[Research on the near-infrared (NIR) photon migration in multi-layered structures of biological tissues]

The phenomena of photon migration in multi-layered structures of biological tissue is very important in the field of non-invasive near-infrared optical diagnosis. In this paper, a two-layered structure consisting of the fat and the muscle of poke was used as the sample. Near-infrared light source and detector were located on the surface of the fat and a part of the photons reflected by the two-layered structure of the tissue were detected. The relationship between the optical current and the distance from source to detector and the relationship between the optical current and the thickness of the fat layer were given. In order to analyze the experiment results, Monte-Carlo simulation was used to calculate the photons migration traces in the uniform tissues and the Fresnel's law is used to determine the refraction and reflection components of a photon package at the boundary between the fat and the muscle. The results showed that the simulation data coincident well with the experimental results. The conclusion is that the experiment and the simulation method provided in this study may be useful to analyze the photon migration in a mult-layered tissue and to optimize the design of the transducer.