[Gate-users] S-Values and DoseActor issues (Nicollas Goncalves Cavedini)

Wed Oct 19 23:28:32 CEST 2022

Hi Sophia!

Firstly, thanks for your detailed answer to my questions! About the "Ion
Source", this publication by Julia Brosch is the same that I read. I was
hoping that the people working in GATE development know if this bug was
corrected.

About the Edep and S-Values, I was using the organ's mass and Edep for the
dose calculation but how can I calculate the S-value? Should I get the
division of the dose by the accumulated activity and later divide it by the
number of primaries (/gate/application/setTotalNumberOfPrimaries)?

I greatly appreciate your help!

*Best regards,*

*Nícollas Gonçalves Cavedini*
BSc in Physics - PUCRS
M. Eng. in Electrical Engineering - PUCRS
PhD student in Biomedical Gerontology - PUCRS

Medical Image Computing Laboratory (MEDICOM)
Contact: +55 (51) 99922-9957
Porto Alegre, Brazil.

Em qua., 19 de out. de 2022 às 11:18, Sophia Pells <
sophia.pells at manchester.ac.uk> escreveu:

> Hi Nícollas,
>
> I've calculated S-factors for Lu-177 in Gatev8.2 before so I will have a
> go at answering your questions:
>
> 1) Is the "Ion Source" recommended for this?
> There have been reported issues with the ion source for Lu-177 in some
> versions of Geant4, particularly v10.5.0 (see
> http://lists.opengatecollaboration.org/pipermail/gate-users/2019-November/011175.html).
> It may have been fixed in later versions but I would still recommend using
> a UserSpectrum and defining the source yourself so you know exactly what
> photon, beta, mono-energetic electron data is being used (the
> mono-energetic electron emission energies and intensities especially vary
> quite a bit with different data sources).
>
> 2) ) Is the "DoseActor" the best way to record the dose?
> I used the DoseActor, but found the Edep output was more useful than the
> Dose output (for my applications) . This gives the energy deposited in
> each voxel (in MeV). It can be enabled with the commands:
>
> /gate/actor/NAME/enableEdep             true
> /gate/actor/NAME/enableUncertaintyEdep  true
>
> Note that the uncertainty is *relative*.
>
> 3) How do I calculate the S-values?
> The Edep output gives the energy deposited in each voxel of the image. I
> would use a set of VOIs and ImageJ to get the total energy deposited in
> each organ (sum over the slices) and use that with the organ mass to
> calculate the dose and S-factors.  I had to run each source organ as a
> separate simulation due to memory limitations and then sum the contribution
> from each source region for each target region. I would recommend avoiding
> the particleFilter actor as I got some weird results with this (they might
> have been fixed since I used it). I would just run separate simulations to
> get the separate contribution from photons, betas etc.
>
> OpenDose is a great resource for S-factors. I validated my simulations by
> downloading the ICRP 110 AF phantom and comparing my S-factors with the
> ones on OpenDose.
> https://www.opendose.org/svalues
>
> Hope this helps!
>
> Best wishes,
>
> Sophia
>
> ------------------------------
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>    1. S-Values and DoseActor issues (Nicollas Goncalves Cavedini)
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> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 18 Oct 2022 08:31:29 -0300
> From: Nicollas Goncalves Cavedini <nicollas.cavedini at acad.pucrs.br>
> To: gate-users <Gate-users at lists.opengatecollaboration.org>
> Subject: [Gate-users] S-Values and DoseActor issues
> Message-ID:
>         <CAMTcvva3g8_War69zqXf=
> JTT7CBUo77VTXsmWgitpz7Nywfv+A at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Dear GATE Users, I am sending this email again as I have not received a
> response.
>
> I am working on my PhD project with PET/CT images of prostate cancer and I
> have some questions about anthropomorphic phantom simulations. I intend to
> perform simulations with 177Lu using the "Golem" phantom from GSF Family.
>
> My questions are:
> 1) Is the "Ion Source" recommended for this?
>
> 2) Is the "DoseActor" the best way to record the dose? I was searching in
> the previous e-mails and I have found a report that the DoseActor may not
> be the most suitable resource for this application.
>
> 3) How do I calculate the S-values? For each simulation, I get the absorbed
> dose in each organ, but how do I "transform" this into S-values? We have
> PET images with 4 time points after the injection and I can extract the
> accumulated activity (Ã).
>
> Any help is appreciated!
>
> *Atenciosamente,*
>
> *Nícollas Gonçalves Cavedini*
> BSc in Physics - PUCRS
> M. Eng. in Electrical Engineering - PUCRS
> PhD student in Biomedical Gerontology - PUCRS
>
> Medical Image Computing Laboratory (MEDICOM)
> Contact: +55 (51) 99922-9957
> Porto Alegre, Brazil.
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