<html dir="ltr"><head> <meta http-equiv="Content-Type" content="text/html; charset=Windows-1252"> <style id="owaTempEditStyle"></style><style title="owaParaStyle"></style> </head> <body ocsi="x"> <div style="FONT-SIZE: x-small; COLOR: #000000; DIRECTION: ltr; FONT-FAMILY: Tahoma"> <a></a>Dear Gate-users<a></a> <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> <o:p></o:p> I am<a></a> using<a></a> Gate<a></a> to simulate<a></a> a CT acquisition chain<a></a> (GE tomex<a></a> L 450) used<a></a> for CT analysis<a></a> of aeronautical<a></a> parts.<o:p></o:p> The main issue I am<a></a> facing<a></a> is<a></a> computing<a></a> time, especially<a></a> if I want<a></a> to simulate<a></a> a full scan (2400 projections at<a></a> I= 2ma<a></a>, V = 350 kV. (One of) my<a></a> “test” setup is<a></a> an epoxy<a></a> cylinder<a></a> located<a></a> 50 cm from<a></a> the tube, with<a></a> the detector at<a></a> 1m<a></a> from<a></a> the tube, if I propagate<a></a> 500 000 (as a benchmark) photons the “user”computing<a></a> times are the following<a></a>:<o:p></o:p> 31.15 seconds without<a></a> optimization<a></a> (Only<a></a> setting the simulation as /fast<a></a>/ to avoid<a></a> losing<a></a> one hour<a></a> computing<a></a> a 2048x2048<a></a> pixels grid<a></a>)<o:p></o:p> 30.8 seconds if I play<a></a> with<a></a> MaxStepSize<a></a> (Actually<a></a>, if I do /gate<a></a>/physics<a></a>/SetMaxStepSizeInRegion<a></a> world 15.0 mm, is<a></a> the step<a></a> size reset to a normal value when<a></a> entering<a></a> another<a></a> material<a></a> ? )<o:p></o:p> 31.71 seconds if I set VRT<a></a> to 10 (as in the benchmarkCT<a></a>/vrt<a></a> example<a></a>)<o:p></o:p> This important CPU<a></a> time makes<a></a> me fear<a></a> that<a></a> I cannot<a></a> compute<a></a> nor<a></a> a realistic<a></a> amount<a></a> of photon, neither<a></a> a realistic<a></a> number<a></a> of projections, so<a></a> I need<a></a> to find<a></a> some<a></a> way<a></a> to reduce<a></a> computing<a></a> time while<a></a> keeping<a></a> useful<a></a> informations) Is-there<a></a> any<a></a> option similar<a></a> to thinning<a></a>/weighting<a></a> (but for primaries<a></a> since<a></a> I am<a></a> not interested<a></a> in secondary<a></a> electrons<a></a>) to increase<a></a> luminosity<a></a> without<a></a> increasing<a></a> computing<a></a>-time? Is there<a></a> any<a></a> other<a></a> way<a></a> to reduce<a></a> the simulation time? Does<a></a> the vrt<a></a> increase<a></a> the weight<a></a> of a photon hitting<a></a> the detector and thus<a></a> increase<a></a> virtually<a></a> the number<a></a> of photons? (I haven't<a></a> tried<a></a> yet<a></a> to generate<a></a> images with<a></a> the vrt<a></a> enabled<a></a>) <a></a>Another question, even<a></a> though<a></a> the default source is<a></a> conical<a></a>, I'd<a></a> like<a></a> to take<a></a> into<a></a> account<a></a> the Gaussian-shape<a></a> of the X-ray spot, is<a></a> there<a></a> advanced<a></a> setting of the source in the macros? If not-is<a></a> there<a></a> any<a></a> Cpp<a></a> example<a></a>?<o:p></o:p> A last question, how do I find<a></a> the history<a></a> of a hit, when<a></a> parsing<a></a> the ntuple<a></a>, can<a></a> I find<a></a> information about the hit's<a></a> history<a></a>, whether<a></a> the photon has been scattered<a></a>, and through<a></a> which<a></a> material<a></a> has it<a></a> been propagated<a></a> ? i.e. how do I make<a></a> the difference<a></a> between<a></a> <o:p></o:p> 0 0.0116 0.013 -150 0.156 0 0 0 world_phys<a></a> initStep<a></a><o:p></o:p> 1 0.433 -4.18 -12 0.156 0 138 138 epoxyCylinder_phys<a></a> Transportation<o:p></o:p> 2 0.458 -4.42 -3.97 0.156 0 8.02 146 CCylinder_phys<a></a> Transportation<o:p></o:p> 3 0.482 -4.66 3.97 0.156 0 7.95 154 epoxyCylinder_phys<a></a> Transportation<o:p></o:p> 4 0.506 -4.9 11.8 0.156 0.000291 7.81 162 epoxyCylinder_phys<a></a> Compton<o:p></o:p> 5 0.539 -4.87 12 0.156 0 0.216 162 world_phys<a></a> Transportation<o:p></o:p> 6 22 12.5 150 0.156 0 141 303 pixel_phys<a></a> Transportation<o:p></o:p> And <o:p></o:p> 0 -0.0249 -0.017 -150 0.114 0 0 0 world_phys<a></a> initStep<a></a><o:p></o:p> 1 -4.21 0.707 -11.2 0.114 0 139 139 epoxyCylinder_phys<a></a> Transportation<o:p></o:p> 2 -4.88 0.823 11 0.114 0 22.2 161 world_phys<a></a> Transportation<o:p></o:p> 3 -9.06 1.55 150 0.114 0 139 300 pixel_phys<a></a> Transportation<o:p></o:p> I guess<a></a> I should<a></a> set some<a></a> actors<a></a>, but I do not find<a></a> any<a></a> clear<a></a> examples<a></a> in the documentation. <o:p></o:p> <a></a>Thanks for your<a></a> answers<a></a>/help, <o:p> </o:p> <o:p> Cheers<a></a>, </o:p> <o:p>Maximilien </o:p> <o:p></o:p> </div> # " Ce courriel et les documents qui lui sont joints peuvent contenir des informations confidentielles, être soumis aux règlementations relatives au contrôle des exportations ou ayant un caractère privé. 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