The paper presents a new method for distant non-destructive determination of concentration of light absorbing admixtures in turbid media. In particular, it is intended for non-invasive in vivo control of accumulation in patient tissues of various biochemicals introduced to the patients for chemotherapy, photodynamic therapy or diagnostics. It is require that the admixture absorption spectrum should have a clearly marked peak in the wavelength region where the pure medium one varies regularly. Fluorescence of admixtures is not required. The method uses the local diffuse reflectance spectroscopy with optical fiber probe including one emitting and two reading There are several features in the method: the value to be determined is absolute concentration of admixtures; the method needs no calibration measurements on phantoms; it needs no reference measurements on sample with zero admixture concentration; it uses a two parametric kinetic light propagation model and original algorithms to resolve direct and inverse tasks of radiation transport theory. Experimental testing passed with tissue equivalent phantoms and different admixtures, including a chlorine photosensitizer, showed accuracy under 10% in all cases.
A method for non-destructive determination of absorption and transport (reduced) scattering coefficients of turbid media
(biological tissue, first of all) is presented. It refers to the spatially resolved diffuse reflectance techniques with optical
fiber probe. The method is based on a more accurate (in comparison with diffusion) two parameters kinetic light
propagation model and a special two step non-analog Monte Carlo technique, it involves no additional parameters and
uses no assumptions about spectral dependencies of the coefficients, allows application of monochrome sources and
probes with minimally possible number of reading fibers (only 2), goes without calibration phantoms and measurements.
Numerical and experimental testing have showed the measured coefficients provide a good prediction of both light
reflection and penetration fields in semi-infinite homogeneous media with low-mid absorption.
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