Tissue Self-Affinity and Polarized Light Scattering in the Born Approximation: A New Model for Precancer Detection

Abstract

Light scattered from biological tissues can exhibit an inverse power law spectral component. We develop a model based on the Born approximation and von Karman (self-affine) spatial correlation of submicron tissue refractive index to account for this. The model is applied to light scattering spectra obtained from excised esophagi of normal and carcinogen-treated rats. Power law exponents used to fit dysplastic tissue site spectra are significantly smaller than those from normal sites, indicating that changes in tissue self-affinity can serve as a potential biomarker for precancer.

Fourier spectrum analysis of full-field optical coherence tomography for tissue imaging

“…The spectral changes induced by the refractive index spatial correlation in tissue have also been theoretically analysed [9] and experimentally measured [29]. It was also found that modelling tissue structure in terms of refractive correlation function may provide new methods of diagnosing cancers [26]. And the power-law exponent of the backscattering spectrum is sensitive to the length scale at approximately 30-450 nm [36].…”

“…However, because of the existence of the spatial correlation of the refractive index of the medium, the spectrum of the scattered light in the far zone will be modified by a multiplicative factor that is proportional to the three-dimensional Fourier transform of the spatial correlation function of the random medium [29]. For tissue scattering, experimental data reveal that at the micrometre level [24] and submicrometre level [26,37,38], the spectrum of the scattered light is dominated by the fractal behaviour of tissue. Sheppard [23] also pointed out that the fractal tissue model may work best when one is concerned with details smaller than the typical size of organelles.…”

“…Several methods have been proposed to determine the form of the refractive correlation function [24,26,37,38]. The refractive correlation function can be directly derived from the microscopic images of slices of the tissue samples obtained with phase-contrast microscopy by fitting the measured spectral data to the von Karman spectral equation [24].…”

“…It was observed experimentally that there exist significant differences between the values of fractal dimension and fractal scale of the normal and dysplastic rat oesophagi [26]. The inverse power-law spectral dependence of the light scattered from submicrometre features in tissue samples was derived from the WhittleMatérn correlation function [27].…”

“…In fact, the angular distribution of the scattered light is determined by the Fourier transform of the spatial correlation function of the refractive index or dielectric permittivity which randomly fluctuates with position. And the possible range of the Fourier components that can be measured is determined by the range of both the wavelengths of the light sources and the angles of the observation [24][25][26][27][28][29][30][31][32][33].…”