<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> <HTML> <HEAD> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> <META NAME="Generator" CONTENT="MS Exchange Server version 6.5.7651.59"> <TITLE>RE: [Gate-users] Energy deposited by Compton interaction</TITLE> </HEAD> <BODY>  Hi, Anayisse, Do you have a specific purpose needed to study from hits? To start from hits data file, you really need a clear idea what the hits are about and how they are recorded. I suggest you reading Geant4 manual about step function and GATE manual about hit carefully. See below for specific answer for your question. Yu Chen, Ph.D. University of Massachusetts Medical School Division of Nuclear Medicine 55 Lake Avenue North Worcester, MA 01655-0243 Phone:  (508) 856-6123 Fax:    (508) 856-4572 -----Original Message----- From: gate-users-bounces@lists.healthgrid.org on behalf of anayisse arnaud Sent: Fri 12/21/2007 11:43 AM To: gate-users@lists.healthgrid.org Subject: [Gate-users] Energy deposited by Compton interaction Dear Gate users, I hope you can help me explain these results : I have always the energy deposited by Compton interaction = 0 , it's impossible .... !! can you help me understand why ? A: Yes, it is possible. It indeed is designed in Geant4 to have one step (hit) for each Compton scattering process no matter whether the required step length is longer than input parameter of interaction range. In this step, a scattered electron is generated and the initial photon momentum is recalculated. Therefore no energy is deposited in this step. Energy deposits are by following scattered electron through ioning (eIoni) and multiple scattering (msc) processes, and by scattered photon through photoelectric (phot) process. Of course, the scattered photon can occur another compton process as indicated by your gateHits.dat below. Can you tell how those two photons from your primary source transport from your gateHits.dat? -Yu Here some lines from the gateHits.dat file after a very simple PET scanner simulation :        0       4   2   0     0    98     0     0     0     0   4.80830738641700296894139e-05  0.000e+00  5.900e+00  5.387e+00 -6.378e+01 -8.914e+00      22     2     0   1    0    0 compt NULL NULL        0       4   2   0     0    98     0     0     0     0   4.80830738648918237332190e-05  2.890e-03  1.164e-04  5.387e+00 -6.378e+01 -8.914e+00      11     3     2   1    0    0 eIoni NULL NULL        0       4   1   0     0   930     0     0     0     0   4.80830725456377712154210e-05  0.000e+00  5.505e+00 -5.354e+00  6.339e+01  8.859e+00      22     1     0   2    0    0 compt NULL NULL        0       4   1   0     0   930     0     0     0     0   4.80830725460870645956990e-05  1.033e-02  8.112e-04 -5.354e+00  6.339e+01  8.859e+00      11     4     1   2    0    0 eIoni NULL NULL        0      15   2   0     0   509     0     0     0     0   1.75863105737611002260534e-04  0.000e+00  5.199e+00  5.937e+01 -9.981e+00 -2.245e+00      22     2     0   1    0    0 compt NULL NULL        0      15   2   0     0   637     0     0     0     0   1.75863124194323804235993e-04  5.024e-02  1.904e+00  5.555e+01 -7.918e+00  1.178e+00      22     2     0   1    0    0 phot NULL NULL        0      15   2   0     0   637     0     0     0     0   1.75863124237332288379854e-04  1.345e-01  5.869e-02  5.554e+01 -7.914e+00  1.184e+00      11     4     2   1    0    0 eIoni NULL NULL        0      15   2   0     0   509     0     0     0     0   1.75863105817652010803842e-04  6.486e-02  3.775e-02  5.940e+01 -9.974e+00 -2.234e+00      11     3     2   1    0    0 msc NULL NULL        0      15   2   0     0   509     0     0     0     0   1.75863105916834852647870e-04  2.614e-01  1.659e-01  5.941e+01 -9.980e+00 -2.217e+00      11     3     2   1    0    0 eIoni NULL NULL        0      23   2   0     0   244     0     0     0     0   2.79542904503920954916579e-04  0.000e+00  1.361e+00  4.617e+01 -3.233e+01 -5.875e+00      22     2     0   1    0    0 compt NULL NULL        0      23   2   0     0   374     0     0     0     0   2.79542924092678708378190e-04  5.024e-02  1.776e-01  5.034e+01 -2.825e+01 -5.234e+00      22     2     0   1    0    0 phot NULL NULL        0      23   2   0     0   374     0     0     0     0   2.79542924143725331903587e-04  2.290e-01  1.359e-01  5.035e+01 -2.824e+01 -5.231e+00      11     4     2   1    0    0 eIoni NULL NULL Thank you very much Anayisse _________________________________________________________________ Express yourself instantly with MSN Messenger! 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