events, inverse analysis methods for extraction and quantification of the constituent intrinsic tissue polarimetry characteristics.…”