[Gate-users] Unrealistic value of max dose with photon beams and a water phantom

[Stathis Kamperis]

Dear Loïc,

thank you for taking the time to clear a major misunderstanding I had
all this time! It suddenly all makes sense now.

Best regards,
Stathis

On Wed, Mar 5, 2014 at 8:32 AM, Grevillot Loic
<loic.grevillot at medaustron.at> wrote:
> Dear Stathis,
>
> Your problem does not come from Gate according to your macro, but from Medical Physics terminology misunderstanding...
> Let's take the example of a 6 MeV photon beam:
> A 6 MeV photon beam corresponds to a beam of electrons accelerated at an energy of 6 MeV, which then interacts in a tungsten target (usually) in order to produce photon due to Bremsstrahlung process. The head of the accelerator is also a complex part that need to be modeled. The mean photon energy is around 1 MeV and is not at all mono-energetic!
>
> Please look at the papers cited in the Gate website (http://www.opengatecollaboration.org/OpenGATEpublications), with validated accelerator models for electrons, photons, protons...
>
> Kind regards,
>
> Loïc Grevillot
>
>
>
>
> -----Original Message-----
> From: gate-users-bounces at lists.opengatecollaboration.org [mailto:gate-users-bounces at lists.opengatecollaboration.org] On Behalf Of Stathis Kamperis
> Sent: Dienstag, 4. März 2014 16:08
> To: gate-users
> Subject: Re: [Gate-users] Unrealistic value of max dose with photon beams and a water phantom
>
> Oops, I forgot to link to my .mac file here:
>
> http://dl.dropboxusercontent.com/u/25202446/photons.mac
>
> Best regards,
> Stathis
>
> On Tue, Mar 4, 2014 at 5:06 PM, Stathis Kamperis <ekamperi at gmail.com> wrote:
>> Hello again folks,
>>
>> if I have a water tank 50x50x50 cm and I attach a dose actor to it and
>> the resolution of the dose actor is 1 1 50 and the beam comes along
>> the z-axis, doesn't that mean that 1 unit in my dose actor corresponds
>> to 1 cm of depth ?
>>
>> Here is a plot with 6, 15, 18, 25 MeV beams from a 10x10cm^2 field at
>> SSD=100cm. The depth of maximum dose is wayyy off compared to the
>> values in my books. I understand that I'm not simulating the whole
>> head of the linear accelerator, but aren't the values awfully out of
>> scale? 3cm for 6 MeV ?  8cm for 18 MeV ?
>>
>> I'd *really* appreciate any insight. I'm using Gate for my thesis and
>> unless I give a very very good explanation why those values are so
>> much off scale or even better fix the problem, I'll have to use some
>> other software :(
>>
>> Best regards,
>> Stathis
>>
>> http://dl.dropboxusercontent.com/u/25202446/photon-dose-depth.png
>>
>>
>> On Tue, Jan 28, 2014 at 10:07 PM, Stathis Kamperis <ekamperi at gmail.com> wrote:
>>> Dear GATE users,
>>>
>>> I'd like to reproduce the plot at the 5th page of the following presentation:
>>>
>>> http://www.opengatecollaboration.org/sites/opengatecollaboration.org/
>>> files/Talk9-GATE_RT.pdf
>>>
>>> I'm using the benchRT/gamma.mac as the basis of my experiments. I
>>> have
>>> 2 questions so far:
>>>
>>> 1. Why do I get my dose max at ~8.5cm of depth, instead of a much
>>> smaller depth as shown in the presentation ?
>>> (I've added: /gate/actor/doseDistribution/enableDose true to
>>> gamma.mac)
>>>
>>> 2. Why even though I add:
>>> /gate/actor/doseDistribution/normaliseDose true
>>>
>>> I still get unnormalized values of dose?
>>>
>>> Best regards,
>>> Stathis
>>>
>>> P.S. Sorry for my naive questions; I'm just getting started.
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