[Gate-users] Potential bug in units to materials conversion

[Matthew Strugari]

Hi everyone,

As a followup to my previous email, it appears that the bug affects voxelized simulation results. After allowing the simulation to run to completion, the dose distribution due to 40 million Y-90 primaries does not show any back-scatter effects at the air-water interface. I have attached an image which highlights a couple regions showing the extension of dose into "air". The dose decreases smoothly with distance from the source despite crossing the boundary.

I use the following lines to define my voxelized phantom:
/gate/world/daughters/name                                  phantom
/gate/world/daughters/insert                                ImageNestedParametrisedVolume
/gate/phantom/geometry/setImage                             data/Cropped_kidneyContour_binary.mhd
/gate/phantom/geometry/TranslateTheImageAtThisIsoCenter     0 0 0 mm
/gate/phantom/geometry/setRangeToMaterialFile               data/KidneyAttenuationRange.dat

I have also changed the attenuation range to overlap with values near 0 and 1 in case of any floating point errors to no avail. If anyone sees any mistakes in my phantom definition or has encountered similar issues, please let me know. I am not sure what to do about this.

Regards,
Matthew

________________________________
From: Gate-users <gate-users-bounces at lists.opengatecollaboration.org> on behalf of Matthew Strugari <matthew.strugari at dal.ca>
Sent: February 28, 2020 12:43 PM
To: gate-users at lists.opengatecollaboration.org <gate-users at lists.opengatecollaboration.org>
Subject: [Gate-users] Potential bug in units to materials conversion

Dear gate-users,

There appears to be an issue when defining the associated material for each voxel in an image. I have loaded a binary image with the units to materials conversion defined in a AttenuationRange.dat file:
2
0 0 worldDefaultAir
1 1 Water
I have also set the world material as worldDefaultAir resulting in a total of two defined materials throughout my entire simulation. When executing my macro, there is a message stating that 3 materials are in the image:
[Volume-1]  Number of different materials in the image data/Cropped_contour_binary.mhd : 3
[Physic-1]
[Physic-1]  ----------------------------------------------------------
[Physic-1]                      Ionization potential
[Physic-1]   - worldDefaultAir defaut value: I = 85.7031 eV
[Physic-1]   - Air defaut value: I = 85.6694 eV
[Physic-1]   - Water defaut value: I = 68.9984 eV
[Physic-1]  ----------------------------------------------------------
Has anyone else noticed this issue? I don't know if it's possible to verify what voxels are assigned to what material. It would be nice to see the total number of voxels assigned to a given material at run time.

Best,

Matthew


--

Matthew Strugari

Biomedical Translational Imaging Centre - BIOTIC,
5890 University Ave,
Halifax, NS, B3K 6R8
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