ComptonRec: Mastering conic sections for a direct 3D compton image reconstruction

Given the complexity of the image reconstruction procedures for Compton Camera events, especially when a 3D image is required for distributed sources in space, a simple, direct algorithmic approach is presented in this work. The developed ComptonRec package carefully handles the geometry of the conic sections to accumulate ray density distribution in a user defined voxelized volume inside the specified field of interest. Prior to planar reconstruction, the event selection part of the program filters out misidentified coincidence events and other physical background events with unbalanced total energy or inverse interaction sequence with the camera's subsystems. For each accepted event a series of planar reconstructions is performed, where the density distribution is the accumulation product of the conic intersection with all the affected pixels. A 3D image is finally reconstructed by assembling the partial planar information and by taking into account volume effects. The efficiency of this reconstruction method is checked with a plethora of simulated phantoms and results are presented and discussed.