Theoretical determination of the collimator geometrical transfer function for the reconstruction of SPECT data

Iterative SPECT reconstruction algorithms allow for the inclusion of information related to the geometric system response with accuracy and flexibility. Since the experimental setup of a camera-collimator system may vary considerably, it is necessary to fit the restoration potential of the algorithm to the actual acquisition conditions. In order to avoid any experimental procedure, the authors developed a method to calculate weighting factors from the theoretical knowledge of the geometric system response of a multihole collimator. The calculation of the weighting factors was based on an appropriate discretization of the Radon transform whose kernel was modified to describe the variable system response of the collimator.