Theoretical evaluation of accuracy in position and size of brain activity obtained by near-infrared topography
Theoretical evaluation of accuracy in position and size of brain activity obtained by near-infrared topography
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DOI：
10.1088/0031-9155/49/12/019
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发表时间：
2004-06-21
影响因子：
3.5
通讯作者：
Okada, E
中科院分区：
文献类型：
--
作者：
Kawaguchi, H;Hayashi, T;Okada, E
近红外（NIR）地形图可以获得大脑皮层激活区域的地形分布。近红外光在头部中强烈散射，并且由头部表面上的源-检测器对采样的组织的体积广泛分布在大脑中。这种散射效应导致大脑活动的地形图图像的分辨率和对比度差。本研究通过映射和重建方法计算了头部模型中吸收变化的一维分布，以评估图像重建算法和测量点的间隔对地形成像的精度的影响。通过蒙特卡罗模拟，预测了头部模型中的光传播，以获得源-探测器对的空间灵敏度分布。测量点是一维排列在模型的表面上，相邻测量点之间的距离从4 mm到28 mm不等。测量点的小间隔改善了通过映射和重建方法计算的地形图像。在传统的映射方法中，空间分辨率的极限取决于测量点的间隔和源-探测器对的空间灵敏度分布。当测量点间距小于12 mm时，重建方法优于映射方法，改善了一维分析的结果。空间灵敏度剖面的重叠效应表明，重建方法可以有效地改善测量点间距较大时获得的二维重建图像的空间分辨率。利用该重建方法的近红外地形图潜在地获得脑中吸收变化的准确分布，即使吸收变化的尺寸小于10 mm。
Near-infrared (NIR) topography can obtain a topographical distribution of the activated region in the brain cortex. Near-infrared light is strongly scattered in the head, and the volume of tissue sampled by a source-detector pair on the head surface is broadly distributed in the brain. This scattering effect results in poor resolution and contrast in the topographic image of the brain activity. In this study, a one-dimensional distribution of absorption change in a head model is calculated by mapping and reconstruction methods to evaluate the effect of the image reconstruction algorithm and the interval of measurement points for topographic imaging on the accuracy of the topographic image. The light propagation in the head model is predicted by Monte Carlo simulation to obtain the spatial sensitivity profile for a source-detector pair. The measurement points are one-dimensionally arranged on the surface of the model, and the distance between adjacent measurement points is varied from 4 mm to 28 mm. Small intervals of the measurement points improve the topographic image calculated by both the mapping and reconstruction methods. In the conventional mapping method, the limit of the spatial resolution depends upon the interval of the measurement points and spatial sensitivity profile for source-detector pairs. The reconstruction method has advantages over the mapping method which improve the results of one-dimensional analysis when the interval of measurement points is less than 12 mm. The effect of overlapping of spatial sensitivity profiles indicates that the reconstruction method may be effective to improve the spatial resolution of a two-dimensional reconstruction of topographic image obtained with larger interval of measurement points. Near-infrared topography with the reconstruction method potentially obtains an accurate distribution of absorption change in the brain even if the size of absorption change is less than 10 mm.