[Gate-users] Questions about LET and average LET calculation in Gate
Andreas Resch
andreas.resch at meduniwien.ac.at
Tue Mar 29 11:09:03 CEST 2022
Dear Guangru Li,
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).
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.
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:
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.
best,
Andreas
Am 2022-03-29 02:34, schrieb 李广儒:
> Dear Gate users,
>
> I'm trying to calculate LET and average LET(including dose-average and
> track-average) by Gate. But I met some problems.
>
> First, I found that in the user guide, it says that
>
> "_DoseAveraged (default) or TrackAveraged LET both calculated by using
> the Geant4 EMCalculator method -GetElectronicStoppingPowerDEDX_". But I
> checked the manual of Geant4(Application Developers Guide) and found
> that there is a "_ComputeElectronicDEDX method_" in G4EmCalculator
> class as shown below:
>
> So I think maybe it use _ComputeElectronicDEDX method_ ,not
> _GetElectronicStoppingPowerDEDX_. It maybe a little mistake in the
> manual of Gate in my opinion.
>
> Second, if Gate use _ComputeElectronicDEDX method,_ the LET is
> calculated by kinetic energy of particles as below:
>
> "_Instead of computing the LET as the quotient between the actual
> electronic energy loss and step length_
>
> _computed during the simulation, we calculated the LET of the step,
> Lsn, as the corresponding_
>
> _mean energy loss per unit path length in the material according to the
> proton kinetic energy_
>
> _at the step. In our code, Lsn was obtained with the method
> ComputeElectronicDEDX() of_
>
> _G4EmCalculator class."_
>
> These are indicated in the _Cortés-Giraldo M A and Carabe A 2015 Phys.
> Med. Biol. 60 2645-69_.But I wonder what method was used to calculate
> DoseAveraged and TrackAveraged LET in Gate_._
>
> And it's very confusing to me. Because it also said in the Gate manual
> that if I use parallel computation, there will be _"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."_So why there are 2 outputs?
> And what are physical meanings of _denominator and numerator ?_
>
> HOPE TO GET THE INTERPRETATION OF THESE CONFUSING METHODS. ANY
> SUGGESTIONS AND ANSWERS ARE WELCOMED AND HELPFUL TO ME. THANK YOU IN
> ADVANCE!
>
> Best,
>
> Guangru Li
>
> _______________________________________________
> Gate-users mailing list
> Gate-users at lists.opengatecollaboration.org
> http://lists.opengatecollaboration.org/mailman/listinfo/gate-users
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.opengatecollaboration.org/pipermail/gate-users/attachments/20220329/20c9e4a4/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 8c5ab715.png
Type: image/png
Size: 10376 bytes
Desc: not available
URL: <http://lists.opengatecollaboration.org/pipermail/gate-users/attachments/20220329/20c9e4a4/attachment-0002.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: G4EMcalculator.png
Type: image/png
Size: 277363 bytes
Desc: not available
URL: <http://lists.opengatecollaboration.org/pipermail/gate-users/attachments/20220329/20c9e4a4/attachment-0003.png>
More information about the Gate-users
mailing list