[gate-users] Phantom problem

[Mikhail Shilov]

Thanks everyone who responded to my inquiry about energy spectrum of the
detected gamma photons.
After careful examination of my gateHits.dat output file I finally
figured out the reason for my confusion and why I was getting so much
noise in the output sinograms. 

In my test simulation I used a single ring camera which consists of
6X112 BGO crystals grouped in 112 blocks. I use a e+ point source in the
center surrounded by a 10 mm thick water phantom. Since the mean free
path of a positron in water is about 1mm, I assumed that the all
annihilations should happened in the phantom near the source. 

Never the less, when I analyzed my gateHits.dat output of the run I
found out that almost all the annihilations happened in the BGO crystals
( I did attached the phantom to SD with /gate/myphantom/attachPhantomSD
). It looked like the phantom didn't even exist in the simulation.

Here is macro for my phantom. I don't see anything wrong with it:

/gate/ecat/daughters/name myphantom
/gate/ecat/daughters/insert cylinder
/gate/myphantom/geometry/setRmax 10.0 mm
/gate/myphantom/geometry/setHeight 20.0 mm
/gate/myphantom/placement/setTranslation 0.0 0.0 0.0 cm
/gate/myphantom/setMaterial Water
/gate/myphantom/vis/forceSolid
/gate/myphantom/vis/forceWireframe
/gate/myphantom/vis/setColor green

/gate/myphantom/attachPhantomSD

a point source is in the origin ( 0. 0. 0. )

If anyone have any suggestions for my problem it would greatly
appreciated.

Mikhail A. Shilov
The Johns Hopkins University
Department of Radiology
Tel:  443-287-7315
Fax:  410-614-1977
mailto: mshilov1 at jhmi.edu