Investigation of the appropriate source-detector distance in functional near-infrared spectroscopy of macaque monkey brain

Abstract

The optimal SD distance for functional near infrared spectroscopy of macaque monkey has investigated with the simulation calculations of light propagation in the sophisticated head model. T1- and T2-weighted images of monkeys (N=2) were segmented into 6 regions. Optical properties assigned to each region were referred from literatures. A pair of probes was located on the scalp surface above the motor cortex with changing the SD distance (10, 15, 20 and 25 mm) and the direction (perpendicular or parallel to central sulcus). The analytical solution of the diffusion equation was calculated by the finite element method. The detected intensity and partial optical path length in the gray matter was decreased and increased by the increase of the SD distance, respectively. The product of the intensity and the path length showed high value for the SD distance was 15 mm regardless of subjects and directions.