A practical projector-backprojector modeling attenuation, detector response, and scatter for accurate scatter compensation in SPECT

A projector-backprojector pair that models attenuation and the spatially variant geometric and the scatter response functions in a uniformly attenuating object for single photon emission computed tomography (SPECT) was developed. The scatter response function (SRF) is modeled using a scheme based on the scatter responses of point sources in large slab phantoms. This scheme, slab derived scatter estimation, allows efficient and accurate modeling of the asymmetric properties of the scatter response during the projection and backprojection operations. The scatter model was verified by comparison of scatter line source response functions and scatter primary ratios obtained from direct Monte Carlo simulations. This eliminates the need for extensive Monte Carlo calculations for each object or extremely large memory to store the resulting SRFs for every pixel and view. Combined with iterative reconstruction techniques, this projector-backprojector provides a practical and accurate means for scatter compensation in SPECT.<>