A point response function (PRF) is estimated in SPECT. A 3D PRF is based on measured emissions from a point source at different distances from the detector. Rather than sampling every location in space, the 2D PRFs at a sub-set of distances are sampled. The 3D PRF is then modeled with a representative 2D PRF and a scale as a function of distance. For a given distance from the detector, the 2D PRF to be applied is formed by scaling the representative 2D PRF using the scale for that distance.
Self-similar, transversely shift-invariant point response function in single photon emission computed tomography