[Gate-users] Problems with scoring edep and dose in non rectangular geometries and CAD geometries

Wed Oct 10 16:21:29 CEST 2018

Hi Leonie,

it is strange that for the sphere works fine and not for the cylinder. Do
you have a way to check if your mesh has holes?
Freecad for example when you charge a mesh tells you that the mesh has
defects.

Sorry I go again with the possibility that the position is not exactly the
same, if you are working with a narrow proton beam, which not cover totally
the mesh, the error can be big. If it is the case I would suggest to
validate the mesh Vs normal-volume with a broad beam that cover and more
the volume, of with small mesh structures.

Best regards
Maikol

El mié., 10 oct. 2018 a las 14:32, Leonie Brodbek (<
leonie.brodbek at uni-oldenburg.de>) escribió:

>
> Hi all,
>
>
> we tried again to play around with the mesh structure but that did not
> change the results.
>
> We changed the resolution of the mesh structure from 12 to 432 facets for
> a  box geometry of 1 cm x 1 cm x 0.5 cm.
>
> In our opinion, for a box geometry the mesh resolution will not have an
> impact so that is also what we expected.
>
>
> Furthermore we scored a sphere with R = 0.25 mm in a waterphantom in a
> proton beam and get good results comparable to yours. When we score in a
> cylinder, we get for the Gate geometry twice the value of the CAD geometry.
> We will keep on searching for a solution of our problem, if anybody has
> another idea we would be very thankful!
>
> Kind regards
> Leonie
>
>
>
> ------------------------------
> *Von:* Maikol Salas Ramirez <mmsalas at gmail.com>
> *Gesendet:* Montag, 8. Oktober 2018 15:21:29
> *An:* Leonie Brodbek
> *Cc:* Maxime Chauvin; gate-users
> *Betreff:* Re: [Gate-users] Problems with scoring edep and dose in non
> rectangular geometries and CAD geometries
>
> Hi all,
>
> I did test (for my, this topic is very important), I put a cylinder
> (H=1mm, R=0.25mm) and a sphere (R=0.25mm) in a Lu-177 box 1m3 (images
> attached). The result are consistent:
>
> S-Value (mGy/Mbq-s)
> Geometry Cylinder (bone) Background (source) Sphere (fat)
> Solid 9,07 0,01 10,18
> Mesh 8,87 0,01 9,96
> %Error -2,15 0,70 -2,14
>
> For sure there is a small difference, but it comes from the surface
> triangulation in the mesh.
>
> I calculated the deposited energy by the spectrum.
>
> It will be interesting to see under what conditions there is not
> consistency between the two geometrical approaches.
>
> Best regards
> Maikol
>
> El lun., 8 oct. 2018 a las 13:20, Maikol Salas Ramirez (<mmsalas at gmail.com>)
> escribió:
>
>> Hi Leoni,
>>
>> Just going back to this sentence "When scoring edep we obtain a value of
>> about 3000 MeV in the geometry built with Gate, when scoring in the CAD
>> geometry we obtain a value of about 370 MeV".
>>
>> This difference can come from the "finish" of your mesh, it is important
>> to remember that the mesh representation is not the same that the 3D volume
>> with perfect curves. I would say that it is a good idea to play with the
>> level of detail of the finish of the mesh surfaces. Also depending of the
>> size of your geometries and  if you are simulation electrons, you could
>> have big differences, because electron are very sensible to this surface
>> changes.
>>
>> Best regards
>> Maikol
>>
>> El lun., 8 oct. 2018 a las 12:36, Leonie Brodbek (<
>> leonie.brodbek at uni-oldenburg.de>) escribió:
>>
>>> Dear Maxime,
>>>
>>>
>>> Thank you!
>>>
>>> Unfortunately we already checked this and it seems that both geometries
>>> fit well and that this does not cause the problem.
>>>
>>>
>>> Kind regards
>>>
>>> Leonie
>>> ------------------------------
>>> *Von:* Maxime Chauvin <maxime.chauvin at inserm.fr>
>>> *Gesendet:* Montag, 8. Oktober 2018 12:01:11
>>> *An:* Leonie Brodbek
>>> *Cc:* Elia Alessio; gate-users at lists.opengatecollaboration.org
>>> *Betreff:* Re: [Gate-users] Problems with scoring edep and dose in non
>>> rectangular geometries and CAD geometries
>>>
>>> Dear Léonie,
>>>
>>> something you could check is the position of the geometry. Importing a
>>> .stl file can result in a unwanted shift due to a different reference frame
>>> from CAD compared to how GATE build a box or a cylinder. And this can cause
>>> a difference in Edep and absorbed dose.
>>>
>>> As a rough check you can use the visualisation (Gate --qt) to see if
>>> your geometries are identical between your 2 simulations.
>>>
>>> Kind regards,
>>>   Maxime Chauvin
>>>
>>> On 8 Oct 2018, at 11:26, Leonie Brodbek <leonie.brodbek at uni-oldenburg.de>
>>> wrote:
>>>
>>> Hi Alessio,
>>>
>>> thanks a  lot!
>>>
>>> We tried to create geometries with a CAD program to import more complex
>>> geometries and tested it with scoring in a box that is built inside Gate
>>> and with the same geometry built in the CAD program.
>>> When scoring edep we obtain a value of about 3000 MeV in the geometry
>>> built with Gate, when scoring in the CAD geometry we obtain a value of
>>> about 370 MeV. We imported the CAD geometries via a .stl file and the
>>> insert specification "tessellated". We obtained the same behavior when
>>> scoring Edep in cylinders built in gate and with the help of a CAD programm.
>>>
>>>
>>> Kind regards
>>> Leonie
>>>
>>> ------------------------------
>>> *Von:* Elia Alessio <alessio.elia at medaustron.at>
>>> *Gesendet:* Montag, 8. Oktober 2018 10:58:37
>>> *An:* Leonie Brodbek
>>> *Cc:* gate-users at lists.opengatecollaboration.org
>>> *Betreff:* RE: Problems with scoring edep and dose in non rectangular
>>> geometries and CAD geometries
>>>
>>> Hi Leonie,
>>>
>>> thanks for your email. Concerning the first point you spotted could you
>>> be more precise? (for example what do you mean with “different results with
>>> different order of magnitude”?). With respect to the second point, this is
>>> a known behavior of the dose actor. At the moment, it cannot handle
>>> correctly non-regular geometries as far as I know. I would recommend you to
>>> work with the edep and then post-process the dose.
>>>
>>> Hope it can help!
>>>
>>> Best
>>> Alessio
>>>
>>> *From:* Gate-users [
>>> mailto:gate-users-bounces at lists.opengatecollaboration.org
>>> <gate-users-bounces at lists.opengatecollaboration.org>] *On Behalf Of *Leonie
>>> Brodbek
>>> *Sent:* Montag, 08. Oktober 2018 10:31
>>> *To:* Gate-users at lists.opengatecollaboration.org
>>> *Subject:* [Gate-users] Problems with scoring edep and dose in non
>>> rectangular geometries and CAD geometries
>>>
>>> Dear all,
>>>
>>> we try to perform simulations of different detectors with Gate and have
>>> some problems when scoring dose and edep in different volumes, perhaps
>>> anyone can help us with these issues:
>>>
>>> - When we score dose and edep in a gate constructed geometry and in the
>>> same CAD geometry we obtain different results with different orders of
>>> magnitude (even in rectangular geometries).
>>>
>>> - When we score dose and edep in non rectangular geometries we cannot
>>> recalculate the dose out of edep and it seems that the dose in Gate is
>>> calculated by a geometry surrounding the real geometry but having
>>> rectangular corners, e.g. for a sphere of radius 0.5 cm the dose can be
>>> recalculated out of edep  by a cube with side length 1 cm.
>>>
>>> We would be very thankful for any help!
>>>
>>> Kind regards
>>> Leonie Brodbek
>>> *Disclaimer:*
>>> Please notice our E-Mail Disclaimer
>>> http://www.medaustron.at/email-disclaimer/
>>>
>>> _______________________________________________
>>> Gate-users mailing list
>>> Gate-users at lists.opengatecollaboration.org
>>> http://lists.opengatecollaboration.org/mailman/listinfo/gate-users
>>>
>>>
>>> _______________________________________________
>>> 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/20181010/8b9c9128/attachment-0001.html>