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Forum: Medical Applications
Re: Question some mistake in PDD curve only in the build-up region (Jaafar EL Bakkali)
Date: 22 Jun, 2012
From: Youming Yang <Youming Yang>

Could you give more details such as:

How is your geometry/scoring set up? Is it a homogenous phantom in vacuum or air? Build-up dose can be heavily influenced by contamination electrons from outside the phantom, so if you are comparing you want to make sure your entire geometry is correct, even outside of the phantom. (Additionally, if your geometry has discrete intersections or slabs, it could be a boundary crossing issue.)

Which physics package are you using? In my experience, the "Standard EM" physics package does not perform as well as the Livermore LowE EM package in certain situations. (This is the second most likely the issue)

Finally, what is your source? If you have an unfiltered spectrum vs. a filtered spectrum, you might see convergence deeper in the phantom due to beam hardening, but have differences in the buildup. (This one is somewhat unlikely, as it would require quite a non-negligible fractional fluence of lowE photons in the spectrum)

Ming

On Thu, 14 Jun 2012 21:21:04 GMT, Jaafar EL Bakkali wrote:

> Hi everyone, i'm using Geant4 code to simulate a medical accelerator ,
> the output is a text file that contains :the voxels IDs and the Dose in
> each voxel . when i'm doing the comparaison between my results and those
> comes from experimental ,i get more than 20% error in buil-up region
> ,but in the rest region the dose is converged to the experimental data.
> any idea,how can i solve this problem. Best Regards.

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1 None: Re: some mistake in PDD curve only in the build-up region   (Jaafar EL Bakkali - 22 Jun, 2012)
(_ None: Re: some mistake in PDD curve only in the build-up region   (Youming Yang - 23 Jun, 2012)
(_ None: Re: some mistake in PDD curve only in the build-up region   (Jaafar EL Bakkali - 24 Jun, 2012)
(_ None: Re: some mistake in PDD curve only in the build-up region   (Youming Yang - 24 Jun, 2012)
(_ None: Re: some mistake in PDD curve only in the build-up region   (Jaafar EL Bakkali - 24 Jun, 2012)
(_ None: Re: some mistake in PDD curve only in the build-up region   (Youming Yang - 24 Jun, 2012)
(_ None: Re: some mistake in PDD curve only in the build-up region   (Jaafar EL Bakkali - 26 Jun, 2012)
(_ None: Re: some mistake in PDD curve only in the build-up region   (Youming Yang - 01 Jul, 2012)
(_ None: Re: some mistake in PDD curve only in the build-up region   (Jaafar EL Bakkali - 03 Jul, 2012)
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