[Gate-users] [ no subject ]

[Chen, Yu]

Dear MJ and others,

I think what Irene et al reported is possible since
benchmarkPET (and many other simulations) used blurring module
(e.g., 26% resolution in benchmarkPET). This will simply smear 
any small difference in no blurring application like Irene
did.

I am also puzzled by Irene's discovery:
Single's energy goes above norminal input energy without blurring in GATE
version 3.1.2.

First, it is not likely a coincidence sorter problem (but that less coincidence
events problem probably is.).

I think the problem could be due to:

1) GATE single (pulse) algorithm change?
If an algorithm of single like all hits within a certain time window are collected and accounted
for one pulse is implemented, it is possible to simulate pileup effect, and then we can see unreal larger energy for
one single. 

2) any change in Geant4?
which corresponding Geant4 version?
Is it possible that Genat4 loses correct track and time information for one event and wrongfully assigns those steps after
a certain time to next event?

To exclude those possibilities, a very low activity simulation will be helpful.

Irene et al., can you do this: repeat your simualtion in v 3.1.2 at a very low activity?   

Looking forward to seeing your new results.

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 Park MinJae
Sent: Mon 12/17/2007 8:20 PM
To: 'Jasmine Schirmer'; gate-users at lists.healthgrid.org
Subject: RE: [Gate-users] [ no subject ]
 
Dear Irene,

Let me check what you are saying...

There is no problem with benchmarkPET...
[In both the old and new versions of GATE, the benchmark PET was
successfully completed and no difference in the energy spectra was
observed.]

In your simulation code, uphold value is 950 keV...
[However, the upper energy threshold of the benchmark is set to
650keV while our simulations are performed at higher upper energy
thresholds.]
[/gate/digitizer/Singles/upholder/setUphold 950. keV]

In fact, I can't get that the benchmark is same but your code is
different...

Can I take a look on your code and simulate your code with my gate?

MJ

-----Original Message-----
From: gate-users-bounces at lists.healthgrid.org
[mailto:gate-users-bounces at lists.healthgrid.org] On Behalf Of Jasmine
Schirmer
Sent: Monday, December 17, 2007 11:24 PM
To: gate-users at lists.healthgrid.org
Subject: [Gate-users] [ no subject ]

Dear GATE users and developers,

A few weeks ago, we sent an email to the users list concerning a problem we
are having with the newest version of GATE. The email was dated the 29th of
November and is titled 'differences in energy spectra from different GATE
releases'.

At the moment, we can no longer use reliably the newest version of GATE
until this issue is resolved. To recall your attention, we showed a
difference in the energy spectra produced by two identical simulations using
two versions of GATE (version 3.0.0 and the newest 3.1.2). The newest
version gives a different and unexpected result for the energy spectra as
you can see from the figures attached in the previous email. (The energy
spectra does not fall to zero!)

We kindly ask the developers and users to address this issue. In addition,
if anyone would like to perform a similiar test on their version of GATE, we
would be happy to provide the macro we used.

Thanks in advance,
Irene Torres and Jasmine Schirmer

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