[gate-users] about random coincidences

[yuxuan.zhang at di.mdacc.tmc.edu]

hi all,

In my simulation I noticed a strange result that I can not figure it out.
My setup is that: using cylindricalPET system with 30 rsetors, one point
source at the center. The radiation activity is very high, thus there are
lots of random coincidences (accidental coincidences) in the totoal
coincidences. Now I do the statistics on these random coincidences 
according
to the sector index, then I found that the coincidences between 2 opposite 
rsectors 
(e.g. No.0 and 15, or No.5 and 20) are much more than the coincidences 
between other
2 sectors ( No. 0 and 14, or No. 0 and 16 ...) Usually the difference can 
be 50% or 100% depend on the thickness of the detector. Is anyone else 
noticed that?
Can you have a try in your computer to find out whether this is a bug of 
GATE or there
is somthing wrong with my simulation? Thank you very much.


Best regards,

Yuxuan Zhang


Dr. Yuxuan ZHANG 
Dept. Experimental Diagnostic Imaging
Univ. Texas, MD Anderson Cancer Center
1515 Holcombe Blvd, Unit 217
Houston, TX 77030-4095

Tel: +1-713-745-1671 
Fax: +1-713-745-1672
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