[Gate-users] Brachytherapy cut-off energy

[Maikol Salas Ramirez]

Hi Alexandre

Look like 0.1 cm is the equivalent distance for your tissue  (here is
important that you follow the tissue composition that describe the AAPM
43), if you set this distance for photons in the setcutregion option, it
means that after this equivalent energy (as you wrote 5keV) the simulation
is not going to create any new secondary particle, and the photon will
interact directly and deposit his last 5keV.

I am not sure if you need this energy filter, if you fix it in 5keV, you
probably are losing this energy, I mean last 5keV of each photon that will
deposit directly.

Geant4 energy deposit algorithm is made to deposit all the energy, but it
avoit the secondary production after this energy to prevent divergence.

I hope someone else say something to be sure about, otherwise you can also
ask on the Geant4 mail-list.

Best regards
Maikol

El El lun, 7 may 2018 a las 21:55, <xela.errac at gmail.com> escribió:

> Thank you for you reply Maikol, But that's exactly one of my questions
> about choosing the right method in Gate.
> Do I have to adjust for each material, the distance (SetCutInRegion) to
> always get this cut in energy of 5 keV or used an energy filter ?
>
> The energy cut-off is defined as follows :
> “The energy cutoff, is intended to exclude low-energy or contaminant
> photons (e.g., characteristic x-rays originating in the outer layers of
> steel or titanium source cladding) that increase air Kerma rate without
> contributing significantly to dose at distances greater than 0.1 cm in tis-
> sue. The value of the energy cuttoff is typically 5 keV for low-energy
> photon”
>
> Best regards,
>
> Alexandre
>
> Le 7 mai 2018 à 14:47, Maikol Salas Ramirez <mmsalas at gmail.com> a écrit :
>
> Hi Alexandre
>
> I think the cut off is represented by the in Gate by the Production
> threshold, in Geant4 intead of energy you have to specify a distance for
> the particle that you are interested.
>
> http://wiki.opengatecollaboration.org/index.php/Users_Guide:Cut_and_Variance_Reduction_Technics
>
> Otherwise you can play with a energy killer.
>
> It depends of the your definition of cut-off.
>
> Best regards
> Maikol
>
> 2018-05-07 14:23 GMT+02:00 Alexandre CARRÉ <xela.errac at gmail.com>:
>
>> In the AAPM 43, they specified a cut off in energy at 5 keV. How can i
>> reproduce this cut off in Gate ?
>>
>> Best regards,
>>
>> Alexandre
>>
>> _______________________________________________
>> 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/20180507/e46ca94a/attachment-0001.html>