Hybrid Monte Carlo-diffusion method for light propagation in tissue with a low-scattering region
Hybrid Monte Carlo-diffusion method for light propagation in tissue with a low-scattering region
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DOI：
10.1364/ao.42.002888
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发表时间：
2003-06-01
期刊：
影响因子：
1.9
通讯作者：
Okada, E
中科院分区：
文献类型：
--
作者：
Hayashi, T;Kashio, Y;Okada, E
头部组织的异质性，特别是围绕大脑的低散射脑脊液（CSF）层，先前已被证明会强烈影响大脑中的光传播。采用辐射度-扩散方法，假设光在CSF层中的传播服从辐射度理论，预测了光在头部模型中的传播。尽管在放射性扩散方法中CSF层被假定为非散射区域，但在真实的头部中，精细的蛛网膜小梁在CSF层中引起微弱的散射。提出了一种新的方法，混合蒙特卡罗扩散方法，计算头部模型，包括低散射区，其中光传播不服从扩散近似和辐射度理论。高散射区的光传输采用扩散近似的有限元方法计算，低散射区的光传输采用蒙特卡罗方法计算。混合方法计算的具有低散射CSF层的头部模型的检测光的强度和平均飞行时间与Monte Carlo方法的结果一致，而通过扩散近似计算的结果包括CSF层的影响所引起的相当大的误差。在混合方法中，耗时的Monte Carlo计算仅用于薄CSF层，因此，混合方法的计算时间显著短于Monte Carlo方法。(C)2003年美国光学学会。
The heterogeneity of the tissues in a head, especially the low-scattering cerebrospinal fluid (CSF) layer surrounding the brain has previously been shown to strongly affect light propagation in the brain. The radiosity-diffusion method, in which the light propagation in the CSF layer is assumed to obey the radiosity theory, has been employed to predict the light propagation in head models. Although the CSF layer is assumed to be a nonscattering region in the radiosity-diffusion method, fine arachnoid trabeculae cause faint scattering in the CSF layer in real heads. A novel approach, the hybrid Monte Carlo-diffusion method, is proposed to calculate the head models, including the low-scattering region in which the light propagation does not obey neither the diffusion approximation nor the radiosity theory. The light propagation in the high-scattering region is calculated by means of the diffusion approximation solved by the finite-element method and that in the low-scattering region is predicted by the Monte Carlo method. The intensity and mean time of flight of the detected light for the head model with a low-scattering CSF layer calculated by the hybrid method agreed well with those by the Monte Carlo method, whereas the results calculated by means of the diffusion approximation included considerable error caused by the effect of the CSF layer. In the hybrid method, the time-consuming Monte Carlo calculation is employed only for the thin CSF layer, and hence, the computation time of the hybrid method is dramatically shorter than that of the Monte Carlo method. (C) 2003 Optical Society of America.