[Gate-users] No comptonPhantom or RayleighPhantom entries for voxelized phantom

Thu Mar 6 14:02:34 CET 2014

Hi Tom,
which version of GATE are you using? I had my problems with early versions of GATE 6 (like 6.0 or 6.1), and I have managed to get seemingly correct values with GATE 6.2.

First, I recall that for Rayleigh (not Compton) interactions, there was a bug in GATE 6.0 and 6.1 that was fixed in 6.2. In 6.0 and 6.1, an interaction from a "PenelopeRayleighScattering" (6.0/6.1) or "RayleighScattering" (6.1) process would not be counted as a Rayleigh interaction in the ROOT output since the code checks for a process name with "LowEnRayleigh" in it - this is due to these lines here:
http://www.opengatecollaboration.org/lxr/source/6.0.0/source/digits_hits/src/GateAnalysis.cc#L278
http://www.opengatecollaboration.org/lxr/source/6.1.0/source/digits_hits/src/GateAnalysis.cc#L281

Here, is it fixed:
http://www.opengatecollaboration.org/lxr/source/6.2.0/source/digits_hits/src/GateAnalysis.cc#L292

Here are some physics processes which could have been affected by that bug:
http://www.opengatecollaboration.org/lxr/source/6.0.0/source/physics/src/GateRayleighPenelopePB.cc
http://www.opengatecollaboration.org/lxr/source/6.1.0/source/physics/src/GateRayleighPenelopePB.cc
http://www.opengatecollaboration.org/lxr/source/6.1.0/source/physics/src/GateRayleighPB.cc

If you are already using GATE 6.2, the problem (or at least one solution) might be that you can attach the PhantomSD to the subvolumes which are created from your voxelized phantom. My current code contains this:

/gate/patientAT_AG_SI1_31/attachPhantomSD
[..., 4 more]
/gate/patientAT_AG_SI5_36/attachPhantomSD
/gate/patientAir_0/attachPhantomSD
/gate/patientAir_1/attachPhantomSD
/gate/patientConnectiveTissue_40/attachPhantomSD
/gate/patientLung_10/attachPhantomSD
[..., 27 more]
/gate/patientLung_9/attachPhantomSD
/gate/patientMarrow_Bone01_41/attachPhantomSD
[..., 13 more]
/gate/patientMarrow_Bone08_55/attachPhantomSD
/gate/patientSoftTissus_37/attachPhantomSD
/gate/patientSoftTissus_38/attachPhantomSD
/gate/patientSoftTissus_39/attachPhantomSD
/gate/patientworldDefaultAir/attachPhantomSD

The complete list depends on your phantom - you should include all subvolumes, but you may only include existing ones. I think the list of volumes generated is part of the GATE output, so you can grab this from your current simulation, prepend "/gate/patient" (or whatever your generating volume name is), append "/attachPhantomSD" and save this as the phantomSD.mac specific to that voxelized input and the volume-generation parameters. Should any of these change without yout re-generating the mac file, in the best case you lose one of the volumes you had in your the mac file before and your script returns an error message. In the worst case, you will get inaccurate results without noticing, for example, when only additional volumes are generated and you miss scatter interactions in those without getting any error message.

Best regards

Yannick

From: Tom Buitenhuis [mailto:h.j.t.buitenhuis at rug.nl]
Sent: Thursday, March 06, 2014 12:27 PM
To: Berker, Yannick; gate-users at lists.opengatecollaboration.org
Subject: No comptonPhantom or RayleighPhantom entries for voxelized phantom

Dear GATE users,

I am having the same problem as Yannick Berker described on 2011-10-21. I use the ImageNestedParametrisedVolume phantom for a PET simulation. The sources are described using interfiles. Everything seems to be working correctly, i.e. the sources and phantom are in the right place and coincidences are detected. The effect of phantom attenuation is also clearly visible.

The problem that I'm having, is that in the ROOT coincidences tree there is no comptonPhantom and RayleighPhantom data. I cannot add the VoxelPhantomSD to the ImageNestedParametrisedVolume, because I get an error message saying the command is unavailable. I can add the ordinary PhantomSD, but this does not seem to add the comptonPhantom or RayleighPhantom information to the coincidence tree. The comptonCrystal and RayleighCrystal entries are correct, so I think the physics processes are registered and working correctly.

I need the comptonPhantom and RayleighPhantom information to get scatter information on coincidences.

Did anyone else come across this problem, and if so, how did you solve it? Or can anyone point me in the direction of a solution?

Regards,

Tom Buitenhuis

PhD student
KVI - Center for Advanced Radiation Technology
University of Groningen
The Netherlands

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/HounsfieldMaterialGenerator/Generate

/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<http://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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