漫反射接触测量中压力不敏感径向检测位置存在性研究

近红外无创漫反射检测中光纤探头与被测组织之间接触压力变化会导致测量准确性和稳定性较差。以压力不敏感径向检测位置采集漫反射光信号，以此削弱接触压力带来的测量误差，并在Monte Carlo模拟与在体实验中验证了压力不敏感位置的存在性。首先，结合人体皮肤结构模型和力学特性，建立了接触压力与皮肤组织参数之间的定量关系，并利用Monte Carlo模拟仿真分析了不同接触压力下1 000～1 320 nm波段内，不同径向检测距离处漫反射光强的变化；其次，搭建了基于超辐射发光二极管光源的多环光纤束检测系统，在体测量了三位志愿者在不同压力下的漫反射光信号。最后，评价了人体压力不敏感径向检测位置与其他位置处接收的光信号稳定性。模拟结果表明，在距入射径向距离1.3～1.5 mm范围内，接收到的漫反射光强近似不受压力变化影响，即存在压力不敏感径向检测位置。在体实验表明，在1 050，1 219和1 314 nm波长下均存在压力不敏感径向检测位置，位于距入射点0.78～1.0 mm范围内，初步验证了压力不敏感径向检测位置在人体的存在性，与其他径向位置相比，在压力不敏感径向检测位置处测得光强信号信噪比更高。因此，基于压力不敏感径向检测位置的测量方法可以有效降低接触压力变化对接收光谱的影响，有望提高近红外无创漫反射检测的精度。

Existence of Pressure-Insensitive Radial Position in Diffuse Reflection Contact Measurement

The variation of probe-tissue contact pressure will lead to poor measurement accuracy and stability in the near-infrared noninvasive diffuse reflection measurement. In this paper, the pressure-insensitive radial position was proposed to collect the diffuse reflection signal to minimize the measurement error caused by contact pressure, and the existence of pressure-insensitive radial position was verified by Monte Carlo simulation and in vivo experiment. First, Combined with human skin structure model and mechanical properties, the quantitative relationship between contact pressure and skin tissue parameters were established, and the distribution change of diffuse light intensity along radial distance within the wavelength of 1 000～1 320 nm under different contact pressure was simulated by the Monte Carlo program. Then the diffuse reflection detection system configured with the super-luminescence diodes and customized optical fibers were built, where multiple detector fibers surrounded the source fiber. And in vivo experiments were performed where the diffuse reflection signals in the wavelength of 1 050, 1 219 and 1 314 nm of three volunteers were collected under different pressure. Last, the stability of signal received from pressure-insensitive radial position and other radial position was evaluated. Simulation results showed that, the diffuse reflection signals received within the radial distance from 1.3 to 1.5 mm were not changed with the contact pressure, which means there were the pressure-insensitive radial positions. The experiment results of in vivo showed that, the pressure-insensitive radial positions could be found in all the volunteers, and they were located within the radial distance of 0.78～1.0 mm for the all wavelengths investigated. Compared with other radial positions, the signal-to-noise ratio of the signal collected under the pressure-insensitive radial position was higher. Therefore, the measurement method based on the pressure-insensitive radial position can effectively reduce the influence of the contact-pressure variation on the spectral information, and it is expected to improve the accuracy of the near-infrared noninvasive diffuse reflection measurement.