[Gate-users] Fwd: Benchmark disagreements

[Chen, Yu]

Quite interesting and a little surprised to me.

I tend to agree with Sebastein that the difference is due to
physics processes not simply due to statistics. Then to further understand
what is the difference is essential for us - Gate users.

Here is a list I can think out for a check:

               recommended results             current version

1,versions (GATE 1, 2? <- Geant4 4, 5? )    GATE 3 <- Geant4 8
2,physics list    standard or lowenergy?   
  process         Compton only?             Compton, Rayleigh?
3,thresholds      e, gamma for different processes

Assuming all of above 2,3 are the same for two GATE versions, then go to dig out:

What has been changed in Geant4 physics process?

One can compare by 
turning on Compton, off Rayleigh
turning off Compton, on Rayleigh

in two different GATE (G4) versions
to see which process caused the difference.

Is the difference reasonable?

If yes, we may try to validate the new GATE results and trust it.

if not, dig deeper into Geant4. Does GATE use default cross section table in G4?
Can we try other options in G4?


So far, that's it.

Hope it helps.

 
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



-----Original Message-----
From: gate-users-bounces at lists.healthgrid.org on behalf of Antigoni Divoli
Sent: Tue 7/3/2007 9:36 AM
To: gate-users at lists.healthgrid.org
Subject: [Gate-users] Fwd: Benchmark disagreements
 
Dear all,
about a month ago I posted a message regarding some discrepancies found
in the results of the SPECTbenchmark when compared with the suggested
results in the gate web-page. Some people reported similar
discrepancies. We took this issue a bit further 'privately' with
Sebastien and the end point was that could be due to different version
of G4 used by 'us' and that used to obtain the recommended results. 

Attached you can find our conversation which might be of interest to
you. 
If you have any comments/suggestions will be highly appreciated. 

Regards

Antigoni

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.

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