[Gate-users] Overlap between scanner geometry and Voxellized phantom

[Simon Stute]

Hi Bosky,

We encountered exactly the same problem and the problem comes from Geant4.
As I know the particles are "born" in a certain volume (here the phantom)
and they move to a second volume only when they reach a boundary of the
first one, so even if the particles are both in the phantom (i.e. first
volume) and the second one (overlapping, here your scanner), they behave as
they are in the first one. And unfortunately there is no solution ... except
to resize your phantom if it's possible ...

Cheers,
Simon

On Thu, May 15, 2008 at 5:14 PM, Ravindranath, Bosky <bosky at bnl.gov> wrote:

> Hello Gate users,
>
> I'm using voxellized phantoms to test my scanner performance, however due
> to the positioning of the scanner, there is bound to be overlapping regions
> between the scanner and the image that is read in as the phantom. The
> regions in the phantom that overlap with the scanner has material properties
> set to vacuum. When I run my simulations, I do not see any gamma
> interactions with the overlapping detector regions. Is there a way to work
> around this? I tried to define the scanner as a daughter of the phantom,
> GATE did not allow me to do that (I set the type as parameterized box
> matrix), I tried defining the phantom first and then the geometry, but the
> result was the same.
>
> Any suggestions appreciated.
> Thank you,
> Bosky
>
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