[Gate-users] ARF example characteristics

[Saeed Heidary]

Dear GATE users
I am simulating SPECT and I have a lot of difficulties.
These obstacles mostly due to the amount of activity and probably the
incapability of my computer to track the
photons in collimator.
I am going to utilize ARF(Angular Response Function) method and ARF example
in GATE
I have few questions in ARF example in GATE specially the reason of
choosing some quantities ;

Firstly,the activity mentioned in two mac files in ARF simulation?
I mean 1 MBq in generateARFdate.mac and 26.666.666 Bq in useARFTables.mac
or if they are choosen deliberately,it is necessary to adjust any special
ratio between two quantitise ?

Secondly, the dimensions of the gamma source mentioned in
generateARFdata.mac(halfx=2 cm and halfy=1.cm)!

Thirdly the different dimensions of two SPECTheads in generateARFdate.mac
and useARFTables.mac files.

Fourthly ,Has any body used this example before,If so, its my pleasure to
have his/her experience.
I will be appreciated if somebody help me.

Many thanks