Iterative list mode reconstruction for coincidence data of gamma camera

The 3D acquisition data from positron coincidence detection on a gamma camera, can be stored in list-mode or histogram format. The standard processing of the list mode-data is Single Slice Rebinning (with a maximum acceptance angle) to 2D histogrammed projections followed by Ordered Subsets Expectation Maximization reconstruction. This method has several disadvantages: sampling accuracy is lost by histogramming events, axial resolution degrades with increasing distance from the center of rotation and useful events, with angle bigger than the acceptance angle, are not included in the reconstruction. Therefore an iterative reconstruction algorithm, operating directly on list-mode data, has been implemented. The 2D and 3D version of this iterative list-mode algorithm have been compared with the aforementioned standard reconstruction method. A higher number of events is used in the reconstruction, which results in a lower standard deviation. Resolution is fairly constant over the Field of View. The use of a fast projector and backprojector reduces the reconstruction time to clinical acceptable times