Fast shift-variant resolution compensation within iterative reconstruction for fan-beam collimator

In this paper we have modeled the spatially-varying resolution of a fan-beam collimator as a function of both distance and lateral position across the imaging plane within iterative reconstruction. We demonstrate that an incremental blurring technique can be used to more efficiently model such non-stationary resolution than the straightforward non-stationary convolution methodology with a gain of 1.5X in speed and 99% less memory usage. This method can therefore be used for efficient variable resolution compensation in 3D for collimator geometries in which the detector response function varies across the imaging plane as well as with distance from the face of the collimator.