Effects of detector sensitivity on image quality in multidetector SPECT

The common imaging practice of each detector acquiring projection data over a limited angle on multidetector systems introduces the possibility of imbalances in system response causing artifacts and changes in image quality. Here we evaluate the effect of variations in detector sensitivity caused by differences in the photopeak window position, width, and different collimators on reconstructed image quality. Analytical simulations of cardiac phantom geometries and experimental measurements with Data Spectrum's Cardiac and Deluxe SPECT phantoms on a 3 gamma camera SPECT system were used in the evaluation. The relative efficiency of one of three detectors was changed over a series of values between 100 and 0%, while the efficiency of the remaining two detectors was maintained at 100%. The results show decreased activity occurs in two 600 wide regions adjacent the path covered by the detector with the lower counting efficiency. The relative count ratios in the regions with decreased activity change over the range of 1.0 to 0.59 as the detector sensitivity is varied from 100 to 0% of the full energy window. The results show that variations in detector sensitivity can degrade spatial resolution and uniformity and create artifacts in reconstructed tomographic slices.