[Gate-users] inhomogeneous activity distribution in several outputfiles

[Hans-Martin Schwab]

   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
   <[1]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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