<div dir="ltr"><div>Hi Stathis,</div><div> </div><div>You defined an actor of 1x1x20 cm, which is centered in a volume of 50x50x50 cm. Therefore you do not get the first 15 cm and the build-up.</div><div>If you do not mentioned the size of the actor, the actor will automatically get the size of the volume.</div> <div>Just try:</div><div>#/gate/actor/doseDistribution/setSize 1 1 20 cm<br>/gate/actor/doseDistribution/setResolution 1 1 5000</div><div> instead of </div><div>/gate/actor/doseDistribution/setSize 1 1 20 cm<br> /gate/actor/doseDistribution/setResolution 1 1 2000</div><div> </div><div>If you absolutely want to use a size of 20 cm 1x1x20 cm, you should translate the actor position:</div><div>/gate/actor/doseDistribution/setPosition 0 0 -15 cm<br> /gate/actor/doseDistribution/setSize 1 1 20 cm<br>/gate/actor/doseDistribution/setResolution 1 1 2000</div><div> </div><div>Looking forward for the tutorial,</div><div> </div><div>Cheers,</div><div>LG </div> </div><div class="gmail_extra"><br clear="all"><div>Loīc<br></div> <br><br><div class="gmail_quote">2014-02-03 Stathis Kamperis <span dir="ltr"><<a href="mailto:ekamperi@gmail.com" target="_blank">ekamperi@gmail.com</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> Dear Gate users,<br> <br> for once more I will appeal to your expertise. I'd like to simulate a<br> point source of photons 20 MeV that diverges in space so that when it<br> hits my water tank it forms a 10x10 cm field. Subsequently, I'd like<br> to measure the dose depth along the central axis.<br> <br> I define the water phantom as:<br> <br> /gate/world/daughters/name waterTank<br> /gate/world/daughters/insert box<br> /gate/waterTank/placement/setTranslation 0 0 25 cm<br> /gate/waterTank/geometry/setXLength 50 cm<br> /gate/waterTank/geometry/setYLength 50 cm<br> /gate/waterTank/geometry/setZLength 50 cm<br> /gate/waterTank/setMaterial Water<br> <br> The above commands place the water phantom centered at (0,0,25). I<br> then put a source at (0,0,-100cm), i.e. a source coming from the<br> negative z-axis towards the positive z-axis:<br> <br> /gate/source/addSource mybeam gps<br> /gate/source/mybeam/gps/ene 20 MeV<br> /gate/source/mybeam/gps/particle gamma<br> /gate/source/mybeam/gps/ene/type mono<br> <br> /gate/source/mybeam/gps/position 0 0 -100 cm<br> /gate/source/mybeam/gps/pos/type Point<br> /gate/source/mybeam/gps/ang/type iso<br> <br> /gate/source/mybeam/gps/ang/mintheta 177.1376 deg<br> /gate/source/mybeam/gps/ang/maxtheta 180 deg<br> /gate/source/mybeam/gps/ang/minphi 0 deg<br> /gate/source/mybeam/gps/ang/maxphi 180 deg<br> <br> According to the gps documentation theta = 180 deg corresponds to a<br> beam travelling towards positive z-axis. Therefore, in order to form a<br> divergent beam that enters the water phantom as a 10x10cm field, I<br> need to restrict theta precisly atan(5/100) * 180 / pi = 2.8624 deg.<br> That is where 177.1376 comes from.<br> <br> I've looked at my geometry (X-Y, X-Z, Y-Z planes) and it looks ok.<br> <br> Finally, I put my dose actor at (0,0,0) which is along the central<br> axis of the phantom since z=0 is the entry point of my beam and the<br> whole phantom is centered at (0,0,25).<br> <br> /gate/actor/addActor DoseActor doseDistribution<br> /gate/actor/doseDistribution/attachTo waterTank<br> /gate/actor/doseDistribution/stepHitType random<br> /gate/actor/doseDistribution/setPosition 0 0 0 cm<br> /gate/actor/doseDistribution/setSize 1 1 20 cm<br> /gate/actor/doseDistribution/setResolution 1 1 2000<br> <br> (for brevity I skip the commands that are not related to geometry)<br> <br> The dose actor will output 2000 values that correspond to the 20cm<br> worth of water phantom (I suppose). The first value corresponding to<br> depth z=0, the 2nd value for z=0.01cm and so on. Is that correct or do<br> I have to specify some sort of direction to the actor ?<br> <br> Also the one million dollar question. The dose profile that I get does<br> not make sense to me at all. I'm not seeing any build-up region. Here<br> is the plot:<br> <br> <a href="http://dl.dropbox.com/u/25202446/opengate2.png" target="_blank">http://dl.dropbox.com/u/25202446/opengate2.png</a><br> <br> Does that make sense to you ?<br> <br> Thank you for your patience and I promise I'll write up a nice<br> tutorial for novices like me when I master Gate!<br> <br> Best regards,<br> Stathis<br> _______________________________________________<br> Gate-users mailing list<br> <a href="mailto:Gate-users@lists.opengatecollaboration.org">Gate-users@lists.opengatecollaboration.org</a><br> <a href="http://lists.opengatecollaboration.org/mailman/listinfo/gate-users" target="_blank">http://lists.opengatecollaboration.org/mailman/listinfo/gate-users</a><br> </blockquote></div><br></div>