<title>Accurate NIRS measurement of muscle oxygenation by correcting the influence of a subcutaneous fat layer</title>

Abstract

Although the inhomogeneity of tissue structure affects the sensitivity of tissue oxygenation measurement by reflectance near-infrared spectroscopy, few analyses of this effect have been reported. In this study, the influence of a subcutaneous fat layer on muscle oxygenation measurement was investigated by Monte Carlo simulation and experimental studies. In the experiments, measurement sensitivity was examined by measuring the falling rate of oxygenation in occlusion tests on the forearm using a tissue oxygen monitor. The fat layer thickness was measured by ultrasonography. Results of the simulation and occlusion tests clearly showed that the presence of a fat layer greatly decreases the measurement sensitivity and increases the light intensity at the detector. The correction factors of sensitivity were obtained from this relationship and were successfully validated by experiments on 12 subjects whose fat layer thickness ranged from 3.5 to 8 mm.