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

[Faical Alaoui-Abdalaoui-Slimani]

Dear David,

I appreciate your help and assistance. Thank you very much for this useful explanations.
I have one and last question :)
 As you say  "...The images which contain "only the spatial distribution" are actually already given in Gray (J/kg)... ". Please How can I associate for each intensity in the image (HU) to the absorbed dose in Gray (J/kg)?


BIG Thx
Faical

-----Original Message-----
From: Gate-users [mailto:gate-users-bounces at lists.opengatecollaboration.org] On Behalf Of David Boersma
Sent: Thursday, October 05, 2017 6:18 AM
To: gate-users at lists.opengatecollaboration.org
Subject: Re: [Gate-users] Absorbed dose only In VOI's

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,
>>
>>
>>
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