ABSTRACT
Objective To propose a method for high-energy photon 3D decoding of PET detector to decode reactive crystal position and calculate γ ray depth in the scintillating crystal. Methods Light transmitting windows were set between the crystal arrays, visible photon groups were guided to distribute in the photoelectric sensor array during a single event, and sensor signal intensity was regulated to realize position and depth decoding of the high-energy photon.Monte Carlo method was used to compare the designs of different light transmitting windows to determine the effects of the crystal surface treatment mode on the results. Experiments were executed for further verification. Results The experimental results had consistency with simulation ones;the signal received through the reaction crystal was always stronger than that through the adjacent, which could decode the reaction crystals; the relations between the depth of interaction (DOI) and energy differences of the photo sensors were monotonic with the changes of DOI,and thus could be used to calculate the DOI;when using single window,the DOI vs.Diff.Energy curves had two segments which were not desired for DOI measurement;crystals with rough surfaces were more desired since the qualities of their DOI vs.Diff.Energy curves were better;the dual window method had the best DOI vs.Diff.Energy curves in term of linearity.Conclusion The method can realize 3D decoding of the discrete crystal array,which improves the energy resolution of the PET system. [Chinese Medical Equipment Journal, 2018,39(5):22-28,63]
ABSTRACT
The purpose of this study is to optimize a parallel-hole collimator for small gamma camera having the pixellated crystal array and evaluate the effect of crystal-collimator misalignment on the image quality using a simulation tool GATE (Geant4 Application for Tomographic Emission). The spatial resolution and sensitivity were measured for the various size of hexagonal-hole and matched square-hole collimators with a Tc-99m point source and the uniformity of flood image was estimated as a function of the angle between crystal array and collimator by misalignment. The results showed that the spatial resolution and sensitivity were greatly improved by using the matched collimator and the uniformity was reduced by crystal-collimator misalignment.