Performance of a prototype brain PET scanner based on semiconductor detectors

486 Objectives: The first prototype brain PET scanner using semiconductor detectors has been developed to achieve high spatial resolution and reduced scatter fraction. To confirm feasibility of the scanner, performance measurements were conducted using the NEMA NU2-2001 and NU2-1994 procedures. Phantom and brain PET images were also measured to evaluate applicability to clinical use. Methods: The scanner has a patient port diameter of 35 cm and an axial field of view of 25 cm without interplane septa. It comprises of 18 detector units arranged around the patient port. Each detector unit has 22 detector boards arranged along axial filed of view. The detector board has CdTe detectors on each side. Signals are read by 3-layer DOI (Depth Of Interaction) and processed with the “individual channel readout” technology. Physical performances, such as spatial resolution, sensitivity and noise equivalent count rates (NECR) were measured with NEMA standards. Results: The transverse and axial resolutions near the center are 2.3 mm and 5.1 mm, respectively. The absolute sensitivity and the scatter fraction evaluated with NEMA NU2-1994 phantom are 18cps/Bq/cc and 23% respectively. These estimates are for a lower energy threshold of 450keV. NEC2R are 41kcps at 7.4 kBq/cc. Images from the hot rod phantom as well as FDG volunteer’s scans show high spatial resolution capability. Conclusions: The first prototype brain PET scanner using CdTe detectors was developed and its performance was evaluated using NEMA standards. The results show that the PET scanner is feasible for clinical use with high spatial resolution. The semiconductor detectors have good energy resolution which leads to minimum scatter fraction in 3D imaging.