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Prompt Events
Single
event
●
single photon is counted by detector (1-10%)
True
coincidence
●
event derives from single positron-electron
annihilation
●
both photons reach tomograph without
interaction
Random
coincidence
●
two nuclei decay at approximately the same
time
●
random event count rate (R
ab
) between two
detectors
a
and
b
:
2
2
N NN R
b a
ab
∝ ⋅
=
τ
ESTRO Teaching Course Advanced Imaging: PET – Basic Principles
25