[Gate-users] inhomogeneous activity distribution in several outputfiles

[Simon Stute]

Hey,

OK, at least it is good that your problem is solved !
And thanks for pointing out the Ranlux problem.
Which version of GATE are you using, and linking with which version of clhep
?
But anyway, the MersenneTwister is probably the best random number generator
(in efficiency and in accuracy), even if it is not obvious to notice that in
daily's work ! So if your simulations run safe using the JamesRandom one,
just keep it :-)

Cheers,
Simon

On Mon, Jan 3, 2011 at 4:56 PM, Hans-Martin Schwab <
hans-martin.schwab at web.de> wrote:

> Hello,
> thanks a lot, I tested that but it didn´t have any effect on my results.
> Moreover I did not use a back-to-back source.. Well I made some attempts
> using the JamesRandom-generator and now everything seems to work properly. I
> don´t know why, but this appears to have been a problem with the Ranlux64..
> Best regards,
> Hans
>
>  ------------------------------
> *Von:* "Simon Stute" <gate.stute at gmail.com>
> *Gesendet:* 28.12.2010 19:40:50
> *An:* "Hans-Martin Schwab" <hans-martin.schwab at web.de>
> *Betreff:* Re: [Gate-users] inhomogeneous activity distribution in several
> outputfiles
>
>
> Hey,
>
> Didi you use backtoback sources ?
> Which version of Gate do you use ?
> It could be a problem with a non-initialized value in the code, concerning
> the non-collinearity flag when using backtoback sources.
> I encountered such a bug before, and it seemed to be fixed once I forced
> acolinearity to be true or false (whatever you want, it is just that this
> flag has no default value in the source code, and thus if the flag "decided"
> to be true, a non-initialized acolinearity angle is also used ... thus
> giving funny thing ...).
>
> Hope this helps,
> Simon
>
> On Thu, Dec 23, 2010 at 3:24 PM, Hans-Martin Schwab <
> hans-martin.schwab at web.de> wrote:
>
>>   Hello everybody,
>>   for my recent simulations I wrote a script in Root that creates a
>>   threedimensional .raw-file storing the activity distribution as derived
>>   from the sourcePos information in the coincidence dataset. Observing
>>   that raw-file one can see irregularities in the source-distribution
>>   that can even be recognized in the reconstructed image of the
>>   simulation data. There are several artifacts, that become visible. For
>>   some phantoms a area of a higher number of counts is noticable in the
>>   x-z-plane, although a homogeneous distribution is expected. Other
>>   images show hot planes orientated diagonally across each subvolume. Of
>>   course the data stored in the sourcePos dataset does not yet contain
>>   corrections of sensitivity and scatter, but the shape of these areas
>>   with more counts can not be explained by those issues. What
>>   is surprising, is that when I run the same script for several times
>>   (where only the output name distiguishes) these irregularaties
>>   sometimes occur and sometimes not. Does anybody have an idea about
>>   that? We suppose the random generator to play a role in this (in the
>>   macros the Ranlux64 is used), but still we canA't really find a
>>   consistent idea of what might cause those artifacts.
>>   Best regards,
>>   Hans
>>
>>
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>>
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