Evaluation of image reconstruction algorithm for near infrared topography by virtual head phantom

The poor spatial resolution and reproducibility of the images are disadvantages of near infrared topography. The authors proposed the combination of the double-density probe arrangement and the image reconstruction algorithm using a spatial sensitivity profile to improve the spatial resolution and the reproducibility. However, the proposed method was evaluated only by the simplified adult head model. It is uncertain whether the proposed method is effective to the actual head that has complicated structure. In this study, the proposed method is evaluated by the virtual head phantom the 3D-structure of which is based upon an MRI scan of an adult head. The absorption change the size of which is almost equivalent to the width of the brain gyri was measured by the conventional method and the proposed method to evaluate the spatial resolution of the topographic images obtained by each method. The positions of the probe arrangements are slightly changed and the topographic images of the same brain activation measured by two probe positions are compared to evaluate the reproducibility of the NIR topography. The results indicate that the combination of the double-density probe arrangement and the image reconstruction algorithm using the spatial sensitivity profile can improve both the spatial resolution and the reproducibility of the topographic image of brain activation in the virtual head phantom. However, the uneven thickness of the superficial tissues affects the accuracy of the position of activation in the images.