Observed inter-camera variability of clinically relevant performance characteristics for Siemens Symbia? gamma cameras

Abstract

An evaluation of the inter-camera (i.e., between cameras) variability of clinically relevant performance characteristics for Symbia? gamma cameras (Siemens Medical Solutions, USA) was conducted based on measurements made using nine separate systems. The significance of the observed inter-camera variability was determined by comparing it to the intra-camera (i.e., within a single camera) variability. Measurements of performance characteristics were based on the NEMA standards and AAPM Reports No. 6, 9, 22 and 52. All of the measurements were performed using Tc-99m (except Co-57 for extrinsic resolution) and low-energy high-resolution collimation. Of the nine cameras, 4 have 3/8" and 5 have 5/8" thick crystals. Intrinsic energy resolution, intrinsic and extrinsic spatial resolution, intrinsic integral and differential flood uniformity over the useful field-of-view, count rate at 20% count loss, planar sensitivity, SPECT resolution, and SPECT integral uniformity were evaluated. The intra-camera variability was estimated by repeated measurements of the performance characteristics on a single system. The significance of the observed inter-camera variability was evaluated using the two-tailed F-distribution. The planar sensitivity of the gamma cameras tested was found be variable at the 99.8% confidence level for both the 3/8? and 5/8? crystal systems. The integral uniformity and energy resolution were found to be variable only for the 5/8? crystal systems at the 98% and 90% confidence level, respectively. All other performance characteristics tested exhibited no significant variability between the different camera systems. The measured variability reported here could perhaps be used to define nominal performance values of Symbia gamma cameras for planar and SPECT imaging.