[Gate-users] [ no subject ]

[Chen, Yu]

Dear All,

I would provide my thoughts for this problem. 
Before that, I would clarify those findings by Irene and Jasmine.

1) same results on benchmarkPET for two GATE versions 3.0.0 and 3.1.2.

2) different results on ECAT etc.

We know that benchmarkPET has 26% energy bluring. 
We want to know whether all diffrent results Irene et al got were from no blurring. 
Irene and Jasmine, can you confirm this?

If so, I suspect that problem is due to improper work in new GATE when energy bluring module
is turned off if it is not a simple mismatch problem among GATE, Genat4, clhep versions.

To confirm, I suggest:

1) MJ, repeat in your new GATE what Jasminge did. i.e, set bluring 0 and plot single energy in *LOG* scale.
We should expect some distribution above 511 keV.

2) Jasmine, set your bluring say 0.01 (1%) to see if those singles above ~550 keV disappear. (Again, LOG scale single energy plot!)
will those coincidence count be normal?

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 Jasmine Schirmer
Sent: Tue 12/18/2007 7:49 AM
To: MJ at ToTi.us; gate-users at lists.healthgrid.org
Subject: Re: RE: [Gate-users] [ no subject ]
 
Dear Min-Jae and GATE developers,

Thank-you for looking into this problem. We are attaching an example of a simple GATE simulation (single_layer.mac and the supplementary macros: no_visu.mac, physics.mac, single_layer_allmod.mac, CylFOV_Ph.mac and G_CapillariesS_5m_2D.mac ). You can run this simulation by using the command ./control/execute/single_layer.mac. We have run this on two versions of GATE. You will see that if you run this simulation using the newest version 3.1.2, you will obtain for the singles and coincidences, energy spectra which do not fall to zero. The output is as follows for a 400keV low energy threshold:

There are: 868838 Singles
=> 35514 coincidences
=> 4395 intercrystal coincidences
=> 9888 randoms
=> 2264 intercrystal randoms

where intercrystal coincidences are true coincidences detected in the same rsector. On the other hand, running the SAME macro under an older version of GATE (we used 3.0.0), the energy spectra falls to zero as expected with the following output:

There are: 867717 Singles
=> 50812 coincidences
=> 0 intercrystal coincidences
=> 9438 randoms
=> 2199 intercrystal randoms

This bug in the newest version of GATE means that we cannot use the output data reliably and our reconstructed images are incorrect.

We have noticed that this problem has also been detected by Georgi Gerganov. As well, we have seen the same problem using an ECAT simulation (0_ScriptSystem.mac and 0_ScriptSystem.mac). The resulting plots from this simulation have been posted with the November 29th email to the GATE mailing list.

Please let us know if you have any further questions.

Thanks in advance,
Irene and Jasmine 

Original Message:

Dear Irene,
<br />
<br />Let me check what you are saying...
<br />
<br />There is no problem with benchmarkPET...
<br />[In both the old and new versions of GATE, the benchmark PET was
<br />successfully completed and no difference in the energy spectra was
<br />observed.]
<br />
<br />In your simulation code, uphold value is 950 keV...
<br />[However, the upper energy threshold of the benchmark is set to
<br />650keV while our simulations are performed at higher upper energy
<br />thresholds.]
<br />[/gate/digitizer/Singles/upholder/setUphold 950. keV]
<br />
<br />In fact, I can't get that the benchmark is same but your code is
<br />different...
<br />
<br />Can I take a look on your code and simulate your code with my gate?
<br />
<br />MJ
<br />
<br />-----Original Message-----
<br />From: gate-users-bounces at lists.healthgrid.org
<br />[mailto:gate-users-bounces at lists.healthgrid.org] On Behalf Of Jasmine
<br />Schirmer
<br />Sent: Monday, December 17, 2007 11:24 PM
<br />To: gate-users at lists.healthgrid.org
<br />Subject: [Gate-users] [ no subject ]
<br />
<br />Dear GATE users and developers,
<br />
<br />A few weeks ago, we sent an email to the users list concerning a problem we
<br />are having with the newest version of GATE. The email was dated the 29th of
<br />November and is titled 'differences in energy spectra from different GATE
<br />releases'.
<br />
<br />At the moment, we can no longer use reliably the newest version of GATE
<br />until this issue is resolved. To recall your attention, we showed a
<br />difference in the energy spectra produced by two identical simulations using
<br />two versions of GATE (version 3.0.0 and the newest 3.1.2). The newest
<br />version gives a different and unexpected result for the energy spectra as
<br />you can see from the figures attached in the previous email. (The energy
<br />spectra does not fall to zero!)
<br />
<br />We kindly ask the developers and users to address this issue. In addition,
<br />if anyone would like to perform a similiar test on their version of GATE, we
<br />would be happy to provide the macro we used.
<br />
<br />Thanks in advance,
<br />Irene Torres and Jasmine Schirmer
<br />
<br />_______________________________________________
<br />Gate-users mailing list
<br />Gate-users at lists.healthgrid.org
<br />http://lists.healthgrid.org/mailman/listinfo/gate-users
<br />

-- 

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