漫反射光谱测量压力作用下皮肤组织中水含量变化

Measurement of Water Variation Within Skin under Probe Pressure by Diffuse Reflectance Spectroscopy

在体漫反射光谱测量中常采用接触式测量方式,光纤测头压力对测量精度有很大影响.本文基于生物组织固液两相模型,研究了光纤测头压力作用下组织形变和成分变化机理.分别测量生物组织随压力大小和作用时间变化的漫反射光谱,并进行二阶导数处理,根据1 160 nm和1 220 nm两个波长吸收峰变化,得到生物组织中自由水和结合水含量改变,从而得到组织形变过程.实验结果表明,生物组织中的自由水和结合水体积变化与压力大小以及作用时间呈非线性关系,并与生物组织生理状态密切相关.在体光谱测量中应控制光纤测头压力小于200 kPa,以避免组织中结合水转化成自由水.本文的研究结果为漫反射光谱测量部位和测量策略选择提供了参考.

In the measurement of in vivo diffuse reflectance spectrum, the contact method is widely adopted. The external pressure caused by fiber optic probe may influence the accuracy of measurement. According to the solid-liquid biphasic mixture model, the mechanism of tissue deformation and composition change under certain compression is researched. The diffuse reflectance spectra of tissue with the increase of pressure and duration are measured and transformed into second-derivation spectra. The amplitudes of 1 160 nm and 1 220 nm in the second-derivative spectra are related to the contents of bulk and bound water in the tissue which reflects the process of tissue deformation. Experimental results indicate that the variations of bulk and bound water in tissue have a non-linear relationship with the pressure and duration. It is also affected by the differences of tissue structure and physiological status. When the in vivo skin is measured, the pressure of probe should be limited to less than 200 kPa to prevent the bound water in skin from changing into bulk water. Future research on the selections of measurement site and strategy of diffuse reflectance spectra might benefit from the results of this paper.