Evaluation of a Hamamatsu TOF-PET detector module with 3.2-mm pitch LFS scintillators and a 256-channel SiPM array

Using time-of-flight (TOF) information in image reconstruction improves image signal-to-noise ratio and quantitative accuracy in positron emission tomography (PET). A new TOF-PET detector module with a 3.2 mm pitch lutetium fine silicate (LFS) scintillator array one-to-one coupled to a 16×16 (256-ch) silicon photomultiplier (SiPM) array was made commercially available (C13500 series, Hamamatsu Photonics K.K.). In this study, as a candidate detector module for the next generation brain-dedicated PET, we changed the scintillator length of 20 mm to 10 mm according to our helmet-type PET geometry and investigated the basic performance of the PET detector module, including its energy resolution, sensitivity, coincidence response function (CRF) and coincidence timing resolution (CTR). All performance values were compared with those of the 4.2 mm pitch 144-ch detector module which was selected for our current helmet-type PET prototype. The energy resolution was 12% at 511 keV. The sensitivity was about 10% lower compared with those of the 4.2 mm pitch module. The average full width at half maximum (FWHM) of the CRFs was 1.9 mm. The CTRs had values of 235–241 ps with various energy windows after applying timing calibration. The CTR was not significantly changed (