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

[Hermann Fuchs]

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
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