A small gamma camera combined with a uniformly redundant array (URA) collimator: the performance evaluation using detective quantum efficiency (DQE)

The gamma scintillation camera systems are recently used in various industrial, environmental and medical diagnostic fields. Moreover, the portable use in various fields is possible using miniaturized gamma camera systems. The necessity of objective and quantitative factors for the performance evaluation of gamma camera systems increase as the usefulness of these systems increase. The detective quantum efficiency(DQE), which is already applied to the performance evaluation of X-ray imaging systems, was partially revised and applied to our gamma camera system. In this study, our gamma camera system consisted of a scintillation crystal, a PSPMT with 5-inch diameter and read-out electronics. The four collimators, three pinhole collimators with different pinhole diameters and a coded-aperture collimator using uniformly redundant array (URA), were manufactured for imaging experiments. In the result, the spatial resolution slightly decrease as pinhole diameter increase because of thick scintillation material for high energy photons detection. The normalized noise power spectra obviously decrease as pinhole diameter increase because of signal to noise ratio. Finally, the DQE increase as pinhole diameter increase. The highest DQE was presented by the URA collimator. In spite of slightly low spatial resolution, URA present highest performance because of very low noise power. Our results present interrelation with conventional evaluating factors, for example, FWHM and uniformity. We found that DQE can be effectively used to evaluate imaging performance of gamma camera systems.