[Gate-users] Voxelized XCAT source yields empty result

Ida Häggström ida.haggstrom at radfys.umu.se
Thu Sep 17 11:16:07 CEST 2009

Hello gaters!
I'm trying to incorporate a voxelized XCAT (formerly known as NCAT) source
into GATE and I'm having some difficulties. First of all, I'm using the
scanner from the benchmarkPET in the setup from "example_FULL_SIMULATION"
(without any phantom) and I've got my macro to work when I use a simple
source as the one below:
/gate/source/addSource twogamma
/gate/source/twogamma/setActivity 10. becquerel
/gate/source/twogamma/setType backtoback
/gate/source/twogamma/gps/particle gamma
/gate/source/twogamma/gps/energytype Mono
/gate/source/twogamma/gps/monoenergy 0.511 MeV
/gate/source/twogamma/gps/type Volume
/gate/source/twogamma/gps/shape Sphere
/gate/source/twogamma/gps/radius 0.25 mm
/gate/source/twogamma/gps/centre 0. 0. 0. mm
/gate/source/twogamma/gps/angtype iso

Now I've configured my own voxel source as:
# Declaration of the fact that a voxellized source will be used.
/gate/source/addSource xcat voxel

# Declaration that the voxellized source will be entered
# using image (ascii) data.
/gate/source/xcat/reader/insert image

# example for a linear translator: this scales all numbers
# directly into activities
/gate/source/xcat/imageReader/translator/insert linear
/gate/source/xcat/imageReader/linearTranslator/setScale 1. Bq

# The following line allows you to insert the ASCII file
# that contains all necessary numbers for all pixels
/gate/source/xcat/imageReader/readFile /xcat/image.dat

# The deafult position of the voxellized source is in the 1^{st}
# quarter. So the voxellized source has to be shifted over half its
# dimension in the negative direction on each axis
/gate/source/xcat/setPosition -130. -130. -300. mm

# The following lines characterize the size
# no difference with an analytical source
/gate/source/xcat/setType backtoback
/gate/source/xcat/gps/particle gamma
/gate/source/xcat/setForcedHalfLife 1222.8 s #Carbon-11
/gate/source/xcat/gps/energytype Mono
/gate/source/xcat/gps/monoenergy 511. keV
/gate/source/xcat/gps/angtype iso
/gate/source/xcat/gps/mintheta 90. deg
/gate/source/xcat/gps/maxtheta 90. deg
/gate/source/xcat/gps/minphi     0. deg
/gate/source/xcat/gps/maxphi   360. deg
/gate/source/xcat/gps/confine NULL

/gate/source/xcat/dump 1

The XCAT source is a 128x128x103 activity image of the torso, with voxel
sizes 0.625x0.625x0.625 mm. The file image.dat looks like:
128, 128, 103

I.e. voxel values ranging from 0 to 255. When I run my macro I don't get any
errors, but I don't see any photon tracks from the source, or any source at
all for that matter, in my openGL visualisation. I just see the camera. For
the simple source I see the source and gamma tracks for each frame... Also,
the output (RAW) records 0 singles, 0 coincidences etc, i.e. it's empty! I
wonder if it's a simple error with my placement of the source,
-400. -400. -320. mm, that I misunderstood somehow so it's outside the
camera somewhere. The actual patient doesn't fill the entire 128x128x103
image, so should I set the position according to patient or entire image?
Anyway, are there other errors in my source macro??
thanks for any help!
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