Abstract
Biomedical photometersʼ information-measuring systems with ellipsoidal reflectors have acceptable results in determining of biological tissues optical properties in the visible and near-infrared spectral range. These photometers make it possible to study the optical radiation propagation in turbid media for direct and inverse problems of light-scattering optics. The purpose of this work is to study the influence of the ellipsoidal reflectors design parameters on the results of biomedical photometry when simulating the optical radiation propagation in a system of biological tissue and reflectors in transmitted and reflected light.The paper substantiates the choice of the ellipsoidal reflectors’ focal parameter for efficient registration of forward and backscattered light. The methodology of the process is illustrated by the results of a model experiment using the Monte Carlo simulation for samples of human brain white and gray matter at the visible range of 405 nm, 532 nm, and 650 nm. The total transmittance, diffuse reflectance, and absorption graphs depending on the sample thickness were obtained. Based on the introduced concepts of the ellipsoidal reflector efficiency index and its efficiency factor, the expediency of choosing the ellipsoidal reflectors focal parameter is analyzed to ensure the registration of the maximum amount of scattered light. The graphs of efficiency index in reflected and transmitted light for different thickness samples of white and gray matter and efficiency factors depending on the sample thickness were obtained.The influence of the reflectors ellipticity on the illuminance of various zones of photometric images using the example of an absorbing biological medium – pig liver tissue – at wavelength of 405 nm with a Monte Carlo simulation was analyzed.The optical properties of biological media (scattering and absorption coefficients, scattering anisotropy factor, refractive index) and the samples’ geometric dimensions, particularly the thickness, are predetermined when choosing the ellipsoidal reflectors parameters for registration of the scattered light. Coordinates of the output of photons and their statistical weight obtained in the Monte Carlo simulation of light propagation in biological tissue have a physical effect on a characteristic scattering spot formation in the receiving plane of a biomedical photometer with ellipsoidal reflectors.
Highlights
IntroductionBiomedical photometers (separate devices) and photometric systems (composite modules of diagnostic complexes) use the entire range of optical systems, the converting properties of which have been adequately described and studied
Biomedical photometers and photometric systems use the entire range of optical systems, the converting properties of which have been adequately described and studied
Such features and requirements for the information content of photometry predetermine the need to increase the amount of registered light, which is achieved by selecting contactless measurement methods and optical systems with a wide aperture, or by using contact measurements with optical elements of the atypical configuration
Summary
Biomedical photometers (separate devices) and photometric systems (composite modules of diagnostic complexes) use the entire range of optical systems, the converting properties of which have been adequately described and studied. It should be noted that depending on the incident light parameters (for this class of devices, as a rule, laser), the received luminous flux contains components that characterize the surface topography, a boundary separating two media, and scattering properties in a quasi-homogeneous layer. Such features and requirements for the information content of photometry predetermine the need to increase the amount of registered light, which is achieved by selecting contactless measurement methods and optical systems with a wide aperture, or by using contact measurements with optical elements of the atypical configuration. The purpose of this work is to study the influence of the ellipsoidal reflectors design parameters on the results of biomedical photometry when simulating the optical radiation propagation in a system of biological tissue and reflectors in transmitted and reflected light
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