[Gate-users] Potential bug report of Edep in DoseActor (Edep always == 1 Mev for any Ion)

[Albert Grace Lieu]

Hi Loïc,

Thank you very much for actively answering DoseActor related questions in
the past ten years. I saw your answers in the GATE archive quite often. I
did read through almost all example codes in GATE-RTiON, but I did not find
the example where DoseActor is used to record energy deposited by ions for
dosimetry.

Here is the problem I have found with Edep in DoseActor, a similar question
<http://lists.opengatecollaboration.org/pipermail/gate-users/2009-July/003406.html>
was also asked many years ago. No matter what source I use, like I-131,
Lu-177, Edep in DoseActor always returns *1 (Mev) per disintegration*. Dose
in DoseActor also utilizes the value returned Edep, which leads to a wrong
result. I would rather believe that I made a mistake somewhere than think
GATE's DoseActor failed in my case.

Could you or any other GATE user have a look at my code? It is
self-containt code. You will finish the entire verification in less than 5
minutes. Here is what the GATE code does:

   - Phantom: 101*101*101 voxelized tissue ( water equivalent) phantom,
   with a side of 2 mm for each voxel
   - Source: 10 mm radius sphere voxelized Lu177 source with a side of 2 mm
   for each voxel, and being placed in the center of the phantom
   - DoseActor: record dose, Edep, and export a mass image of the phantom
   (all 3D array)
   - ProductionAndStoppingActor: record the number of Lu177 generated in
   each voxel, indicated by Lu177-Stop (3D array)

        According to the user manual, "The unit of edep is MeV and the unit
of dose is Gy".


You will also find a python script (result-analysis.ipynb) to do the
analysis:


   - reads dose, edep, mass, and particle-prod
   - calculate the average energy deposited by a single disintegration.

Thank you very much for any help and verification.

Albert








On Fri, Mar 5, 2021 at 12:48 AM Grevillot Loic <loic.grevillot at medaustron.at>
wrote:

> FYI,
>
> DoseActor validation tests were provided for the GATE-RTiON
> <https://gate.uca.fr/download/gate-rtion> release, in the context of
> light ion beam therapy under the gitcontrib
> <https://github.com/OpenGATE/GateContrib/tree/master/GATE-RTion>
> repository.
>
> The tests can be applied in principle to any GATE release and may help you
> as a starting point.
>
> It would be nice to increase the collection of tests for other clinical
> applications such as  yours!
>
>
>
> Best,
>
> Loïc
>
>
>
>
>
>
>
> *From:* Gate-users [mailto:
> gate-users-bounces at lists.opengatecollaboration.org] *On Behalf Of *Albert
> Grace Lieu
> *Sent:* Freitag, 5. März 2021 05:59
> *To:* gate-users <gate-users at lists.opengatecollaboration.org>
> *Subject:* [Gate-users] Edep returned by DoseActor is about 7 times
> bigger then hand calculated value
>
>
>
> Hi Gate users,
>
>
>
> I am validating the validity of DoseActor in GATE for
> radionuclide dosimetry application. Surprisingly, I found the Edep returned
> by DoseActor is about 7 times bigger than my hand calculated value, so does
> the dose returned by DoseActor. I could be wrong, but I double-checked
> everything I did and had been as prudent as I can before asking for
> suggestions here.
>
>
>
> Here is what I did in GATE:
>
>    - Phantom: 101*101*101 voxelized tissue ( water equivalent) phantom,
>    with a side of 2 mm for each voxel
>    - Source: 10 mm radius sphere voxelized Lu177 source with a side of 2
>    mm for each voxel, and being placed in the center of the phantom
>    - DoseActor: record dose, Edep, and export a mass image of the phantom
>    (all 3D array)
>    - ProductionAndStoppingActor: record the number of Lu177 generated in
>    each voxel, indicated by Lu177-Stop (3D array)
>
>         According to the user manual, "The unit of edep is MeV and the
> unit of dose is Gy".
>
>
>
> Here is how I calculate the average of the energy of Lu177 in water, Lu177
> is a beta emitter, the range of electron in water is way smaller than 2mm,
> thus it is stopped where is created. Given the branching ratio of Lu177, on
> average a single Lu177 disintegration would deposit 134.16 Kev (electrons
> only) or 162.95 Kev (electrons and gammas).
>
>
>
> [image: RTEmagicC_Lu-177_decays.png.png]
>
>
>
> However, when I divide Edep by Lu177-Stop, the energy per Lu177
> disintegration returned by DoseActor is ~1.0 Mev, which 7 times bigger
> than my hand calculated value. Is this an internal issue? I attach my Gate
> code for your review.
>
>
>
>
>
> Thanks a lot for your help.
>
> Sincere wishes,
>
> Stay safe and healthy
>
> Albert
>
>
>
>
>
> *Disclaimer:*
> Please notice our E-Mail Disclaimer
> http://www.medaustron.at/email-disclaimer/
>
>
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