Development of a tissue oxygen monitor using near-infrared light with correction for influence of tissue inhomogeneity and quantitaive evaluation of muscle metabolism

本研究的目的是开发一种组织氧监测仪，可以消除脂肪层对近红外光谱（NIRS）测量肌肉氧合的影响，并通过验证该技术在运动医学领域的有效性，建立定量NIRS.肌肉和脂肪组织的平均光学特性（吸收和散射系数）通过比较使用时间分辨近红外光谱的体内测量结果与使用多层模型的蒙特卡罗模拟的结果来确定.基于扩散理论，从理论上推导了一种用于组织氧含量测量的非线性算法，并根据肌肉的平均光学特性确定了算法系数.提出了一种消除脂肪层对测量灵敏度影响的修正方法，使均匀介质假设下的理论算法得以应用。磁共振波谱也证实了该校正方法的有效性.作为近红外光谱技术在运动生理学中的应用，对13名北欧滑雪国家队优秀运动员高原训练后肌肉氧合恢复率进行了测定。结果发现，在训练开始后的第6天和第11天，恢复率分别提高了11%和20%.开发了用于估计肌肉代谢的新的测量技术：肌肉中的血氧饱和度和肌肉的耗氧量分别从收缩期间血容量的变化和肌肉氧合的降低速率来估计。开发了一种200通道肌肉氧合成像系统：在大腿上成功地成像了膝关节伸展和屈曲过程中氧合血红蛋白和脱氧血红蛋白的时空变化。

The objectives of this study were to develop a tissue oxygen monitor that can eliminate the influence of a fat layer on muscle oxygenation measurement using near-infrared spectroscopy (NIRS) and to establish quantitative NIRS by verifying the validity of this technique in the field of sports medicine.1. Mean optical properties (absorption and scattering coefficients) of muscle and adipose tissues were determined by comparing results of in vivo measurements using time-resolved NIRS with those of Monte Carlo simulation using a multi-layered model.2. A nonlinear algorithm for tissue oxygenation measurement was theoretically derived, based on diffusion theory, and the coefficients of the algorithm were determined from the mean optical properties of muscles.3. A correction method for eliminating the great influence of a fat layer on measurement sensitivity was developed so that the theoretical algorithm assuming a homogeneous medium could be applied. Validity of this correction method was also confirmed by magnetic resonance spectroscopy.4. As an application of NIRS to exercise physiology, restoration rates of muscle oxygenation after exercise n were measured in 13 top athletes of National Team for Nordic skiing during high-altitude training. It was found that the restoration rates increased by 11 % and 20 % at 6 and 11 days after the beginning of the training, respectively.5. New measurement techniques for estimating muscle metabolism were developed: oxygen saturation of blood in muscles and oxygen consumption of muscles were estimated from change in blood volume and from a decreasing rate of muscle oxygenation, respectively, during contraction.6. A 200-channel imaging system of muscle oxygenation was developed: and spatio-temporal changes in oxy- and deoxy-hemoglobin during knee extension and flexion were successfully imaged on the thigh.