Hi, <div>2008/1/24, Sanae Rechka <<a href="mailto:Sanae.Rechka@usherbrooke.ca">Sanae.Rechka@usherbrooke.ca</a>>:<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> Dear Gate users, Is it possible to place the CylindricalPET inside a large lead box or cylinder to store the energy of photons outside the scanner (photons which escape from the scanner)?</blockquote><div> One possibility is to define the world material to lead, an other is to define a big lead box over your CylindricalPET, but there is no interest to do such a thing because in lead your gammas will be stop before traversing one mm ! so they won't escape from your box and you will not be able to see them after. I don't really see a solution to your investigation at the moment but if I have an idea, I will send you (but I think this is not possible without modifying the gate source code and even the geant4 source code !) Good luck ! Simon </div> <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Of course, I am aware of this :                           Gate only stores hits for those volumes attached to a sensitive detector. A volume must belong to a system before it can be attached to a sensitive detector.  And system should be one of the systems defined in page 48 of the Gate users Guide. I'm aware of that.  And it's why I'm asking.... Can any body answer my question please ? Thank you very much in beforehand Sanae _______________________________________________ Gate-users mailing list <a href="mailto:Gate-users@lists.healthgrid.org"> Gate-users@lists.healthgrid.org</a> <a href="http://lists.healthgrid.org/mailman/listinfo/gate-users">http://lists.healthgrid.org/mailman/listinfo/gate-users</a> </blockquote></div>