[Gate-users] Dose Actor - Problem with 3D vs 1D

[Hermann Fuchs]

Dear Loic

It seems you are correct.
In our initial analysis we underestimated the influence of multiple
scattering.
Integrating of the dose yields the correct result.

Thank you for clarifying,
Hermann
On Mon, 2011-07-25 at 15:29 +0200, Loic Grevillot wrote:
> Dear Hermann,
> 
> The blue curve, that you call "strange Bragg peak" looks like a dose
> along the beam axis (along the beam axis for a single spot you have
> this behavior due to multiple Coulomb scattering: no transversal
> charge equilibrium).
> In contrary, what you call "normal Bragg peak" is an integrated
> depth-dose profile (1D).
> If you use a 3D resolution, you have to integrate the dose in each
> plan in order to recalculate the integrated depth-dose profile (1D).
> I made similar tests and it works for me.
> 
> 
> 
> Loïc Grevillot, Ph.D. Student
> PARTNER project, CERN
> 
> IBA Particle Therapy / Creatis-LRMN
> Tel (IBA):         +32 10 487 729
> 
> 
> 
> 2011/7/25 Hermann Fuchs <hermann.fuchs at meduniwien.ac.at>
>         Dear Gate users and developers,
>         
>         We are using Gate6.1 (at Med. Univ. Vienna on Ubuntu 11.04
>         with
>         geant4.9.4p01, root 5.30 and at IFIC --Univ. Valencia/CSIC--
>         with
>         geant4.9.4p01, root 5.28) for hadrontherapy simulations.
>         
>         Using the Radiationtherapy Example Novice3, we encountered a
>         strange
>         behavior of the dose actor when using Analyze (.hdr) files. We
>         just
>         modified the Resolution, from
>         
>         /gate/actor/doseDistribution/setResolution         1 1 400
>         
>         (1D case) to
>         
>         /gate/actor/doseDistribution/setResolution         400 400 400
>         
>         (3D case), and the sigma_x and sigma_y of the beam, from 3 to
>         1 mm.
>         
>         In the combination 3D and sigma 1 mm, we have observed a
>         strange Bragg
>         peak (see the blue line in the attachment Nov3_3D_1-mm.png).
>         Using 1D and sigma 1mm the observed Bragg-peak returns to look
>         normal.
>         If we increase the sigma to or above 3 mm, 3D and 1D files
>         look normal
>         too. See attached files Nov3_3D_1-3mmSigma.png (yellow line on
>         the
>         profile) and Nov3_1D_1-3mmSigma.png (both lines).
>         
>         It seems that there is a problem with the dose actor and
>         analyze files
>         (we have not checked whether in the txt-files the problem
>         appears)
>         producing 3D output if the sigma of the beam is small.
>         
>         Can you confirm that?
>         
>         Thank you very much!
>         
>         Best regards,
>         
>         Herman and Irene
>         
>         --
>         -------------
>         DI Hermann Fuchs
>         Div. Medical Radiation Physics
>         Department of Radiotherapy
>         Med. Univ. Vienna / AKH Vienna
>         Währinger Gürtel 18-20
>         A-1090 Wien
>         
>         Tel.  + 43 / 1 / 40 400 7271
>         Mail. hermann.fuchs at meduniwien.ac.at
>         
>         _______________________________________________
>         Gate-users mailing list
>         Gate-users at lists.opengatecollaboration.org
>         http://lists.opengatecollaboration.org/mailman/listinfo/gate-users
> 

-- 
-------------
DI Hermann Fuchs
Div. Medical Radiation Physics
Department of Radiotherapy
Med. Univ. Vienna / AKH Vienna
Währinger Gürtel 18-20
A-1090 Wien

Tel.  + 43 / 1 / 40 400 7271
Mail. hermann.fuchs at meduniwien.ac.at