PET image reconstruction using LOR-OSEM with a 3D spatially variant system matrix

• Published in: 2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC) pp. 3752 - 3758
• Main Authors: Wiant, D.B., Gersh, J.A., Bennett, M.C., Bourland, J.D.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.10.2009
• Subjects: Detectors; Electromagnetic scattering; Geometry; Image reconstruction; Jacobian matrices; Particle scattering; Positron emission tomography; Reconstruction algorithms; Samarium; Spatial resolution
• ISBN: 9781424439614; 1424439612
• ISSN: 1082-3654; 2577-0829
• DOI: 10.1109/NSSMIC.2009.5401881

A point source was used to sample the point spread function (PSF) at over 6000 locations within the field of view (FOV) of a General Electric Discovery ST PET scanner (DST) in 2D high sensitivity acquisition mode. These measurements were used to optimize the derivation of a system matrix for the DST. We found for 2D acquisition mode that a system matrix using a PSF with radial, depth, axial, and azimuthal dependence produced reconstructed images with greatly improved spatial resolution and contrast-noise ratios over the entire FOV, as compared to the use of a geometrically derived system matrix. The main improvements in resolution and contrast-noise resulted from the inclusion of depth dependence in the model, which accounts for large variations in sensitivity in the DST that are due to the septa and a span of 11 present in 2D acquisition. Finally, we determined that exploitation of symmetries, particularly along the axial dimension, allow a system matrix of similar quality to what we achieved with over 6000 samples to be created with just over 1000 samples, i.e. with an almost 80% reduction in sample size.