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Hi N<span style="font-family:"Segoe UI", "Segoe UI Web (West European)", "Segoe UI", -apple-system, BlinkMacSystemFont, Roboto, "Helvetica Neue", sans-serif;font-size:14.6667px;background-color:rgb(255, 255, 255);display:inline !important" class="ContentPasted7">í</span>collas, </div>
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I've calculated S-factors for Lu-177 in Gatev8.2 before so I will have a go at answering your questions: </div>
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<div>1<span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">) Is the "Ion Source" recommended for this?</span><br>
</div>
<div class="elementToProof"><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">There have been reported issues with the ion source for Lu-177 in some versions of Geant4, particularly v10.5.0 (see </span><a href="http://lists.opengatecollaboration.org/pipermail/gate-users/2019-November/011175.html"><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">http://lists.opengatecollaboration.org/pipermail/gate-users/2019-November/011175.html</span></a><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">).
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). </span></div>
<div><br>
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<div class="elementToProof"><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">2)</span><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"> </span><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">)
Is the "DoseActor" the best way to record the dose?</span><br>
</div>
<div class="elementToProof"><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">I used the DoseActor, but found the Edep output was more useful than the Dose output
<span style="background-color:rgb(255, 255, 255);display:inline !important" class="ContentPasted6">
(for my applications)<span class="ContentPasted6"> </span></span>. This gives the energy deposited in each voxel (in MeV). It can be enabled with the commands:</span></div>
<div><br>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">/gate/actor/NAME/enableEdep true</span></div>
<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">/gate/actor/NAME/enableUncertaintyEdep true</span><br>
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<div><br>
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<div class="elementToProof"><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Note that the uncertainty is
</span><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"><b>relative</b></span><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">. </span></div>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">3) How do I calculate the S-values?</span><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"> </span><br>
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<div class="elementToProof"><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);" class="ContentPasted9">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. </span></div>
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<div class="elementToProof" style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
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. </div>
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<a href="https://www.opendose.org/svalues" id="LPNoLPOWALinkPreview">https://www.opendose.org/svalues</a><br>
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<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">Hope this helps! </span><br>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Best wishes, </span></div>
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<div style="" class="elementToProof ContentPasted0">Sophia </div>
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Today's Topics:<br>
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1. S-Values and DoseActor issues (Nicollas Goncalves Cavedini)<br>
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----------------------------------------------------------------------<br>
<br>
Message: 1<br>
Date: Tue, 18 Oct 2022 08:31:29 -0300<br>
From: Nicollas Goncalves Cavedini <nicollas.cavedini@acad.pucrs.br><br>
To: gate-users <Gate-users@lists.opengatecollaboration.org><br>
Subject: [Gate-users] S-Values and DoseActor issues<br>
Message-ID:<br>
<CAMTcvva3g8_War69zqXf=JTT7CBUo77VTXsmWgitpz7Nywfv+A@mail.gmail.com><br>
Content-Type: text/plain; charset="utf-8"<br>
<br>
Dear GATE Users, I am sending this email again as I have not received a<br>
response.<br>
<br>
I am working on my PhD project with PET/CT images of prostate cancer and I<br>
have some questions about anthropomorphic phantom simulations. I intend to<br>
perform simulations with 177Lu using the "Golem" phantom from GSF Family.<br>
<br>
My questions are:<br>
1) Is the "Ion Source" recommended for this?<br>
<br>
2) Is the "DoseActor" the best way to record the dose? I was searching in<br>
the previous e-mails and I have found a report that the DoseActor may not<br>
be the most suitable resource for this application.<br>
<br>
3) How do I calculate the S-values? For each simulation, I get the absorbed<br>
dose in each organ, but how do I "transform" this into S-values? We have<br>
PET images with 4 time points after the injection and I can extract the<br>
accumulated activity (Ã).<br>
<br>
Any help is appreciated!<br>
<br>
*Atenciosamente,*<br>
<br>
*Nícollas Gonçalves Cavedini*<br>
BSc in Physics - PUCRS<br>
M. Eng. in Electrical Engineering - PUCRS<br>
PhD student in Biomedical Gerontology - PUCRS<br>
<br>
Medical Image Computing Laboratory (MEDICOM)<br>
Contact: +55 (51) 99922-9957<br>
Porto Alegre, Brazil.<br>
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