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<p class="MsoNormal">To continue what I have found – <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The correct dose is not simply dividing by the total number of voxels in the doseActor. In fact, I have to divide by the total number of voxels in the union of the doseActor and the geometry volume its attached to.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">For instance, if I make my cube of water 100mm on a side, but make the doseActor 125mm on a side, I will only register dose within the volume of the cube. This makes sense – I should register zero dose for those voxels outside of the water
cube.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">However, during dose calculation, the doseActor multiplies by the number of voxels that fell within the water cube. When using complex geometry from STL files, I can’t know this number.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">It seems the calculation would be fine if the doseActor is contained completely within your geometry, but how can you encompass an entire geometry (say, a liver organ modeled in STL) using the rectangular solid doseActor? I can’t know exactly
how many doseActor voxels actually fall within the liver.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>From:</b> Josh Knowland <br>
<b>Sent:</b> Tuesday, January 15, 2019 11:06 AM<br>
<b>To:</b> 'gate-users@lists.opengatecollaboration.org' <gate-users@lists.opengatecollaboration.org><br>
<b>Subject:</b> RE: Dose Actor Voxels?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Sorry, I had a typo. I meant:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l2 level1 lfo3">Dose from doseActor seems to always
<b>multiply</b> by the number of doseActor voxels. If I sum the dose output and then
<b>divide</b> by the number of voxels, I get the same as if I calculate dose from Edep.<o:p></o:p></li></ul>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>From:</b> Gate-users <<a href="mailto:gate-users-bounces@lists.opengatecollaboration.org">gate-users-bounces@lists.opengatecollaboration.org</a>>
<b>On Behalf Of </b>Josh Knowland<br>
<b>Sent:</b> Tuesday, January 15, 2019 11:03 AM<br>
<b>To:</b> <a href="mailto:gate-users@lists.opengatecollaboration.org">gate-users@lists.opengatecollaboration.org</a><br>
<b>Subject:</b> Re: [Gate-users] Dose Actor Voxels?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hi Matthew, thank you for the reply.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Here is what I have done to try to verify the calculations:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l2 level1 lfo3">Simulation of 1 liter of water hit with F18 positrons.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l2 level1 lfo3">Calculated dose three ways:
<o:p></o:p>
<ul style="margin-top:0in" type="circle">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l2 level2 lfo3">Summing Edep from Singles output and converting to Gray.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l2 level2 lfo3">Summing Edep from doseActor and converting to Gray.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l2 level2 lfo3">Summing dose from doseActor (already Gray).<o:p></o:p></li></ul>
</li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l2 level1 lfo3">Edep from Singles and summed Edep from doseActor always agree.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l2 level1 lfo3">Dose from doseActor seems to always divided by the number of doseActor voxels. If I sum the dose output and then multiply by the number of voxels, I get the same as if I calculate
dose from Edep.<o:p></o:p></li></ul>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Can anyone explain this? When the dose map is already divided by voxel, why can’t I just sum all the voxels? I get the same results using VolumeWeighting or MassWeighting (of course, I’m using 1 liter of water, so that’s the same.)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thank you all,<o:p></o:p></p>
<p class="MsoNormal">Josh<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b>From:</b> Matthew Strugari <<a href="mailto:matthew.strugari@dal.ca">matthew.strugari@dal.ca</a>>
<br>
<b>Sent:</b> Tuesday, January 15, 2019 10:22 AM<br>
<b>To:</b> Josh Knowland <<a href="mailto:jknowland@lucernodynamics.com">jknowland@lucernodynamics.com</a>>;
<a href="mailto:gate-users@lists.opengatecollaboration.org">gate-users@lists.opengatecollaboration.org</a><br>
<b>Subject:</b> Re: Dose Actor Voxels?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<div id="divtagdefaultwrapper">
<p><span style="font-size:12.0pt;color:black">Hi Josh,<o:p></o:p></span></p>
<p><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
<p><span style="font-size:12.0pt;color:black">I am not entirely familiar on the behaviour of the doseActor, but it appears that the output dose is given as the dose per voxel. Hence, the same dose is deposited after integration in each case.<o:p></o:p></span></p>
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<div id="divtagdefaultwrapper">
<p style="background:white"><span style="font-size:12.0pt;color:black"><br>
Matthew<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="color:black">From:</span></b><span style="color:black"> Gate-users <<a href="mailto:gate-users-bounces@lists.opengatecollaboration.org">gate-users-bounces@lists.opengatecollaboration.org</a>> on behalf of Josh Knowland <<a href="mailto:jknowland@lucernodynamics.com">jknowland@lucernodynamics.com</a>><br>
<b>Sent:</b> January 14, 2019 2:53:48 PM<br>
<b>To:</b> <a href="mailto:gate-users@lists.opengatecollaboration.org">gate-users@lists.opengatecollaboration.org</a><br>
<b>Subject:</b> [Gate-users] Dose Actor Voxels?</span> <o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="xmsonormal">All,<o:p></o:p></p>
<p class="xmsonormal"> <o:p></o:p></p>
<p class="xmsonormal">Can you explain how the voxel size and number impacts the calculated dose by the doseActor?<o:p></o:p></p>
<p class="xmsonormal">I have simulated a 1 liter cube of water containing 0.01 mCi of 18F positrons. When I enable the doseActor using 1000 voxels each 1cm^3, I get a total of
<b><span style="color:black">2.43E-05 Gy.</span></b><span style="color:black"> However, if I enable the doseActor using only 1 voxel of size 10cm^3, I get a dose of
<b>2.43E-02 Gy.</b> </span><o:p></o:p></p>
<p class="xmsonormal"><span style="color:black"> </span><o:p></o:p></p>
<p class="xmsonormal"><span style="color:black">I get the same total energy deposited no matter the voxel size and number, why not dose?</span><o:p></o:p></p>
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