LMIRA: list mode iterative reconstruction algorithm for SPECT

The goal of this project is to investigate a new method for using list-mode data instead of binned projection data for SPECT reconstruction. List-mode acquisition was once standardly available for planar scintigraphy, and is now becoming available for SPECT acquisition. The authors implemented maximum likelihood iterative reconstruction with list-mode data for SPECT using a projector/backprojector pair which employ an intermediate stage to separate the source and camera specific components. The algorithm uses the emission radiance distribution, calculated from the estimated source distribution, to obtain the probabilities used in the iterative reconstruction method. The model takes into account distance-dependent resolution and non-uniform attenuation. Results illustrate how the individual steps of the algorithm work. LMIRA (List-Mode Iterative Reconstruction Algorithm) is compared to the standard MLEM iterative reconstruction method which employs binned data. The authors conclude that the finer sampling provided by list-mode data, and the noise characteristics of list-mode reconstruction result in superior image quality. In further research they plan to investigate the inclusion of the intrinsic spatial resolution, the energy resolution, and the modeling of scatter in LMIRA