  Positional single photon incidence response (P-SPIR) theory is researched in
this paper to generate more accurate PSF-contained system matrix simply and
quickly. The method has been proved highly effective to improve the spatial
resolution by applying to the Eplus-260 primate PET designed by the Institute
of High Energy Physics of the Chinese Academy of Sciences(IHEP).
Simultaneously, to meet the clinical needs, GPU acceleration is put to use.
Basically, P-SPIR theory takes both incidence angle and incidence position by
crystal subdivision instead of only incidence angle into consideration based on
Geant4 Application for Emission Tomography (GATE). The simulation conforms to
the actual response distribution and can be completed rapidly within less than
1s. Furthermore,two-block penetration and normalization of the response
probability are raised to fit the reality. With PSF obtained, the
homogenization model is analyzed to calculate the spread distribution of bins
within a few minutes for system matrix generation. As a reult, The images
reconstructed indicate that the P-SPIR method can effectively inhibit the depth
of interaction (DOI) effect especially in the field close to the edge of the
field of view (FOV). What is more, the method can be promoted to any other PET
and the list-mode organization structure high-speedily and efficiently, which
substantially reduces the computing cost and ensures the accuracy of system
matrix for PET reconstruction.
