[Gate-users] about attenuation and sensitivity in GATE

[Bjoern Jakoby]

Hello Hongwei,

the sensitivity for the ECAT 962 HR+ was measured as 6650 cps/MBq 
(center FOV) and 7180 cps/MBq (10 cm off-center FOV) according to NEMA 
NU2-2001.
Hope this helps,
Bjoern

Hongwei Ye wrote:
>
> Dear All,
>
> I'm wondering if there is any way to turn off the attenuation in GATE 
> (because I'd like to use a simulation without attenuation in 
> reconstruction).
>
> What I did right now is to use "Air" to replace "Water" (or something 
> else) for the object material. But I met a problem here:
>
> I have tested two simulations: same objects with same activity, same 
> scan time, but simulation 1 is made by "Air" and simulation 2 is made 
> by "Water". Guess what I got? Simulation 2 (13920 counts) had more 
> coincidences than simulation 1 (8646 counts) even if simulation 2 was 
> supposed to be attenuated more by water. (I attached .mac file here)
>
> Can anyone explain this phenomena or guide me how to turn off the 
> attenuation ? Should I use "Vacuum" instead of "Air" and set up "back 
> to back gamma source"?
>
> One more question is about the sensitivity: what is its range for ECAT 
> 962 system? By roughly calculating, I got 20~50 cps/kBq depending on 
> different objects. It seems to me those number are too high.
>
> Thanks a lot.
>
> Regards,
> Hongwei
>
>
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