Kienle A, Lilge L, Patterson M S, Hibst R, Steiner R, Wilson B C
Appl Opt. 1996 May 1;35(13):2304-14. doi: 10.1364/AO.35.002304.
The absorption and transport scattering coefficients of biological tissues determine the radial dependence of the diffuse reflectance that is due to a point source. A system is described for making remote measurements of spatially resolved absolute diffuse reflectance and hence noninvasive, noncontact estimates of the tissue optical properties. The system incorporated a laser source and a CCD camera. Deflection of the incident beam into the camera allowed characterization of the source for absolute reflectance measurements. It is shown that an often used solution of the diffusion equation cannot be applied for these measurements. Instead, a neural network, trained on the results of Monte Carlo simulations, was used to estimate the absorption and scattering coefficients from the reflectance data. Tests on tissue-simulating phantoms with transport scattering coefficients between 0.5 and 2.0 mm(-1) and absorption coefficients between 0.002 and 0.1 mm(-1) showed the rms errors of this technique to be 2.6% for the transport scattering coefficient and 14% for the absorption coefficients. The optical properties of bovine muscle, adipose, and liver tissue, as well as chicken muscle (breast), were also measured ex vivo at 633 and 751 nm. For muscle tissue it was found that the Monte Carlo simulation did not agree with experimental measurements of reflectance at distances less than 2 mm from the incident beam.
生物组织的吸收系数和输运散射系数决定了由点光源引起的漫反射率的径向依赖性。本文描述了一种用于对空间分辨的绝对漫反射率进行远程测量的系统，从而对组织光学特性进行无创、非接触式估计。该系统包括一个激光源和一个电荷耦合器件（CCD）相机。将入射光束偏转到相机中，可对光源进行表征，以进行绝对反射率测量。结果表明，扩散方程的一种常用解不适用于这些测量。取而代之的是，使用一个基于蒙特卡罗模拟结果训练的神经网络，从反射率数据中估计吸收系数和散射系数。对输运散射系数在0.5至2.0 mm⁻¹之间且吸收系数在0.002至0.1 mm⁻¹之间的组织模拟体模进行测试，结果表明该技术对输运散射系数的均方根误差为2.6%，对吸收系数的均方根误差为14%。还在离体状态下于633和751 nm波长处测量了牛肌肉、脂肪和肝脏组织以及鸡肌肉（胸肌）的光学特性。对于肌肉组织，发现蒙特卡罗模拟在距入射光束小于2 mm的距离处与反射率的实验测量结果不一致。
