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

[Stathis Kamperis]

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.