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<TITLE>RE: [Gate-users] Fwd: Benchmark disagreements</TITLE>
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<P><FONT SIZE=2>Quite interesting and a little surprised to me.<BR>
<BR>
I tend to agree with Sebastein that the difference is due to<BR>
physics processes not simply due to statistics. Then to further understand<BR>
what is the difference is essential for us - Gate users.<BR>
<BR>
Here is a list I can think out for a check:<BR>
<BR>
recommended results current version<BR>
<BR>
1,versions (GATE 1, 2? <- Geant4 4, 5? ) GATE 3 <- Geant4 8<BR>
2,physics list standard or lowenergy? <BR>
process Compton only? Compton, Rayleigh?<BR>
3,thresholds e, gamma for different processes<BR>
<BR>
Assuming all of above 2,3 are the same for two GATE versions, then go to dig out:<BR>
<BR>
What has been changed in Geant4 physics process?<BR>
<BR>
One can compare by<BR>
turning on Compton, off Rayleigh<BR>
turning off Compton, on Rayleigh<BR>
<BR>
in two different GATE (G4) versions<BR>
to see which process caused the difference.<BR>
<BR>
Is the difference reasonable?<BR>
<BR>
If yes, we may try to validate the new GATE results and trust it.<BR>
<BR>
if not, dig deeper into Geant4. Does GATE use default cross section table in G4?<BR>
Can we try other options in G4?<BR>
<BR>
<BR>
So far, that's it.<BR>
<BR>
Hope it helps.<BR>
<BR>
<BR>
Yu Chen, Ph.D.<BR>
University of Massachusetts Medical School<BR>
Division of Nuclear Medicine<BR>
55 Lake Avenue North<BR>
Worcester, MA 01655-0243<BR>
Phone: (508) 856-6123<BR>
Fax: (508) 856-4572<BR>
<BR>
<BR>
<BR>
-----Original Message-----<BR>
From: gate-users-bounces@lists.healthgrid.org on behalf of Antigoni Divoli<BR>
Sent: Tue 7/3/2007 9:36 AM<BR>
To: gate-users@lists.healthgrid.org<BR>
Subject: [Gate-users] Fwd: Benchmark disagreements<BR>
<BR>
Dear all,<BR>
about a month ago I posted a message regarding some discrepancies found<BR>
in the results of the SPECTbenchmark when compared with the suggested<BR>
results in the gate web-page. Some people reported similar<BR>
discrepancies. We took this issue a bit further 'privately' with<BR>
Sebastien and the end point was that could be due to different version<BR>
of G4 used by 'us' and that used to obtain the recommended results.<BR>
<BR>
Attached you can find our conversation which might be of interest to<BR>
you.<BR>
If you have any comments/suggestions will be highly appreciated.<BR>
<BR>
Regards<BR>
<BR>
Antigoni<BR>
<BR>
The Institute of Cancer Research: Royal Cancer Hospital, a charitable Company Limited by Guarantee, Registered in England under Company No. 534147 with its Registered Office at 123 Old Brompton Road, London SW7 3RP.<BR>
<BR>
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</FONT>
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