Near infrared topographic imaging is effective to obtain the functional image of brain-cortex. The image is reconstructed from the change in light intensity detected with multi- channel source-detector pairs. Since the volume of brain tissue sampled by each source-detector pair is affected the scattering of tissue, it is important to evaluate the effect of scattering on the spatial resolution of the reconstructed image. In this study, the absorption change of various sizes at various positions in the adult head phantom is reconstructed by multi-channel measurements to evaluate the spatial resolution of topographic imaging. Since the heterogeneity of tissue, especially presence of low scattering CSF layer, affects the light propagation in the adult brain, the phantom consists of three layers. The diameter of the absorber is varied from 10 to 20 mm. The position of reconstructed absorber in the topographic image agrees well with that of the absorber in the brain layer of the phantom. The size of reconstructed absorber in the images is considerably broader than that of the absorber.
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