Slab-by-slab blurring model for geometric point response correction and attenuation correction using iterative reconstruction algorithms

The distance-dependent geometric point response of a single photon emission computed tomographic (SPECT) system and the attenuation effect of photons passing through the object are modeled in an iterative OS-EM reconstruction algorithm to improve both the resolution and quantitative accuracy of the reconstructed images. In this paper, an efficient incremental slab-by-slab blurring model was introduced to speed up the reconstruction. A specified number of neighboring vertical slices are grouped into a slab. Slab-by-slab blurring, rather than slice-by-slice blurring, is performed to reduce the convolution times for both projector and backprojector which model the geometric point response of the system. The key advantage of this slab-by-slab blurring model over the slice-by-slice model is that the computational time can be significantly reduced while still maintaining the spatial resolution and quantitative accuracy of the reconstructed images. The application of this incremental slab-by-slab blurring model, incorporated with a model for attenuation, to the image reconstruction of patient SPECT data shows improved resolution and contrast over the images reconstructed without the corrections; it also shows much less computational time for the reconstruction than the slice-by-slice implementation.