title: Validation of the central-ray approximation for attenuated depth-dependent convolution in quantitative SPECT reconstruction.
abstract: In order to model photon attenuation and detector resolution variation as a depth-dependent convolution for efficient reconstruction of quantitative SPECT, a central-ray approximation is necessary. This work investigates the impact of the approximation upon reconstruction accuracy and computational efficiency. A patient chest CT image was acquired and converted into an object-specific attenuation map. From a segmentation of the map, an emission thorax phantom was constructed with a cardiac insert. To generate a system-specific resolution-variant kernal, a point source was measured at several depths from the surface of a low-energy, high-resolution, parallel-hole collimator of a SPECT system. Projections of parallel-beam geometry were simulated from the phantom, the map, and the kernel on an elliptical orbit. Reconstruction was performed by the ML-EM algorithm with and without the central-ray approximation. The approximation cuts down dramatically (more than 100 fold) the computing time with a negligible loss (less than 1%) of reconstruction accuracy.
authors.affiliation: Department of Radiology, Electrical Engineering, State University of New York, Stony Brook 11794, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Liang
authors.forename: J
authors.initials: J
authors.lastname: Cheng
authors.forename: J
authors.initials: J
authors.lastname: Ye
mesh_terms: D000465:Algorithms; D006801:Humans; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D017785:Photons; D013902:Radiography, Thoracic; D015203:Reproducibility of Results; D015899:Tomography, Emission-Computed, Single-Photon / Q000295:instrumentation / Q000379:methods*