Projection data registration for gated cardiac SPECT reconstruction

In a gated SPECT study, it is sometimes necessary to reconstruct an image for each time-frame. Because of cardiac beating and respiratory motion, the images from different timeframes are different. Each time-frame is very short. Due to the fact that the gamma photons acquired during each time-frame are limited, the reconstructed "low-count" images for each timeframe are very noisy. If we sum the projection data from all projections, the associated "high-count" reconstruction is less noisy, but we can only get one stationary image instead of a series of dynamic images. The objective of this paper is to wisely sum the projection data front the entire gated SPECT scan. Different summation strategy is used for different projection views and for different time-frames. As a result, a "high-count" projection data set is estimated for each time-frame and a series or "high count" dynamic images can be reconstructed.