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<p><span style="font-family: 'Times New Roman'; font-size: 14px;">Dear Guangru Li,</span></p>
<p>thank you for carefully reading the Gate documentation. Indeed, the user manual was not consistent and up to date. I just changed it (you can look at it in the pull request now, or in the official documentation in some days).</p>
<p>1. It is computeElectronicDEDX ; note that the restricted LET calculation option, which the second sentence referred to, is now removed in the documentation as this implementation is not sufficiently validated. </p>
<p>2. Parallel computation: If you only simulate on a single CPU you do not need to worry about it. However, if you split your simulation into several simulations I would recommend the following. Looking at the formula for e.g. dose averaged LET:</p>
<p><img src="cid:8c5ab715d95c3da286d758f652def035@meduniwien.ac.at" width="184" height="113" /></p>
<p> let's assume this is the sum over all contributions and Ld = n/d. Now this shall now be randomly subdivided into j computations, the numerator would look like n = n1 + n2 + ... nj and d correspondingly. Ld = (n1 + n2 + ... ) / (d1 + d2 + ...); Therefore, the LET actor allows you to score the numerator and denominator of this equation separately.</p>
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<p>best,</p>
<p>Andreas</p>
<p id="reply-intro">Am 2022-03-29 02:34, schrieb 李广儒:</p>
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<p class="v1MsoNormal"><span style="font-family: 'Times New Roman'; font-size: 14px;">Dear Gate users,</span></p>
<p class="v1MsoNormal"><span style="font-family: 'Times New Roman'; font-size: 14px;">I'm trying to calculate LET and average LET(including dose-average and track-average) by Gate. But I met some problems.</span></p>
<p class="v1MsoNormal"> </p>
<p class="v1MsoNormal"><strong><span style="font-family: 'Times New Roman'; font-size: 14px;">First,</span></strong><span style="font-family: 'Times New Roman'; font-size: 14px;"> I found that in the user guide, it says that</span></p>
<p class="v1MsoNormal"><span style="font-family: 'Times New Roman'; font-size: 14px;">"</span><em><span style="font-family: 'Times New Roman'; font-size: 14px;">DoseAveraged (default) or TrackAveraged LET both calculated by using the Geant4 EMCalculator method -GetElectronicStoppingPowerDEDX</span></em><span style="font-family: 'Times New Roman'; font-size: 14px;">". But I checked the manual of Geant4(Application Developers Guide) and found that there is a "</span><em><span style="font-family: 'Times New Roman'; font-size: 14px;">ComputeElectronicDEDX method</span></em><span style="font-family: 'Times New Roman'; font-size: 14px;">" in G4EmCalculator class as shown below:</span></p>
<p class="v1MsoNormal"><span style="font-family: 'Times New Roman'; font-size: 14px;"><img src="cid:16485449436242ccaf9c24e787255708@meduniwien.ac.at" /><br /></span></p>
<p class="v1MsoNormal"> </p>
<p class="v1MsoNormal"><span style="font-family: 'Times New Roman'; font-size: 14px;">So I think maybe it use </span><em><span style="font-family: 'Times New Roman'; font-size: 14px;">ComputeElectronicDEDX method</span></em><span style="font-family: 'Times New Roman'; font-size: 14px;"> ,not </span><em><span style="font-family: 'Times New Roman'; font-size: 14px;">GetElectronicStoppingPowerDEDX</span></em><span style="font-family: 'Times New Roman'; font-size: 14px;">. It maybe a little mistake in the manual of Gate in my opinion.</span></p>
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<p class="v1MsoNormal"><strong><span style="font-family: 'Times New Roman'; font-size: 14px;">Second, </span></strong><span style="font-family: 'Times New Roman'; font-size: 14px;">if Gate use </span><em><span style="font-family: 'Times New Roman'; font-size: 14px;">ComputeElectronicDEDX method,</span></em><span style="font-family: 'Times New Roman'; font-size: 14px;"> the LET is calculated by kinetic energy of particles as below:</span></p>
<p class="v1MsoNormal"><span style="font-family: 'Times New Roman'; font-size: 14px;">"</span><em><span style="font-family: 'Times New Roman'; font-size: 14px;">Instead of computing the LET as the quotient between the actual electronic energy loss and step length</span></em></p>
<p class="v1MsoNormal"><em><span style="font-family: 'Times New Roman'; font-size: 14px;">computed during the simulation, we calculated the LET of the step, L</span><sub><span style="font-family: 'Times New Roman'; font-size: 14px;">sn</span></sub><span style="font-family: 'Times New Roman'; font-size: 14px;">, as the corresponding</span></em></p>
<p class="v1MsoNormal"><em><span style="font-family: 'Times New Roman'; font-size: 14px;">mean energy loss per unit path length in the material according to the proton kinetic energy</span></em></p>
<p class="v1MsoNormal"><em><span style="font-family: 'Times New Roman'; font-size: 14px;">at the step. In our code, L</span><sub><span style="font-family: 'Times New Roman'; font-size: 14px;">sn</span></sub><span style="font-family: 'Times New Roman'; font-size: 14px;"> was obtained with the method ComputeElectronicDEDX() of</span></em></p>
<p class="v1MsoNormal"><em><span style="font-family: 'Times New Roman'; font-size: 14px;">G4EmCalculator class."</span></em></p>
<p class="v1MsoNormal"><span style="font-family: 'Times New Roman'; font-size: 14px;">These are indicated in the </span><em><span style="font-family: 'Times New Roman'; font-size: 14px;">Cortés-Giraldo M A and Carabe A 2015 Phys. Med. Biol. </span><strong><span style="font-family: 'Times New Roman'; font-size: 14px;">60</span></strong><span style="font-family: 'Times New Roman'; font-size: 14px;"> 2645–69</span></em><span style="font-family: 'Times New Roman'; font-size: 14px;">.But I wonder what method was used to calculate DoseAveraged and TrackAveraged LET in Gate</span><em><span style="font-family: 'Times New Roman'; font-size: 14px;">.</span></em></p>
<p class="v1MsoNormal"><span style="font-family: 'Times New Roman'; font-size: 14px;">And it's very confusing to me. Because it also said in the Gate manual that if I use parallel computation, there will be </span><em><span style="font-family: 'Times New Roman'; font-size: 14px;">"2 output images for each LET actor and run, a file labeled as '-numerator' and one labeled as '-denominator'. Building the quotient of these two images results in the averaged LET image. Note that the numerator and denominator images have to be summed up before the division."</span></em><span style="font-family: 'Times New Roman'; font-size: 14px;">So why there are 2 outputs? And what are physical meanings of </span><em><span style="font-family: 'Times New Roman'; font-size: 14px;">denominator and numerator ?</span></em></p>
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<h2 style="margin-left: 0cm; background: #FCFCFE;"><span style="font-family: 'Times New Roman'; font-size: 14px;"><strong>Hope to get the </strong></span><span class="v1keyword" style="font-family: 'Times New Roman'; font-size: 14px;"><strong>interpretation of these confusing methods. Any suggestions and answers are welcomed and helpful to me. Thank you in advance!</strong></span></h2>
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<p class="v1MsoNormal"><span style="font-family: 'Times New Roman'; font-size: 14px;">Best,</span></p>
<p class="v1MsoNormal"><span style="font-family: 'Times New Roman'; font-size: 14px;">Guangru Li</span></p>
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