Geant4 Version: _geant4-10-06-patch-03 (6-November-2020)
Operating System: LInux
Compiler/Version: gcc (Ubuntu 7.5.0-6ubuntu2) 7.5.0
CMake Version: 3.29.1
Dear all,
I am a user of Gate. I am currently conducting a simulation of Y-90 bremsstrahlung SPECT imaging. In simulation, I used the FastY90 source, set up the GE Discovery NM 670 SPECT and MEGP collimator according to Exercise 6: SPECT imaging in Exercises for GATE. The FastY90 source was placed in a cylindrical water phantom. However, I have some questions in the setting of the physical process. In the physical process setup, is it sufficient to configure the physical processes only through the command “/gate/physics/addPhysicsList emstandard_opt3” (Method 1), or do we need to add the emstandard_opt3 physical process list and then add each of the physical processes that need to be simulated one by one, as shown in the following code (Method 1)? I have tried both of the above two methods for setting up the physical processes, and the resulting simulated projection results are quite different. The corresponding simulated projection outcomes from each method are presented below.
/gate/physics/addPhysicsList emstandard_opt3
#/gate/physics/addProcess RadioactiveDecay
#/gate/physics/addProcess Bremsstrahlung
#/gate/physics/processes/Bremsstrahlung/setModel StandardModel e-
/gate/physics/addProcess PhotoElectric gamma
/gate/physics/processes/PhotoElectric/setModel StandardModel
/gate/physics/addProcess Compton
/gate/physics/processes/Compton/setModel PenelopeModel
/gate/physics/addProcess RayleighScattering
/gate/physics/processes/RayleighScattering/setModel PenelopeModel
/gate/physics/addProcess GammaConversion
/gate/physics/processes/GammaConversion/setModel StandardModel
/gate/physics/addProcess NuclearResonanceScattering
The simulated projection results:
Method 1: Method 2:
Looking forward to your reply and help. Thank you very much!
Chenyu Yan