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Count Rate Performance
Ratio Trues/Randoms unbalanced for high Activities
Processing of detected photons takes finite time
Noise Equivalent Count Rate:
fR ST
T
NECR
2
2
T
: trues
S
: scattered
R
: randoms
f
: rel. area of
object on
proj. surface
ESTRO Teaching Course Advanced Imaging: PET – Basic Principles
26
Count rate curves for
true, random and
multiple coincidences.
Derived curves for
expected and noise
equivalent count rate
[2]. Data recorded on a
CTI ECAT 953B PET
using a
11
C-filled
cylinder in water.
Noisy image
Maximum
image
quality
Low image
contrast