In vivo endoscopic tissue diagnostics based on spectroscopic absorption, scattering, and phase function properties

Abstract

A fast spectroscopic system for superficial and local determination of the absorption and scattering properties of tissue (480 to 950 nm) is described. The probe can be used in the working channel of an endoscope. The scattering properties include the reduced scattering coefficient and a parameter of the phase function called gamma, which depends on its first two moments. The inverse problem algorithm is based on the fit of absolute reflectance measurements to cubic B-spline functions derived from the interpolation of a set of Monte Carlo simulations. The algorithm's robustness was tested with simulations altered with various amounts of noise. The method was also assessed on tissue phantoms of known optical properties. Finally, clinical measurements performed endoscopically in vivo in the stomach of human subjects are presented. The absorption and scattering properties were found to be significantly different in the antrum and in the fundus and are correlated with histopathologic observations. The method and the instrument show promise for noninvasive tissue diagnostics of various epithelia.

Quantification of the optical properties of two-layered turbid media by simultaneously analyzing the spectral and spatial information of steady-state diffuse reflectance spectroscopy

“…Therefore, we focus on steady-state DRS techniques in this paper. By measuring and analyzing diffuse reflectance at multiple source-detector separations (SDS) which is known as spatially-resolved diffuse reflectance, reasonably high accuracies of quantifying the optical properties of homogeneous tissue mimicking phantoms have been demonstrated [9, [13][14][15][18][19][20][21]. Spatially-resolved steady-state DRS systems can be equipped with a broadband light source and a spectral detection device to achieve fast acquisition of full spectra and more robust identification and quantification of multiple chromophores present in the tissue [13,14,18,19].…”

“…Examples of forward models include analytical models using the diffusion approximation to solve the radiative transport equation [8][9][10][11][12][13][14], numerical models based on Monte Carlo (MC) simulations [15][16][17][18][19][20] and empirical models [5,21]. Instruments used to measure diffuse reflectance for the quantification of tissue optical properties can be categorized into time-resolved [22], frequency-domain [23] and steady-state methods [5,[8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Time-resolved and frequency-domain approaches are limited to near-infrared wavelengths with relatively large penetration depths (>2 mm) and are not be suitable for detecting optical properties of epithelium and superficial stroma where epithelial precancer and early cancer reside.…”

Lookup table-based sampling of the phase function for Monte Carlo simulations of light propagation in turbid media

“…The anisotropy factor g can be found to be as low as 0.4 [24] and can reach values of up to 0.98 [25] in the biological tissues. With respect to parameter γ, the values tend to lie between 1.1 and 2.3 [6,26,27]. As a result, we have utilized 15 phase functions listed in Table 1.…”

Development of thin skin mimicking bilayer solid tissue phantoms for optical spectroscopic studies

“…Extensive studies have been conducted in this direction for distinguishing normal and cancerous tissues in various organs such as human lungs, breast, colon, cervix, head etc [5][6][7][8]. In general, biological tissues are inhomogeneous structures, composed of complex milieu of several absorbers, scatterers and fluorophores that are present in different concentration at different depths [9,10]. In such a turbid medium, intrinsic fluorescence extraction of individual fluorophores is hindered by the complex interplay of several factors like absorption and scattering from non-fluorescing agents within different sub layers of tissue [11].…”