Hi Sanae, <div>2008/1/25, 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;"> Hi Simon, Done :  I confirmed by simulation what was said in the Gate users Guide : we can only record Hits in volumes belonging to the scanner. I tried the two solutions you proposed, but they don't work. And as you said there is no solution without modifying the gate source code.</blockquote><div> OK, too bad ... Nevertheless, perhaps I have a solution, but it is a do-it-yourself method ! If you build a very very large cylindricalPET (I mean your original scanner but where rsectors have a huge length on z axis, ideally infinity !) you could stop almost every gammas which should go outside your original scanner. Then everything will be done in the postprocessing. Assuming the z length of your rsector from your original scanner is zOrig, and the output format is ROOT. Then for each Singles, you take the globalPosZ variable (which represents the z cartesian coordinate where your gammas was detected) and you check whether this variable is lower than -zOrig/2 or higher than +zOrig/2. If it's the case then it means that your gamma should go outside your original scanner and so you can get the energy and everything that you are looking for. The only problem is how big your z length should be to get the lower error and to loose the lower quantity of  the emitted gammas. I realise now that maybe you want to get photons that go inside your crystals and then go outside without doing a photoelectric interaction. In this case, you have to build deeper rsectors and crystals than the original ones and proceed with the same idea. You take the globalPosX and globalPosY variables, then calculate the angle of the position from the x axis (or y axis), then calculate with that angle the maximum xOrig and yOrig values from where your photon will be outside the original rsector and see by doing an other calculation if your x and y values are higher (or lower, it depends on the angle value) than the xOrig and yOrig values, which means that the photon is out of your original scanner !!! Very simple ;-) It's really much more complicated than the first method but it depends on what you want to get. Am I clear in this message, do I really understand what you want to do ? In any case, I hope this will work, Cheers, Simon </div> <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> Thanks and Have a nice day Sanae ----- Message transféré de Sanae Rechka <<a href="mailto:Sanae.Rechka@USherbrooke.ca">Sanae.Rechka@USherbrooke.ca</a>> -----    Date : Thu, 24 Jan 2008 18:54:00 -0500      De : Sanae Rechka <<a href="mailto:Sanae.Rechka@USherbrooke.ca">Sanae.Rechka@USherbrooke.ca</a>> Adresse de retour :Sanae Rechka <<a href="mailto:Sanae.Rechka@USherbrooke.ca">Sanae.Rechka@USherbrooke.ca</a>>   Sujet : Re: [Gate-users] CylindricalPET inside a large lead box or cylinder ?       À : Simon Stute <<a href="mailto:gate.stute@gmail.com">gate.stute@gmail.com</a>> Hi Simon, Thank you very much for your answer, - But if we define the world material to lead, can we record Hits in the world material ?  even If Gate only stores hits for those volumes attached to a sensitive detector and belonging to a system.  And system should be one of the systems defined in page 48 of the Gate users Guide (which mean CylindricalPET, SPECT, ECAT, etc...) ????? - for the second solution : to define a big lead box over your CylindricalPET, in lead your gammas will be stopped before traversing one mm ! so they won't escape from your box and you will not be able to see them after. This is Ok, it's what I need. But can we record Hits in the Box over the scanner ? because according to the GATE users Guide we can only record Hits in volumes belonging to the scanner ? isn't it ? Sanae Selon Simon Stute <<a href="mailto:gate.stute@gmail.com">gate.stute@gmail.com</a>>: > Hi, > > 2008/1/24, Sanae Rechka <<a href="mailto:Sanae.Rechka@usherbrooke.ca">Sanae.Rechka@usherbrooke.ca</a>>: > > > > > > 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)? > > > 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 > > 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> > > > ----- Fin du message transféré ----- </blockquote></div>