[gate-users] Discovery ST images

[Mutanga Theodore]

Greetings Sadek, Kris

I finally got some decent images from my GATE simulations of the DST. I
modified all the necessary parameters in Sadek's code and then used
OSMAPOSL with Ray Tracing Matrix (default parameters).
For data compression in 3D mode I used a mashing factor of 2 and a span of
0 ( suggested by STIR) The maximum ring difference was 23. I have attached
two images of the sinograms and the reconstructed images of the three
point sources as mentioned in NEMA2001. ( I haven't yet done the setup at
1/4FOV)(NEMA 2001 says to use FBP for spatial resolution but I can't use
STIR for FBP on DST data yet, as Kris said in his last mail)

The first set of my questions goes to other GATERS:

I am using this images to measure the resolution (NEMA 2001) and I know it
depends on ring diameter crystal , reconstruction algorithm amongst
others.
19 I have done a rough estimate of the FWHM in three orthogonal directions
using AMide and the FWHM Im getting is off the expected by 1-1.5 mm in all
three directions. Given that I designed the system using the
cylindricalPET system, what factors could I adjust to get the desired
result ? the crystal size is standard nothing to be done there.

For the ring diamter, STIR says it is 90.3cm for DST but I have 88.6 cm
and I used STIR for reconstrction, how big an error does this give me ?

Also the bin size read off from GATE ( 1/2
crystal-center-to-crystal-center ) is 3.27 mm while STIR uses 3.1695 mm.

The next part is for arc correction of the data.  How is this done , in
STIR that is ? I just modified to header file to say the data was arc
corrected but I know that GATE han't done that.

At least it was nice to modify Sadeks code for the DST, another minor
detail is the orientation of the x and y axis in ECAT Hr+ and DST . they
seem to be mirror images, I noticed this from inspecting the location of
the pointsources, any harm with that ?


I appreciate all your comments .


theodore








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