Performance evaluation of siemens CTI ECAT EXACT 47 PET scanner using NEMA NU2-2001

In this study, system performance of Siemens CTI ECAT EXACT 47 PET scanner was measured using NEMA NU2-2001 standard. ECAT EXACT 47 is a BGO crystal based PET scanner. Coincidence window are set to 12 ns, and energy window are set to 250 similar to 650 keV. For the spatial resolution measurement, F-18 point source was placed at 1cm and 10 cm offset from the center of transaxial FOV. Images were reconstructed using FBP with ramp filter. To measure the system sensitivity, NEMA sensitivity phantom filled with F-18 solution and surrounded by 1 similar to 5 aluminum sleeves were scanned at the center of transaxial FOV and 10 cm offset from the center. Attenuation free values of sensitivity were estimated by extrapolating data to the zero wall thickness. NEMA scatter phantom with length of 70 cm was filled with F-18 solution (2D: 2,900 MBq), and coincidence count rates were measured for 7 half-lives to obtain noise equivalent count rate (NECR) and scatter fraction. Transverse and axial resolutions at 1cm offset from the center were 9.1 and 9.8 mm (FBP, 2D and 3D), Sensitivity values were 709 (2D), 3332 (3D) cps/MBq at the center and 796(2D), 4050 (3D) cps/MBq at 10 cm offset from the center. Scatter fractions were 0.19 (2D). Peak true count rate and NECR were 64.0 kcps@37.5 kBq/mL and 49.6 kcps@37.5 kBq/mL in 2D. Information about the performance of EXACT 47 PET scanner reported in this study will be useful for the quantitative analysis of data and determination of optimal image acquisition protocols using this widely used scanner for clinical and research purposes.