Koyama Tatsuya, Iwasaki Atsushi, Ogoshi Yosuke, Okada Eiji
Department of Electronics and Electrical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
Appl Opt. 2005 Apr 10;44(11):2094-103. doi: 10.1364/ao.44.002094.
A practical and adequate approach to modeling light propagation in an adult head with a low-scattering cerebrospinal fluid (CSF) region by use of diffusion theory was investigated. The diffusion approximation does not hold in a nonscattering or low-scattering regions. The hybrid radiosity-diffusion method was adopted to model the light propagation in the head with a nonscattering region. In the hybrid method the geometry of the nonscattering region is acquired as a priori information. In reality, low-level scattering occurs in the CSF region and may reduce the error caused by the diffusion approximation. The partial optical path length and the spatial sensitivity profile calculated by the finite-element method agree well with those calculated by the Monte Carlo method in the case in which the transport scattering coefficient of the CSF layer is greater than 0.3 mm(-1). Because it is feasible to assume that the transport scattering coefficient of a CSF layer is 0.3 mm(-1), it is practical to adopt diffusion theory to the modeling of light propagation in an adult head as an alternative to the hybrid method.
研究了一种实用且充分的方法，即利用扩散理论对成人头部中具有低散射脑脊液（CSF）区域的光传播进行建模。扩散近似在非散射或低散射区域不成立。采用混合辐射度 - 扩散方法对具有非散射区域的头部光传播进行建模。在混合方法中，非散射区域的几何形状作为先验信息获取。实际上，脑脊液区域会发生低水平散射，这可能会减少由扩散近似引起的误差。在脑脊液层的输运散射系数大于0.3 mm⁻¹ 的情况下，通过有限元方法计算的部分光程长度和空间灵敏度分布与通过蒙特卡罗方法计算的结果吻合良好。由于假设脑脊液层的输运散射系数为0.3 mm⁻¹ 是可行的，因此采用扩散理论对成人头部光传播进行建模作为混合方法的替代方案是切实可行的。
