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 tomography (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. A specified number of neighboring vertical slices are grouped into a slab, and an efficient incremental slab-by-slab blurring model is introduced to accelerate the reconstruction. The advantage of the slab-by-slab blurring model over the slice-by-slice model is that the computational time is reduced, while still maintaining the spatial resolution and quantitative accuracy of the reconstructed images. The application of this incremental slab-by-slab blurring model with a slice-by-slice attenuation model to the image reconstruction of phantom, Monte Carlo simulated SPECT data, and patient data shows improved resolution and contrast over the images reconstructed without the corrections. The reconstruction is accelerated by a factor of about 1.4, and the projection/backprojection operation is accelerated by a factor of about 5, using the slab-by-slab convolution implementation with 8 slices in a slab compared with the slice-by-slice convolution implementation.