Effective scattering coefficient of the cerebral spinal fluid in adult head models for diffuse optical imaging
Effective scattering coefficient of the cerebral spinal fluid in adult head models for diffuse optical imaging
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DOI：
10.1364/ao.45.004747
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发表时间：
2006-07-01
期刊：
影响因子：
1.9
通讯作者：
Boas, David A.
中科院分区：
文献类型：
--
作者：
Custo, Anna;Wells, William M., III;Boas, David A.
有效计算头部模型中光子传输的时间相关正向解是对大脑功能性漫射光学成像进行精确反演的关键能力。光子输运的扩散近似比物理上正确的辐射输运方程（RTE）更快;然而，通常假设散射长度必须远小于所有系统尺寸和所有吸收长度，近似才准确。这些条件在脑脊液（CSF）中均不满足。由于CSF中的视线距离很小，大约为几毫米，我们探索了这样的想法，即CSF散射系数可以由从零到典型的反向视线距离的数量级或大约0.3 mm（-1）的任何值来建模，而不会显著改变计算的检测器信号或与功能测量相关的部分路径长度。我们证明了这一点，通过使用Monte Carlo模拟的RTE在一个三维头部模型的基础上，临床磁共振成像数据，与现实的光极几何形状。我们的研究结果使我们预期，扩散近似将是有效的，即使在CSF的存在下，与更快的逆问题的解决方案的后果。(c)2006年美国光学学会。
An efficient computation of the time-dependent forward solution for photon transport in a head model is a key capability for performing accurate inversion for functional diffuse optical imaging of the brain. The diffusion approximation to photon transport is much faster to simulate than the physically correct radiative transpart equation (RTE); however, it is commonly assumed that scattering lengths must be much smaller than all system dimensions and all absorption lengths for the approximation to be accurate. Neither of these conditions is satisfied in the cerebrospinal fluid (CSF). Since line-of-sight distances in the CSF are small, of the order of a few millimeters, we explore the idea that the CSF scattering coefficient may be modeled by any value from zero up to the order of the typical inverse line-of-sight distance, or approximately 0.3 mm(-1), without significantly altering the calculated detector signals or the partial path lengths relevant for functional measurements. We demonstrate this in detail by using a Monte Carlo simulation of the RTE in a three-dimensional head model based on clinical magnetic resonance imaging data, with realistic optode geometries. Our findings lead us to expect that the diffusion approximation will be valid even in the presence of the CSF, with consequences for faster solution of the inverse problem. (c) 2006 Optical Society of America.