[Gate-users] Dose results interpretation

[Matthew Strugari]

Hi Dmitry,

You can read about the calculation of dose and its uncertainty here<https://opengate.readthedocs.io/en/latest/voxelized_source_and_phantom.html?highlight=dose%20actor#dose-collection>. The number of events required to reach 1% uncertainty is a bit of a loaded question. It will depend on your dose actor resolution and the location of the volume of interest so it may take some trial and error to find a suitable number. I only have dose actor experience working with beta-emitters on the order of a few MeV for which I required 4x10^8 primaries to achieve reasonable uncertainties.

Larger volumes can have lower uncertainty due to containment of more energy-depositing events. Dose voxels near your proton beam will encounter more interactions and lower uncertainty than voxels far from the beam where few interactions occur. Also keep in mind that your voxel size will have an effect on the dose since absorbed dose is calculated as energy deposited per unit mass.

Hope this helps,
Matthew

--
Matthew Strugari
PhD Candidate at Biomedical Translational Imaging Centre - BIOTIC,
5890 University Ave, Halifax, NS, B3K 6R8


From: Gate-users <gate-users-bounces at lists.opengatecollaboration.org> on behalf of Dmitry Hits <dmitry.hits at phys.ethz.ch>
Date: Tuesday, May 11, 2021 at 12:31
To: Gate-Users <gate-users at lists.opengatecollaboration.org>
Subject: [Gate-users] Dose results interpretation
CAUTION: The Sender of this email is not from within Dalhousie.
Hi Gaters,

I am trying to understand results output by the dose actor, which I enabled with the following lines:

/gate/actor/addActor DoseActor             dose5
        /gate/actor/dose5/save                   results/dose_2021May11_171652_5.root
        /gate/actor/dose5/attachTo               box5
        /gate/actor/dose5/stepHitType            random
        /gate/actor/dose5/setResolution          1 10 1
        /gate/actor/dose5/enableDose             true
        /gate/actor/dose5/enableUncertaintyDose  true
        /gate/actor/dose5/enableNumberOfHits     true

The source is a pencil beam of protons of 100 MeV. I simulated 10000 events.

Here is the histogram I got:
[cid:image001.png at 01D74675.94466BC0]

My question is why is the error so large? How is it calculated?

Cheers,

Dmitry

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