[gate-users] Crystal ID and position of Singles in PET

[Angela M K Foudray]

Hi Yu,

Have you looked at the hits file for the same simulation?  My guess is
that the Compton interactions in the detector and their corresponding
energy blur are making the global position and the crystal ID possibly
not line up.  I don't know how the crystalID is calculated for a single
(since the single can be made of multiple hits with their own crystal
ID) - for instance, the x,y,z position of a single could potentially not
end up in any crystal at all in a system with gaps between crystals...

So maybe looking in the hits file will help track things down?

Ange

On Tue, 2006-03-14 at 16:36 -0500, Chen, Yu wrote:
> Hi, Gaters,
> 
> When I try to convert the global position (globalPosX, Y, Z) of Singles in PET
> to corresponding rsectorID and crystalID, I found there is discrepancy between
> converted crystalID and recorded crystalID, namely, ~10% with -1 (converted - output)
> distributed within lower half of the same rsector while ~10% with +1 in upper half.
> Here lower, upper are defined along anti-clock-wise (increased azimuthal direction in
> X-Y plane).
> 
> Has anybody investigated this before?
> 
> I am using cylindricalPET geometry and setDepth 1, which means Singles are readout from 
> rsector with all pulses in all crystals in that rsector. A singles will take that pulse's
> crestalID and position with max energy. So expected discrepancy should be very small
> due only to float calculation. Am I right? If yes, what's wrong here?
> 
> Thanks,
>   
> 
> Yu Chen, Ph.D.
> University of Massachusetts Medical School
> Division of Nuclear Medicine
> 55 Lake Avenue North
> Worcester, MA 01655-0243
> Phone:  (508) 856-6123
> Fax:    (508) 856-4572
> 
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-- 
Angela M K Foudray <afoudray at stanford.edu>