COMPARISON OF FREQUENCY-DISTANCE RELATIONSHIP AND GAUSSIAN-DIFFUSION-BASED METHODS OF COMPENSATION FOR DISTANCE-DEPENDENT SPATIAL-RESOLUTION IN SPECT IMAGING

The goal of this investigation was to compare resolution recovery vers us noise level of two methods for compensation of distance-dependent r esolution (DDR) in SPECT imaging. The two methods of compensation were restoration filtering based on the frequency-distance relationship (F DR) prior to iterative reconstruction, and modelling DDR in the projec tor/backprojector pair employed in iterative reconstruction. FDR resto ration filtering was computationally faster than modelling the detecto r response in iterative reconstruction. Using Gaussian diffusion to mo del the detector response in iterative reconstruction sped up the proc ess by a factor of 2.5 over frequency domain filtering in the projecto r/backprojector pair. Gaussian diffusion modelling resulted in a bette r resolution versus noise tradeoff than either FDR restoration filteri ng or solely modelling attenuation in the projector/backprojector pair of iterative reconstruction. For the pixel size investigated herein ( 0.317 cm), accounting for DDR in the projector/backprojector pair by G aussian diffusion, or by applying a blurring function based on the dis tance from the face of the collimator at each distance, resulted in ve ry similar resolution recovery and slice noise level.