Development of a Brain PET System, PET-Hat: A Wearable PET System for Brain Research

Brain functional studies using PET have advantages over fMRI in some areas such as auditory research in part because PET systems produce no acoustic noise during acquisition. However commercially available PET systems are designed for whole body studies and are not optimized for brain functional studies. We developed a low cost, small, wearable brain PET system named PET-Hat dedicated for brain imaging. It employs double counter-balanced systems for mechanical supports of the detector ring while allowing the subject some freedom of motion. The motion enables subject to be measured in the sitting position and move relatively freely with the PET during acquisition. The detector consists of a Gd₂ SiO₅ (GSO) block, a tapered light guide and a flat panel photomultiplier tube (FP-PMT). Two types of GSO are used for depth-of-interaction (DOI) separation allowing the use of a small ring diameter without resolution degradation. The tapered light guide allows the use of larger GSO blocks with fewer FP-PMTs. Sixteen detector blocks are arranged in a 280 mm diameter ring. Transaxial and axial field-of-view (FOV) are 20 cm and 4.8 cm, respectively. Energy resolution of the block detectors was ~15% full width at half maximum (FWHM) and timing resolution was ~4.6 ns FWHM. Transaxial resolution and axial resolution at the center of the FOV were ~4.0 mm FWHM and ~3.5 mm FWHM, respectively. Sensitivity was 0.7% at the center of the axial FOV. Scatter fraction was ~0.6. Hoffman brain phantom images were successfully obtained. We conclude that the PET-Hat is a promising, low cost, small, wearable brain PET system for brain functional studies.