Fukutomi D, Ishii K, Awazu K
Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
Lasers Med Sci. 2015 May;30(4):1335-40. doi: 10.1007/s10103-015-1734-5. Epub 2015 Mar 15.
An integrating sphere system has been used to investigate the estimation error in the scattering coefficient for biological tissues. Since the angular distribution of diffusely reflected light from a sample may depend on the sample absorbance, leakage at the entrance port may affect estimates of the scattering coefficient based on measurement of diffuse reflectance. In the present study, the dependence of the angular distribution of the diffusely reflected light on the hemoglobin (Hb) concentration in a sample was investigated. Subsequently, the effect of the entrance port diameter on the error in the scattering coefficient estimated based on diffuse reflectance measurements was evaluated. For a biological tissue phantom, the angular reflectance distribution at a wavelength of 405 nm, at which strong absorption occurred, showed an increasing bias toward specular reflection as the Hb concentration was increased. No such concentration dependence was found at a wavelength of 664 nm, where the absorbance was low. In addition, it was found that the estimation error in the scattering coefficient was reduced for smaller entrance port diameters. Therefore, when attempting to determine the scattering coefficient for strongly absorbing samples, it is necessary to consider both the angular distribution of the diffusely reflected light and the optimal entrance port diameter.
已使用积分球系统来研究生物组织散射系数的估计误差。由于来自样品的漫反射光的角分布可能取决于样品吸光度，入口处的泄漏可能会影响基于漫反射测量的散射系数估计。在本研究中，研究了漫反射光的角分布对样品中血红蛋白（Hb）浓度的依赖性。随后，评估了入口直径对基于漫反射测量估计的散射系数误差的影响。对于生物组织模型，在发生强吸收的405nm波长处的角反射率分布显示，随着Hb浓度的增加，向镜面反射的偏差增大。在吸光度较低的664nm波长处未发现这种浓度依赖性。此外，还发现较小的入口直径可降低散射系数的估计误差。因此，在尝试确定强吸收样品的散射系数时，有必要同时考虑漫反射光的角分布和最佳入口直径。
