Initial imaging results from a high spatial-resolution time-of-flight PET detector designed for dedicated breast imaging

This paper discusses initial imaging results from a high-resolution time-of-flight detector specifically developed for a limited-angle dedicated breast PET scanner. To maintain high spatial-resolution and sensitivity, the detector design consists of 32 × 32 array of 1.5 × 1.5 × 15 mm³ LYSO crystals coupled to a single Hamamatsu H8500 multi-anode photomultiplier tube with a modified high-voltage divider circuit. To minimize the number of readout channels, compact front-end electronics that summed anode-signals along each of the orthogonal directions was also developed. Experimental performance evaluation of a complete detector-module demonstrates excellent energy, timing resolution and clear discrimination of most crystals. An average energy resolution of about 12.7% FWHM and an average coincidence timing resolution of 348 ps for two such detectors was measured. The dedicated breast PET scanner comprises of two parallel detector heads, each 15 cm by 10 cm and comprised of two rows of three detector-modules. We also experimentally evaluated the imaging capability of the scanner design via an experimental benchtop-demonstrator consisting of two fully assembled detector-modules on opposing translational stages. Imaging experiments with a hot lesion phantom that had an 8-mm diameter lesion with 8:1 activity uptake ratio, successfully demonstrate the capability of the system in imaging small lesions in a uniform background.