[Gate-users] Re : Problem wih CT-Scans using different energies

[Zhihuaigu]

Dear Andreas,
 
It seems your program run well. The Physics.mac is no problem.   how many number of primaries have you set? Are you sure you set the two process the same number? Besides, the CT scanner.mac only count the number of photons it received, so you will get the same results no mater what materials you have used.
 
Regards,
 
zhaowei
IHEP, CAS


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Message: 1
Date: Wed, 26 Oct 2011 12:05:37 +0200
From: "Andreas Duschl" <duschl at hicat.de>
To: <gate-users at lists.opengatecollaboration.org>
Subject: [Gate-users] Problem wih CT-Scans using different energies
Message-ID: <000001cc93c6$cf152960$6d3f7c20$@de>
Content-Type: text/plain;    charset="iso-8859-1"

Dear Gate-Users



I'm trying to make a CT-Scan using Gate v6.0 . Basically I have extended the
CT-Scanner Example (classic) in order to make two scans of the same phantom
with two different energies (80kV and 140kV).  Therefore I calculated the
filtered spectra with the open source matlab tool Spektr which I then
included into the script source.mac . I also have set the energy window of
the digitizer from 10kV to 140kV. The strange thing is that in the low
energy projection the value of the SNR is greater than in the corresponding
high energy projection. Normally it should be the other way round. What I
already tried to do is using different detector materials such as ceasium
iodide and glass as back compartment. But all with the same effect. Maybe
I'm using the wrong physical effects due to the energy switch:



Bremsstrahlung

LowEnergyRayleighScattering

PhotoElectric

ElectronIonistation

Compton



Since I'm not a pysicist this is hard for me  to decide.



I really need to rely on the results. But how can I if even the effect with
the SNR is not correct. Does anyone have an idea what I'm doing wrong or
does anyone have already created a working set of scripts which covers
CT-Scans using different energies which he/she is nice enough to share?



Any help is appreciated. Thanks in advance.



Andreas





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Andreas Duschl - Diplommathematiker (FH)



hiCAT GmbH

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