PET reconstruction with system matrix derived from point source measurements

The quality of images reconstructed by statistical iterative methods depends on an accurate model of the relationship between image space and projection space through the system matrix. The elements of a system matrix on the HiRez scanner from CPS Innovations were acquired by positioning a point source at different positions in the scanner field of view. Then, a whole system matrix was derived by processing the responses in projection space. Such responses included both geometrical and detection physics components of the system matrix. The response was parameterized to correct for point source location, smooth projection noise and the whole system matrix was derived. The model accounts for axial compression (span) used on the scanner. The projection operator for iterative reconstruction was constructed using the estimated response parameters. Computer-generated and acquired data were used to compare reconstruction obtained by the HiRez standard software and that produced by better modeling. Results showed that better resolution and noise property can be achieved with the modeled system matrix.