<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <meta name="Generator" content="Microsoft Word 14 (filtered medium)"> <style></style> </head> <body lang="EN-US" link="blue" vlink="purple"> <div class="WordSection1"> Hi Stathis,<o:p></o:p> <o:p> </o:p> What you should observed is the following:<o:p></o:p> <![if !supportLists]>- <![endif]>At the center: a higher energy and a lower fluence due to the filter thickness<o:p></o:p> <![if !supportLists]>- <![endif]>With increased radial distance: a reduced mean energy and increased fluence<o:p></o:p> <![if !supportLists]>- <![endif]>At the filter border: you suddenly have no filter material, so the fluence increases and the mean energy decrease.<o:p></o:p> Actually, what happens at the border of the filter is not important, in the sense that this part of the beam is not use clinically.<o:p></o:p> <o:p> </o:p> Sincerely,<o:p></o:p> <o:p> </o:p> Loïc<o:p></o:p> <o:p> </o:p> <o:p> </o:p> <o:p> </o:p> From: gate-users-bounces@lists.opengatecollaboration.org [mailto:gate-users-bounces@lists.opengatecollaboration.org] On Behalf Of Stathis Kamperis Sent: Freitag, 9. Mai 2014 19:15 To: gate-users Subject: Re: [Gate-users] Mean energy vs. Radial distance in Elekta Precise 6MV phase-space data<o:p></o:p> <o:p> </o:p> Στις 9 Μαϊ 2014 10:28 π.μ., ο χρήστης "Stathis Kamperis" <<a href="mailto:ekamperi@gmail.com">ekamperi@gmail.com</a>> έγραψε: > > Hello everyone, > > I'm using the Elekta Precise 6MV phase space data from the site of > IAEA. I was plotting the mean photons' energy vs. radial distance and > there's a peak around ~6-7.5cm that I cannot explain: > > <a href="http://dl.dropboxusercontent.com/u/25202446/peak.png">http://dl.dropboxusercontent.com/u/25202446/peak.png</a> > > Also, the graph from here > <a href="http://www.creatis.insa-lyon.fr/~dsarrut/articles/Grevillot2011.pdf">http://www.creatis.insa-lyon.fr/~dsarrut/articles/Grevillot2011.pdf</a> > lacks such a peak (not sure if it is the same exact linac model). > > The closest clue I could get is from Grevillot et al: > > "... step in the particle radial ﬂuence is observed between 65 and 70 > mm in (b), corresponding to interactions of the photons with the ﬂat > bottom edge of the ﬂattening ﬁlter." > > Do you have any suggestion on how to interpret my results ? Perhaps > the simulation of the IAEA phase-space data used a smaller flattening > filter ? And too many photons pass through its edge ?<o:p></o:p> Actually that doesnt make sense. We are plotting mean energy, not fluence. <o:p> </o:p> (I think that > the plot code is correct, since it uses the fields package of R.) > > Thank you for your consideration, > > Best regards, > Stathis<o:p></o:p> </div> <div class="WordSection1"> <o:p></o:p>Disclaimer: Please notice our E-Mail Disclaimer <a href="http://www.medaustron.at/email-disclaimer/">http://www.medaustron.at/email-disclaimer/</a><o:p></o:p><o:p> </o:p> </div> </body> </html>