Takatsuki Akira, Eda Hideo, Yanagida Toshio, Seiyama Akitoshi
Department of Biophysical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka, 560-8531 Japan.
Jpn J Physiol. 2004 Feb;54(1):79-86. doi: 10.2170/jjphysiol.54.79.
The spatial resolution of near infrared spectroscopic imaging in brain function mapping studies needs to be improved. Most near infrared spectroscopic imaging systems use optical fibers that are arranged like a lattice. The light source and the detector have one-on-one correspondence at intervals of about 3 cm. In this study, we apply several detectors against one source to improve spatial resolution. We assume that a local absorber within a strong scattering medium is a model for local cerebral activation. When we calculate absorbance, which is used to spectroscopically calculate hemoglobin concentration, the peak position shifts away from above the position where an absorber is located. As far as absorbance is calculated, we cannot obtain spatial information about the absorber even if many detectors are used against one source. When we calculate the difference between detected light intensities, however, we demonstrate that an absorber projected onto the measuring surface has an influence directly above it. We predict this property from a light diffusion equation and also prove it experimentally through measurements of a uniform resinous phantom with an absorber. This is one of the basic principles supporting the achievement of higher spatial resolutions with near infrared spectroscopic imaging.
在脑功能映射研究中，近红外光谱成像的空间分辨率有待提高。大多数近红外光谱成像系统使用呈晶格状排列的光纤。光源和探测器以约3厘米的间隔一一对应。在本研究中，我们针对一个光源应用多个探测器以提高空间分辨率。我们假定强散射介质中的局部吸收体是局部脑激活的模型。当我们计算用于光谱计算血红蛋白浓度的吸光度时，峰值位置会从吸收体所在位置上方偏移。就吸光度的计算而言，即使针对一个光源使用多个探测器，我们也无法获得吸收体的空间信息。然而，当我们计算检测到的光强度之间的差异时，我们证明投射到测量表面上的吸收体在其正上方有直接影响。我们从光扩散方程预测了这一特性，并通过对带有吸收体的均匀树脂模型进行测量，实验证明了这一点。这是支持通过近红外光谱成像实现更高空间分辨率的基本原理之一。
