Sato Chie, Shimada Miho, Yamada Yukio, Hoshi Yoko
Tokyo Institute of Psychiatry, Department of Integrated Neuroscience, 2-1-8 Kamikitazawa, Setagaya-ku, Tokyo 156-8585, Japan.
J Biomed Opt. 2005 Nov-Dec;10(6):064008. doi: 10.1117/1.2136312.
We try a new approach with near-IR time-resolved spectroscopy, to separate optical signals originated in the upper layer from those in the lower layer and to selectively determine the absorption coefficient (mu(a)) of each layer in a two-layered turbid medium. The difference curve in the temporal profiles of light attenuation between a target and a reference medium is divided into segments along the time axis, and a slope of each segment is calculated to determine the depth-dependent mu(a). The depth-dependent mu(a) values are estimated under various conditions in which mu(a) and the reduced scattering coefficient (mu(s)') of each layer are changed with a Monte Carlo simulation and in phantom experiments. Temporal variation of them represents the difference in mu(a) between two layers when mu(s)' of a reference is the same as that of the upper layer of the target. The discrepancies between calculated mu(a) and the real mu(a) depend on the ratio of the real mu(a) of the upper layer to that of the lower layer, and our approach enables us to estimate the ratio of mu(a) between the two layers. These results suggest the potential that mu(a) of the lower layer can be determined by our procedure.
我们尝试采用近红外时间分辨光谱的新方法，以分离上层产生的光信号与下层产生的光信号，并选择性地确定双层混浊介质中各层的吸收系数（μ(a)）。将目标介质与参考介质之间光衰减时间轮廓的差异曲线沿时间轴划分为若干段，并计算每段的斜率以确定深度依赖的μ(a)。在各种条件下估计深度依赖的μ(a)值，其中通过蒙特卡罗模拟和体模实验改变各层的μ(a)和约化散射系数（μ(s)'）。当参考介质的μ(s)'与目标上层的μ(s)'相同时，它们的时间变化表示两层之间μ(a)的差异。计算得到的μ(a)与实际μ(a)之间的差异取决于上层实际μ(a)与下层实际μ(a)的比值，我们的方法使我们能够估计两层之间μ(a)的比值。这些结果表明，我们的方法有潜力确定下层的μ(a)。
