[gate-users] GPS source angular distribution (Visualization)/Uniform Cylinder image

Mutanga Theodore muathe02 at student.umu.se
Wed Sep 21 15:47:32 CEST 2005

Greetings ,

I was doing some simulations involving 'irregular' cylinders ie my phantom
contains a cylinder modified with the

.../geometry/setPhiStart 270. deg
.../geometry/setDeltaPhi  90. deg


The gemotries in question are halfcylinders. I would like to place sources
in those irregular volumes and I can't find the GPS commands that are
equivalent to those two above. Has anyone any ideas about this? I have
been thinking about using the /ang/minThetha and ang/minPhi to describe
the distribution of the sources but Im not sure if this is ok since we
can't visualize sources.

I have looked at the GPS commands and it seems sources can be visualized
in geant4 and not GATE why is that ?

This one is about corrections for scatter:

Below is an image of a uniform cylindrical source , data reconstructed
with STIR OSEM ( no arc correction was done but I forced the OSMAPOSL to
think that the data was arc-corrected for)STIR only has arc-correction for

The line profile accross the central slice shows the expected 'dip' at the
the image is not satisfactorily uniform and I would like to find out some
fo the things I can modify about my scanner design, reconstruction and
data correction techniques to get the image as uniform as possible.

I collected some 10^6 coincidences and I am currently running another
simulation at an off-centre position just in case the scanner was behaving
funny at the centre.

Is there some means of doing scatter/random correction on GATE data before
writing to the root file ? If not what are some possible methods of
removing those unwanted coincidences from say the root file?

I hope to hear from someone with suggestions.



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