[Gate-users] how to define an ideal detector or crystal to stop the photon at the surface

[Simon Stute]

Hi,

I think the suggestion of Yuxuan is not so bad, you can define your own
material with almost an infinite density.
The gamma entering the crystal will do several scatter but as closed to the
point it entered as your density is almost infinity.
This method is tricky because you will lose CPU time doing this scatter
interactions, but I don't think a simpler method exists.

Cheers,
Simon

On Tue, Nov 10, 2009 at 10:41 PM, C C <phasenew at hotmail.com> wrote:

>
> Hi, Yuxuan, thanks a lot for suggestion. I am using low energy of only 38
> keV and unfortunately my goal is to study the scatters in phantom. So any
> deviation caused by the detector is significant because of the low counts of
> scattered photons.
> I did try your suggestion by using different detector materials such as:
> Ge, W, Pb, etc. While the primary photon count profile is improved, the
> scattered photons, ie the Compton scatted photons is over-counted in the
> central area of the beam direction because of the scattering in the crystal.
>
> congwu
>
>
>
> > From: yuxuan.zhang at mdanderson.org
> > To: phasenew at hotmail.com
> > Date: Tue, 10 Nov 2009 11:15:31 -0600
> > Subject: RE: [Gate-users] how to define an ideal detector or crystal to
> stop the photon at the surface
> >
> > How about define the material as Lead or Tungsten? And, if you don't care
> the scattering inside
> > the phantom, using very low energy gamma source, such as 50-100 keV. Most
> the photons will stop
> > immediately inside the detectors that is very close to the surface.
> >
> > Yuxuan
> >
> > ________________________________________
> > From: gate-users-bounces at lists.healthgrid.org [
> gate-users-bounces at lists.healthgrid.org] On Behalf Of C C [
> phasenew at hotmail.com]
> > Sent: Tuesday, November 10, 2009 11:00 AM
> > To: gate-users at lists.healthgrid.org
> > Subject: [Gate-users] how to define an ideal detector or crystal to stop
> the photon at the surface
> >
> > Hello, everyone, by searching the archive I found the similar questions
> asked several years ago but not answered. so I bring it out again although
> it may sounds a dumb one.
> >
> > In my application, I do not want simulate the detector. What I want is to
> count the photons at the detector position. If I define a concrete detector
> made of certain material, such as silicon or NaI, some of the photons will
> be dislocated from their entrance position at the detector due to the
> scatters in the detector material. So the question is how to define the
> detector or an ideal material so that the photon can be deposited completely
> as soon as it hit the very surface of the detector? Or can it be done in a
> difference way?
> >
> > Thank you very much for any suggestion.
> >
> > congwu
> >
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