Studies of quality control data under NEMA NU1-2001 to evaluate the performance of gamma camera

Objective : To show the application of data from the quality control and preventive maintenance under NEMA NU1-2001 for the practical performance evaluation of gamma camera. Method: The study was divided into two parts: (1) the quality control data for gamma camera performances based on measurement of Intrinsic flood field Uniformity (IU), Intrinsic Energy Resolution (IER) and Peak Position (PP) on a weekly basis from January 2005 to March 2013 were to be retrospectively evaluated; (2) the current performances covering 14 parameters of the 5 specifications were to compare with the reference values certified by the manufacturer. Results : In the first part, the mean±3SD (99.73% confidence interval) of the mean IU adjusted to the dimension of Central Field Of View (CFOV) for Detector 1 and Detector 2, were 2.66±1.27% and 2.54±1.27% respectively, with a trend to slightly increases each year. For the detector resolution, Detector 1 and Detector 2 exhibited IER of 9.23±0.32% and 9.38±0.25% respectively. The long-term resolution trends after the first service of both detectors were not significantly deviated when compared to the present data. For the last parameter, the mean PP for Detector 1 and Detector 2 were 139.31±0.76 and 139.30±0.61 keV respectively. They were absolutely identical. The percentage differences of the PP were negligible when compared to year of installation. In the second part, under NEMA NU1-2001, the current performance data of Specification 1, IER of both detectors of 9.10% and 9.30% were better than the reference values of 9.8%. Specification 2, PP of both detectors was within an acceptable limit. Specification 3 of both detectors passed 4 parameters of the Intrinsic Spatial Resolution reference values. Specification 4, Intrinsic Uniformity of both detectors also passed all criteria of the 4 parameters. The last specification, Intrinsic Spatial Linearity values of both detectors was superior to the reference values. Conclusion: Regarding to the evaluation of the gamma camera performance under NEMA NU1-2001 after 8-year service and a preventive maintenance, three specifications of weekly QC have passed the regulations of performance tests within 99.73% confidence interval. Consequently, they can be used in the practical performance evaluation of gamma camera. Bull Chiang Mai Assoc Med Sci 2013; 46(3): 215-231