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

[Loic Grevillot]

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
>