Its very important to improve the sensitivity of the near- infrared tissue oximeter during practical non-invasive measurement on human muscle. It has been thought that this sensitivity is influenced by the existence of overlying tissues such as skin and fat because only those photons which have passed through the muscle bring back useful information. In this paper, the influences of fat layer, detecting distance, wavelength, and the oxygenation in muscle on photon partial path length in muscle layer are discussed based on Monte-Carlo simulation results. Also examined are the statistical error in simulation and the noise in detector. Finally, the experimental results of the cuff occlusion on forearm are given. The results show the relationship between the sensitivity of the tissue oximeter and the detecting distance, which has the same tendency as the simulation predicted.
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