基于漫反射光谱的组织光学参数测量系统与方法研究

在体组织光学参数测量是生物医学光子学研究重点，不仅为人体成分无创检测、光学成像、光动力疗法等研究提供基础，并且可以快速获取人体光学参数变化，为临床诊断提供依据。研究了利用单一源探距离漫反射光谱在体测量光学参数的测量系统与反构方法。漫反射光谱测量系统由宽谱光源、高分辨光纤光谱仪及光纤探头组成，结构简单，测量方便，可准确快速测量样品漫反射光谱。在光纤探头几何形状基础上，研究了光纤收集及系统传递函数，在此基础上对反构算法进行了校正。光学参数反构算法中正向模型基于Monte Carlo以及神经网络方法，适用光学参数范围大，计算速度快;逆向算法采用主成分分析与非线性建模拟合相结合的方法，可抑制测量噪声影响。在测量系统及反构算法基础上，进行了组织仿体光学参数测量实验，结果表明，利用单一源探距离下漫反射谱，可以较为准确获取吸收系数以及约化散射系数，均方根误差分别达到4.58%以及7.92%。为保证系统测量准确性，测量波长范围应覆盖样品中所含吸收物质吸收峰范围。所研究的在体组织光学参数测量方法为人体成分无创检测及测量条件变化获取提供了基础。

Study on the Determination System of Tissue Optical Properties Based on Diffuse Reflectance Spectrum

The determination of tissue optical properties is the fundamental research field in biomedical optics.The ability to separately quantify absorption and scattering coefficients of tissue based on diffuse reflectance spectrum not only helps to gain physiological and structural properties of tissue but also provide insight into the mechanisms of tissue,which leads to the im-provement in non-invasive detecting,image diagnosis and photodynamic therapy.In the paper,a flexible and rapid method is de-veloped to extract the absorption and reduced scattering coefficients of turbid medium such as human tissue with diffuse reflec-tance spectrum.The diffuse reflectance spectrum is measured by the system which includes a white light source,a spectrometer, and a fiber optic probe for delivery and collection of light.The collection efficiency and system transfer function are researched based on the fiber probe geometry.This paper outlines a method based on empirical forward model and non-linear modeling in-verse model to extract the optical properties from diffuse reflectance spectrum.The approach includes four steps:(1)generating diffuse reflectance spectra for training inverse model;(2)training the inverse model;(3)measuring and processing the diffuse reflectance spectra of samples;(4)predicting the optical properties of samples.Since the forward and inverse models could be regarded as non-linearity,the Artificial Neural Networks (ANN)is employed to develop the forward and inverse models.The principal component analysis (PCA)is also employed in the inverse model to decompress the data dimension and suppress the spectral noise.With a single fiber optic probe and spectroscopy system,the diffuse reflectance spectrum is measured and prepro-cessed.The accuracy and robustness of this method are evaluated by measuring the phantoms with a wide range of optical prop-erties.The results indicate that the absorption and scattering coefficients could be extracted accurately by measuring the diffuse reflectance spectrum of single source-detector distance.The mean RMS percentage error is 4.58% and 7.92%,respectively.As to the application of extracting concentration of different chromosphere,it is better to include the absorption peak of every chro-mosphere within the measuring wavelength range.This method is valid for a wide range of optical properties with the advantage of rapid measurement and simple system setup,which is important for the clinical application.