[Evaluation of the performance of a gamma camera equipped with a 5/8" versus 1" thick NaI detector]

The upgrade of a gamma camera from a 5/8" to a 1" thick crystal, the latter with StarBrite technology, prompted to the investigation of changes in performance parameters for planar scintigraphy and SPECT as well as for PET in coincidence mode. For planar and SPECT parameters, the performance was measured according to NEMA Standard Protocol NU1-2001. No changes were found in terms of intrinsic uniformity, intrinsic spatial resolution, linearity, energy resolution, system resolution, and tomographic system resolution. The only change was an increase of system sensitivity for higher energy gamma rays. For the PET scanner in coincidence mode, the image quality of the camera was determined according to NEMA NU2-2001. Visually and in terms of contrast values there was a significant improvement of image quality. Changes in image quality relevant for clinical use were tested by evaluation of planar patient scans acquired within a short time with two gamma cameras of the same type, different only in crystal thickness (5/8" and 1"). No statistically significant difference was found between corresponding scans. For planar and SPECT imaging, the gamma camera with 1" thick detector and StarBrite technology demonstrated the same performance of a camera with a 5/8" crystal. For PET in coincidence mode the new detector proved clearly superior.