[Gate-users] variance in the number of optical photons produced per gamma interaction in PET

[Vesna Cuplov]

Hi Pedro,

Yes, when the gamma photon deposits 0.511 MeV in your LYSO crystal, then
the number of emitted optical photons would be 0.511x28000 with a standard
deviation of resolution_scale x sqrt{0.511x28000}. Could you send your
geometry, materials and root file?

thank you
vesna



On Tue, Apr 15, 2014 at 2:42 PM, Pedro Correia <pmcorreia at ua.pt> wrote:

> Dear Gate users
>
> I’m simulating a cylindrical Pet, where my crystals are LYSO, with a light
> yield of 28000 photons/MeV, each one with ~ 3eV, and my source are gamma
> rays with fixed energy of 511 keV.
>
> When I analise the root files, I saw that the actual number of hits of
> each detected interaction of 511 keV is not ~14000, as I would expect since
> 28000*0.511=14308. Actually, what I see in the root file is that some
> events produced ~10000 hits, while others produced ~15000.
>
> Is this related with the random seed that I’m using for simulations? In my
> point of view, the number of hits per each gamma photon absorbed should be
> the same, for the same energy, am I wrong?
>
> I can attach the root output if someone ask to.
> Thank you all. Best regards.
>
> Pedro Correia
> PhD student
> University of Aveiro
>
>
>
>
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