Development of a TOF detector for brain PET

Summary form only given. A positron emission tomography (PET) detector for neuro-imaging is required to have high signal-to-noise ratio (SNR) as well as high spatial resolution. Time-of-flight (TOF) information can improve SNR of PET by localizing a positron annihilation point. The purpose of this study is to develop a TOF detector for brain PET having spatial resolution ≤ 2 mm and CTR ≤ 330 ps. PET detector module consisted of a 6 × 6 array of LYSO scintillators and a 4 × 4 array of 3 × 3 mm² MPPCs. The cross-sectional area of the individual scintillators was chosen to have 2 × 2 mm² to obtain high spatial resolution. The length of the scintillator (20 mm) was designed to reduce the light propagation delay for TOF while maintaining high stopping power for 511 keV gamma-rays. Capacitive charge division (CCD) network was used to identify the position of gamma event. Because the rise time of its outputs is not severely degraded compared with that of individual anode outputs, it has better timing performance than other multiplexing methods such as resistive charge division method. In the CCD network, anodes of the MPPC array were connected to capacitors having different capacitances according to their position. The flood histogram of the detector module was successfully obtained and all LYSO crystals in the detector module were clearly identified. The average energy resolution of the detector module at 511 keV was 15.4 ± 0.9%. The best CTR of the detector was 303 ± 14 ps FWHM allowing to achieve twice SNR gain compared to that of the standard PET.