oxygenation of blood and the brain, solution of problems of photoplethysmography, and diagnostics of cancerous tumors of stomach in vivo, etc. [1-3 ]. However, a variety of aspects associated with the use of these instruments need further study. In this work we investigated the possibility of the use of fiber-optical facilities for noninvasive identification of biological tissues of various kinds through layers of skin and muscles. Using this technique, it is possible to investigate layers of liver, lung, bone tissue, etc. in vitro. In simplified form the medium investigated consists of multilayer systems that model the actual position of the liver and the lung in the intercostal region on the right the chest. Therefore, we pose the problem of determining the coefficients of brightness of radiation reflected from multilayer systems in the visible and near IR regions of the spectrum, where biological tissues exhibit the greatest transparency [4-5 ]. The model experiment was staged as follows. Layers of skin with muscle tissue of a rabbit 10 and 20 mm thick were placed in glass cuvettes of thickness l = 10-30 mm, with layers of liver, lung, and bone tissue placed behind. For developing the technique of measurements we used layers of homogeneous tissues. Lasers with the wavelengths 2 -- 0.63, 0.83, and 1.15/~m were used as radiation The fiber-optical device (FOD) consists of transmitting fibers joined with the source and receiving fibers joined with the detector; the measuring end of the device contains both accepting and transmitting fibers. The appropriateness of the investigated FOD for spectroscopic investigations was appraised on the basis of the correspondence of the brightness coefficient of diffusely reflected radiation p, measured by this device, to the coefficient of diffuse reflection measured by an SFD-2 spectrophotometer equipped with a photometric sphere [6 ] when the depth mode [7 ] was realized in a layer of disperse material, which is the usual case for biological tissues of thickness l >- 0.5 cm. To reduce to a minimum the specular reflected radiation from the cuvette when using the FOD and thus to approximate as closely as possible the conditions of operation with a photometric sphere from which the specularly reflected radiation is taken out, we placed immersion liquid between the measuring end of the FOD and the cuvette surface. It should also be noted that in this case the values of Pi measured at the outlet from the cuvette with the immersion liquid coincide with similar data of P0 when the FOD is inserted directly into blood. Without immersion the values ofp differed from those of p0 by 10%. The data of p0 and R measured by means of the FOD and a photometric sphere (2 -- 0.63/~m) are presented in Table 1, which demonstrates their satisfactory agreement. The error of measurements did not exceed 5% when R _> 10%. Table 2 contains results of measurements for samples of multilayer systems. They demonstrate different contributions of radiation reflected from bone tissue, lung, and liver at a depth of l = 10 mm under a layer of skin and homogeneous muscle tissue to the brightness coefficients; at l -- 20 mm this identification is of low likelihood.
Search from 250 M+ research papersSearch from 250 M+ research papers
Dec 16, 2023
Ilhem Soyeh + 2
Open Access