NEMA NU-04-based Performance Characteristics of the LabPET-8TM Small Animal PET Scanner

The objective of this study is to characterize the performance of the preclinical avalanche photodiode (APD)based LabPET-8TM subsystem of the fully integrated trimodality PET/SPECT/CT TriumphTM scanner using the NEMA NU 04 – 2008 protocol. The characterized performance parameters include the spatial resolution, sensitivity, scatter fraction, counts rate performance, and image quality characteristics. The PET system is fully digital using APD-based detector modules with highly integrated electronics. The detector assembly consists of phoswich pairs of LYSO and LGSO crystals with dimensions of 2×2×14 mm having 7.5 cm axial and 10 cm transverse field-ofview (FOV). The spatial resolution and sensitivity were measured using a small Na point source at different positions in the scanner’s FOV. The scatter fraction and count rate characteristics were measured using a mouseand rat-sized phantoms fitted with F line source. The overall imaging capabilities of the scanner were assessed using the NEMA image quality phantom and laboratory animal studies. The NEMAbased radial and tangential spatial resolution ranged from 1.7 mm at the center of the FOV to 2.59 mm at a radial offset of 2.5 cm and from 1.85 mm at the center of the FOV to 1.76 mm at a radial offset of 2.5 cm, respectively. Iterative reconstruction improved the spatial resolution to 0.84 mm at the center of the FOV. The total absolute system sensitivity is 12.74% for an energy window of 250–650 keV. For the mouse-sized phantom, the peak noise equivalent count rate (NECR) is 183 kcps at 2.07 MBq/cc whereas the peak true count rate is 320 kcps at 2.5 MBq/cc with a scatter fraction of 19%. The rat-sized phantom had a scatter fraction of 31%, with a peak NECR of 67 kcps at 0.23 MBq/cc and a peak true count rate of 186 kcps at 0.27 MBq/cc. The average activity concentration and percentage standard deviation (%STD) are 126.97 kBq/ml and 7%, respectively. The performance of the LabPET-8 scanner was characterized based on the NEMA NU 04 – 2008 standards. The all in all performance demonstrates that the LabPET-8 system is able to produce high quality and highly contrasted images in a reasonable time, and as such it is well suited for preclinical molecular imaging-based research.