Reducing the computational load of iterative SPECT reconstruction methods by preprocessing the projection data to compensate for nonstationary resolution and attenuation

By accurately modeling the physics of photon transport into the projection and backprojection operations, iterative SPECT reconstruction methods can reduce the degrading effects of scatter, attenuation and the non-stationary spatial resolution of the camera. Unfortunately, iterative reconstruction methods have required very long computation times, predominately due to the complexity involved in modeling these degrading effects into the projection and backprojection operations. In this study, we describe an approach which allows SPECT iterative reconstruction algorithms to be implemented with a reduction in the number of computations needed. The idea is to pre-process the measured projection data to compensate for scatter and attenuation, as well as to transform the projection data to those which would have been obtained with a stationary system resolution. Results of simulation studies indicate that preprocessing the measured projection data reduces the number of computations needed to perform the projection and backprojection operations, and yields reconstructions which differ minimally from those obtained using the slower standard iterative approach of modeling both photon attenuation and nonstationary blurring in the projection and backprojection steps.