[Gate-users] Artefact in Interfile output

[Albert Hirtl]

Hi Uwe,

Thanks again for the answer. Our artefacts vanished by using 
MersenneTwister, just like you proposed.

Thanks!

Cheers,
Albert

On 03/11/11 11:03, Uwe Pietrzyk wrote:
> Hi Albert,
>
> we had a similar problem, though not for simulating a SPECT system.
> We finally found that using the "Ranlux64" consistently produced
> artefacts, which become visible on long runs as yours. We have now
> switched to the "MersenneTwister". Maybe you could give it a try.
>
> Kind regards and best wishes
>
> Uwe Pietrzyk
> -----
> On 03.11.2011, at 10:44, Albert Hirtl wrote:
>
>> Dear Gate-users,
>>
>> We are somewhat stuck :-) . We are trying to simulate a two-headed
>> SPECT-system with a very simple (cylindrical) water phantom inside. The
>> source is a gamma emitter with 140 keV. In principle things are fine,
>> however, there are some artefacts (?) in the interfile output. If you
>> please have a look at the attached image (need to zoom a little), you
>> see  some lines in the slices 9 and 73 (these are opposing SPECT-heads),
>> which I do not understand. They also appear at other slices (29-93,
>> 47-111, 59-123). Since these lines always occur in pairs, their origin
>> must probably be in the source somewhere. Has anybody ever seen such a
>> behaviour?
>>
>> I also attached the relevant mac-files, maybe it is some trivial mistake
>> in one of the mac files. Any help would very much be appreciated!
>>
>> Cheers,
>> Albert
>>
>> -- 
>> Medizinische Universität Wien - Allgemeines Krankenhaus Wien
>> Universitätsklinik für Nuklearmedizin
>> Währinger Gürtel 18-20
>> 1090 Wien
>> Austria
>>
>> Tel.: +43 (0) 1 / 40400 5545
>>
>> Web:
>> http://www.meduniwien.ac.at/user/albert.hirtl
>> http://www.meduniwien.ac.at/moccamed/
>> http://www.meduniwien.ac.at/nuklear/forschunglehre/physik/index.html
>>
>> <100MBq_2headsSPECT.jpg><MainSPECT.mac><Activity.mac><CollimatorVPC45K.mac><Digitizer.mac><OutputTime.mac><PhantomSource.mac><Physics.mac><SystemGeometry.mac><albert_hirtl.vcf>_______________________________________________
>> Gate-users mailing list
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>> http://lists.opengatecollaboration.org/mailman/listinfo/gate-users
>
> /----------------------------------------------------------------------
> Prof. Dr. Uwe Pietrzyk
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-- 
Medizinische Universität Wien - Allgemeines Krankenhaus Wien
Universitätsklinik für Nuklearmedizin
Währinger Gürtel 18-20
1090 Wien
Austria

Tel.: +43 (0) 1 / 40400 5545

Web:
Personal: http://www.meduniwien.ac.at/user/albert.hirtl
MoccaMed: http://www.meduniwien.ac.at/moccamed