A STUDY OF RECONSTRUCTION ACCURACY FOR A CARDIAC SPECT SYSTEM WITH MULTI-SEGMENTAL COLLIMATION

To improve the geometric efficiency of cardiac SPECT imaging, we previ ously proposed to use a multi-segmental collimation with a cylindrical geometry. The proposed collimator consists of multiple parallel-hole collimators with most of the segments directed toward a small central region, where the patient's heart should be positioned. This technique provides a significantly increased detection efficiency for the centr al region, but at the expense of reduced efficiency for the surroundin g region. We have used computer simulations to evaluate the implicatio n of this technique on the accuracy of the reconstructed cardiac image s. Two imaging situations were simulated: 1) the heart well placed ins ide the central region, and 2) the heart shifted and partially outside the central region. A neighboring high-uptake liver was simulated for both imaging situations. The images were reconstructed and corrected for attenuation with ML-EM and OS-EM methods using a complete attenuat ion map. The results indicate that errors caused by projection truncat ion are not significant and are not strongly dependent on the activity of the liver when the heart is well positioned within the central reg ion. When the heart is partially outside the central region, hybrid em ission data (a combination of high-count projections from the central region and low-count projections from the background region) can be us ed to restore the activity of the truncated section of the myocardium. However, the variance of the image in the section of the myocardium o utside the central region is increased by 2-3 times when 10% of the co llimator segments are used to image the background region.