基于混合漫射近似的空间分辨漫反射光学参量灵敏度的研究

根据空间分辨漫反射的双点源混合漫射近似模型, 推导了空间分辨漫反射率对生物组织吸收系数μ_a和有效散射系数μ'_s灵敏度的解析表示, 系统研究了在强吸收条件近光源区域吸收系数μ_a和有效散射系数μ'_s对漫反射光子分布的影响. 研究表明: 吸收系数的灵敏度随光源与探测器间距ρ的增加呈线性增长, 其斜率正比于(μ'_s/μ_a)^1/4, 比例系数约为1.4, 同时获得一个优化的探测距离ρ_opt, 距离光源约3.4个输运平均自由程, 在这个距离处有效散射系数的变化对测量吸收的影响最小. 这项研究对于生物组织的光学性质测量以及漫反射光谱技术的应用具有重要意义.

Sensitivity of spatially-resolved diffuse reflectance to optical parameters in the hybrid diffusion approximation

Based on a theoretical model for spatial diffusion reflection with two-point-source hybrid diffusion approximate to a semi-infinite homogeneous turbid medium,expressions of the sensitivities for the absorption coefficientμ_a and the reduced scattering coefficientμ’s are derived,and the effect of the sensitivities of the two optical parametersμ_a andμ’_s on diffuse reflectance is studied systematically in small volumes of highly absorbing medium.The results show that the sensitivity of the absorption coefficient increases approximately linearly with the increase of source-detector separation p,with a slope proportional to 1.4（μ’s/μ_a）^1/4,and also indicate an optimal probe spacingρ_opt at which a variable reduced scattering coefficient has a smallest effect on the measurment of optical absorption in the turbid medium.The value ofρ_opt is approximately equal to 3.4 times transport mean free path.The study is of great significance for the measurment of the optical properties of biological tissues and the application of diffuse reflecance spectroscopy technology.