[Gate-users] differences in energy spectra from different GATE releases

[Melanie Hohberg]

Dear GATE-users,

In our simulations, we have observed that for the singles and the
coincidences, the energy spectrum does not fall to zero in the newest
version of GATE (3.1.2). For identical simulations using GATE version
3.0.0, we do not see this effect and the energy spectra falls to zero as
expected. This problem has been seen in simulations of MADPETII (small
animal PET scanner) and in ECAT from the GATE example.

In both the old and new versions of GATE, the benchmark PET was
successfully completed and no difference in the energy spectra was
observed. However, the upper energy threshold of the benchmark is set to
650keV while our simulations are performed at higher upper energy
thresholds.

We are attaching plots of the energy spectra from the same
simulation for the singles and coincidences. It is evident that the energy
spectra are different depending on the GATE version used (3.1.2 versus
3.0.0). This puzzling result is independent on the computer on which the
simulation is run. Below are listed the energy resolution and energy
threshold of the simulation:

#      E N E R G Y   B L U R R I N G
/gate/digitizer/Singles/insert blurring
/gate/digitizer/Singles/blurring/setResolution 0.0
/gate/digitizer/Singles/blurring/setEnergyOfReference 511. keV

#       E N E R G Y   C U T
/gate/digitizer/Singles/insert thresholder
/gate/digitizer/Singles/thresholder/setThreshold 250. keV
/gate/digitizer/Singles/insert upholder
/gate/digitizer/Singles/upholder/setUphold 950. keV

We would be grateful if anyone could explain why this problem occurs
and how we may resolve it.

Thanks in advance,

Irene Torres and Jasmine Schirmer

PS: Sorry, we have to use the email account of Melanie, one of our colleagues, because we have some problems with our gate subscription

PS2: In the .tgz attached file there are the spectra for the coincidences, we could not send the spectra for the singles (size limit), if anyone is interested we can send them

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