[Gate-users] compton scatter problems

[anwen long]

Hi:
   I simulated a PET scanner based on block detector, in the simulation,
energy resolution was 30% @511keV and energy window was [150,750].  I picked
up the energy of inter-detector scatters, and a strange phenomenon was
found, the energy spectrum of inter-detector scatter has two peaks with one
of the peak is about 255keV, and another is about 511keV (attached figure
1). I added the energy of scatters origining from one gamma ray (attached
figure 2),  and found that some energy was beyond the upthreshold of energy
window, e.g. 750keV, and an energy peak appeared at about 750keV.
   What will cause this phenomenon?




  A.Long
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