[Gate-users] Prloblems using HounsfieldMaterialGenerator

Berker, Yannick Yannick.Berker at philips.com
Fri Oct 21 11:54:55 CEST 2011

Dear GATE users,

I have some issues using the HounsfieldMaterialGenerator to simulate a PET scan of a patient. The simulation itself is running fine, but I am lacking two features that I am used to from other simulations, which are scatter information and color visualization. I mainly used the example from http://www.creatis.insa-lyon.fr/gate/Example2/ to generate the following phantom:

/gate/HounsfieldMaterialGenerator/SetMaterialTable                  CT/Schneider2000MaterialsTable.txt
/gate/HounsfieldMaterialGenerator/SetDensityTable                   CT/Schneider2000DensitiesTable.txt
/gate/HounsfieldMaterialGenerator/SetDensityTolerance               0.03 g/cm3
/gate/HounsfieldMaterialGenerator/SetOutputMaterialDatabaseFilename CT/p971-HUmaterials.db
/gate/HounsfieldMaterialGenerator/SetOutputHUMaterialFilename       CT/p971-HU2mat.txt
/gate/world/daughters/name                                          patient
/gate/world/daughters/insert                                        ImageRegionalizedVolume
/gate/geometry/setMaterialDatabase                                  CT/p971-HUmaterials.db
/gate/patient/geometry/SetHUToMaterialFile                          CT/p971-HU2mat.txt
/gate/patient/geometry/SetImage                                     CT/p971s3.hdr

The ROOT output shows me that the volume is placed correctly, and the distribution of detected coincidences also shows the effect of photon attenuation by the phantom. However, I cannot attach a VoxelPhantomSD to the patient - I receive an error message telling me that this command is unavailable:
[G4-cerr] ***** COMMAND NOT FOUND </gate/patient/attachVoxelPhantomSD> *****
Attaching an ordinary PhantomSD seems to work, but only generates 0 entries in ComptonPhantom and RayleighPhantom. I also tried using a ImageNestedParametrisedVolume, with no effect. ComptonCrystal entries, however, seem to be correct (>= 0).

Apart from that, how can I visualize the voxelized phantom using colors? I was not able to add color attributes (like "true 0.5 0.5 0.5 1.0") to p971-HU2mat.txt manually, since this resulted in the following error message:
src/GateVImageVolume.cc (l.332): No Hounsfield material defined in the file CT/p971s3_ToSim_OneBP_HU2mat_Colors.txt. Abort

Does anyone have knowledge in this area, or can point to some helpful documentation on this topic? The GATE User's Guide has a few, but only incomplete examples for the case of voxelized phantoms and sources.

Best regards,

Yannick Berker

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