[Gate-users] Absorbed dose only In VOI's

[David Boersma]

Dear Faical,

It all depends on what you put and what you try to get out of it. :)

If I understand your question (1) correctly, you would like to get some 
kind of absolute calibration. Unfortunately I have no clue what your 
dose figure is displaying.

Typically the number Nprim of primaries is orders of magnitude lower 
than the number Nreal of particles emitted in the real setup. The images 
which contain "only the spatial distribution" are actually already given 
in Gray (J/kg), but because Nprim is much lower than Nreal, the values 
you see for the dose seem extremely low. You need to multiply this 
distribution with a scale factor, basically with Nreal/Nprim. It's 
basically *your* job to figure out how to compute this factor.

One way to do it is that you use the details of your setup including 
calibration information of the treatment devices to compute "Nreal". 
Since "Nprim" is a number that you choose yourself in your simulation, 
you then have the correct scaling factor.

If you do not really have the ambition to do an absolute calibration 
then you could maybe just assume a certain dose level at a particular 
point (or an average dose in a particular region), and then the ratio of 
that assumed/prescribed dose and the dose that you actually find for 
that point (or region) in your simulation could be used as the overall 
scaling factor for the whole distribution.

I think I do not understand question (2). In my own work, we do not give 
a single dose number for the whole ROI (or "VOI" as you call it), but 
instead we summarize the dose distribution as a "dose volume histogram", 
which is basically a reverse cumulative histogram of the dose values in 
all voxels within the ROI. There is AFAIK not a tool built-in to Gate to 
produce this. And as already stated before, I very much doubt whether I 
interpret your intended meaning of "the cumulated dose in this VOI" 
correctly.


Disclaimer: I may be completely wrong here in my interpretations of your 
questions. If I accidentally wrote something useful then that is nice. I 
think that it would be good to talk directly with your supervisor or 
other local expert in your own lab or research institute, about the 
dosimetry aspect of your small animal setup and how to relate that to 
your simulation.

Good luck,
David B.


Den 05/10/2017 kl. 02:07, skrev Faical Alaoui-Abdalaoui-Slimani:
> Dear David,
> 
> Thank you very much for your replay.
> In my simulation I'm using "DoseActor" to builds 3D images of the energy (edep) and dose deposited in a given volume.
> 
> /gate/actor/addActor                               DoseActor  doseDistribution
> /gate/actor/doseDistribution/enableEdep     true
> /gate/actor/doseDistribution/enableDose     true
> ...
> 
> In the result I get the 3D image see attached File "Dose Actors.png". (With 1 to 6 represent generator of photons)
> 1- Please, How can I calculate the deposit Dose in mGy of each voxels because in my case i get only the  spatial distribution of the dose ?
> 2- I draw the VOI with matlab script and I'm interested in the cumulated dose in this VOI.  the Analyze file is used as input in the simulation (*.hdr/*.img).
> Is there any  method to do it directly with Gate ?
> 
> 
> Thank you very much for your time.
> Best Regards,
> 
> -----Original Message-----
> From: Gate-users [mailto:gate-users-bounces at lists.opengatecollaboration.org] On Behalf Of David Boersma
> Sent: Wednesday, October 04, 2017 4:35 AM
> To: gate-users at lists.opengatecollaboration.org
> Subject: Re: [Gate-users] Absorbed dose only In VOI's
> 
> Dear Faical,
> 
> I think that this is usually done with external data analysis tools. The technical details depend on how your VOIs are stored & specified, and what exactly you mean by "the resulting dose". There *may* be some convenient tools/scripts that do something similar to what you want to achieve, but you need to be careful to check that it is indeed doing exactly what you want.
> 
> E.g. in my own work I also get voxelized dose distributions. I am a fan of python, so I do all my analysis with python scripts. For my case, the ROIs are specified as a set of curves that are stored in a DICOM file.
> My scripts then find all voxels that are within the curves, with some policy for dealing with voxels that are only partly within a curve.
> Etcetera. Other people would maybe do this in matlab, Octave, or a research version of a TPS.
> 
> David
> 
> 
> 
> Den 01/10/2017 kl. 17:22, skrev Faical Alaoui-Abdalaoui-Slimani:
>> Dear all,
>>
>> I have currently been using the DoseActor attached to a Digital mouse
>> phantom to find the absorbed dose in each voxels.
>>
>> I simulated different tumors and I'm interested in the resulting dose
>> per specified VOI's.
>>
>> please how can i attach a dose actor to each VOI's ?
>>
>> Thank you very much for your time.
>>
>> --
>>
>> Best Regards,
>>
>>
>>
>> _______________________________________________
>> 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
>