Study of optical absorption and scattering of laser radiation by a biological tissue phantom using moveable integrating spheres
Tatiana K. Karpova,1 Nikita V. Kovalenko,1,2 Oleg A. Ryabushkin,1,2
1 Moscow Institute of Physics ans Technology (National Research University), Dolgoprudny, Russia
2 Fryazino Branch of the Kotelnikov Institute of Radioengineering and Electronics of Russian
Academy of Sciences, Fryazino, Russia
Abstract
In order to correctly describe the interaction of electromagnetic radiation with biological tissues, it is necessary to know the tissue’s optical properties. To measure optical properties of biological tissues and other turbid media, a new experimental method of moveable integrating spheres can be used [1]. In this method one needs to measure the dependencies of radiation fractions, diffusely reflected and transmitted by the sample and registered by the integrating spheres, on the distances between the sample surface and the ports of the corresponding spheres. This approach allows to determine the optical properties of turbid media more accurately as compared to the classical method, where measurements are conducted only with spheres located close to the sample surface. In this work we present the results of measuring absorption and scattering coefficients and scattering anisotropy of a biological tissue phantom using moveable integrating spheres. The phantom was made of epoxy resin with added aluminum oxide powder (scatterer) and india ink (absorber); the albedo of the sample was approximately 0.9, the scattering anisotropy was 0.85, and the thickness ranged from 1 to 5 mm. During the experiment, a multimode laser radiation of 589 nm wavelength and 1 mW power was normally incident on the sample surface; the diameter of the laser spot was adjusted by an aperture and equalled 1 mm. Radiation that was scattered from the sample in forward and backward directions was measured using integrating spheres with two ports; a photodetector was used to determine the fraction of unscattered radiation. The experimental results were analyzed using an inverse multilayer Monte Carlo algorithm adapted to describe the geometry of the experiment. The obtained values of the optical parameters of the phantom are in compliance with the values calculated according to the Mie scattering theory for the case of spherical particles in a transparent medium.
[1] Kovalenko N V et al 2019 Optical properties of biological tissues evaluation with a hybrid goniometer and integrating-sphere technique and Monte Carlo mathematical modelling J. Phys.: Conf. Ser. 1391 012025
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Tatiana Karpova
Moscow Institute of Physics ans Technology (National Research University)
Russia
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