Three-dimensional correction of experimentally determined gamma camera response

The response of a gamma camera depends on the source to-camera distance. It results in a two-dimensional blurring of the projection image and in an increasing loss in resolution with increasing distance from the face of the collimator. Here, the authors present a method for experimentally estimating a parametric model for the point source response of a gamma camera with parallel hole collimator. This model is used to incorporate the three-dimensional spatially varying camera response into the projection and back-projection operations of the tomographic reconstruction maximum likelihood algorithm which also compensates for the three-dimensional uniform attenuation. Using phantom experiments, the authors demonstrated a substantial improvement in the quality and the quantitative accuracy of the single photon emission computed tomography images