A wearable optical topography system was developed that is based on near-infrared spectroscopy (NIRS) for observing brain activity noninvasively including in regions covered by hair. An avalanche photo diode, high voltage dc-dc converter, and preamplifier were placed in an electrically shielded case to be safely mounted on the head. Rubber teeth and a glass rod were prepared to clear away hair and reach the scalp. These devices realized for the first time a wearable NIRS imager for any region of the cortex. The activity in the motor cortex during finger tapping was successfully observed.

The detector module using CdTe with edge-on configuration was developed. The pixel pitch is 1.4 mm, and 1024 pixels constitute the field of view of 45 mm square. The CdTe crystals sandwich thin circuit boards to form CdTe cards, and 16 CdTe cards are mounted on the module. The intrinsic energy resolution of 4.4% (FWHM) was achieved with Tc-99m at CdTe temperature of 25 o C. It remains 5.1% at 40 o C, which implies the possibility of air-cooling system. Uniformity and count-rate performance were also evaluated.

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