Ripoll Jorge, Yessayan Doreen, Zacharakis Giannis, Ntziachristos Vasilis
Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, Heraklion, Crete, Greece.
J Opt Soc Am A Opt Image Sci Vis. 2005 Mar;22(3):546-51. doi: 10.1364/josaa.22.000546.
Optical imaging and tomography in tissues can facilitate the quantitative study of several important chromophores and fluorophores. Several theoretical models have been validated for diffuse photon propagation in highly scattering and low-absorbing media that describe the optical appearance of tissues in the near-infrared (NIR) region. However, these models are not generally applicable to quantitative optical investigations in the visible because of the significantly higher tissue absorption in this spectral region compared with that in the NIR. We performed photon measurements through highly scattering and absorbing media for ratios of the absorption coefficient to the reduced scattering coefficient ranging approximately from zero to one. We examined experimentally the performance of the absorption-dependent diffusion coefficient defined by Aronson and Corngold [J. Opt. Soc. Am. A 16, 1066 (1999)] for quantitative estimations of photon propagation in the low- and high-absorption regimes. Through steady-state measurements we verified that the transmitted intensity is well described by the diffusion equation by considering a modified diffusion coefficient with a nonlinear dependence on the absorption. This study confirms that simple analytical solutions based on the diffusion approximation are suitable even for high-absorption regimes and shows that diffusion-approximation-based models are valid for quantitative measurements and tomographic imaging of tissues in the visible.
组织中的光学成像和层析成像有助于对几种重要的发色团和荧光团进行定量研究。已经验证了几种理论模型用于描述近红外（NIR）区域中组织光学外观的高散射和低吸收介质中的漫射光子传播。然而，由于与近红外区域相比，该光谱区域中的组织吸收明显更高，这些模型通常不适用于可见光中的定量光学研究。我们对吸收系数与约化散射系数之比大致从零到一的高散射和吸收介质进行了光子测量。我们通过实验研究了由阿隆森和康戈尔德定义的吸收相关扩散系数[《美国光学学会志A》16, 1066 (1999)]在低吸收和高吸收状态下对光子传播进行定量估计的性能。通过稳态测量，我们验证了通过考虑对吸收具有非线性依赖性的修正扩散系数，扩散方程能很好地描述透射强度。这项研究证实，基于扩散近似的简单解析解即使对于高吸收状态也适用，并表明基于扩散近似的模型对于可见光中组织的定量测量和层析成像有效。
