A New method to calculate Energy Resolution based upon NEC phantom

Energy resolution is an important parameter which affects the capability of scanner to distinguish scatter counts from trues count. A better energy resolution can reduce the amount of scatter in the acquired data. In this article we propose a new method to measure energy resolution using the NEMA NEC phantom. This method is evaluated by comparing the energy resolution obtained from proposed method with that obtained using a line-source in air at 45 mm offset from the center of scan FOV. The measurements are performed on Siemens next generation PET/CT SiPM PET/CT and Biography mCT scanners. For Biograph mCT scanner, at low count rate, energy resolution of 12.2% was obtained using line-source in air and 12.1% was obtained using line-source in NEC phantom. For prototype SiPM scanner, at low count rate, energy resolution of 9.4 % was obtained using both methods. At low to moderate count rates, an energy resolution using line-source in NEC phantom after proper corrections, and line-source in air are similar.