
67-11Medical Imaging
predicted from linear response. At suciently high event rates, the measured count rate actually can
de
crease
wi
th
in
creasing
ph
oton
ev
ent
ra
te
an
d
ev
entually
ca
n
be ex
tinguished
wh
en
im
aging
ra
dioac-
tive
so
urces
of su
ciently
hi
gh
ac
tivities
.
67.6 Positron Emission Tomography
Positron emission tomography (PET) involves a physiological administration of a positron-emitting
ra
diopharmaceutical
in
to
th
e
hu
man
bo
dy
. e pr
incipal
ad
vantage
of PE
T
ov
er
sin
gle-photon
im
aging
is th
e
av
ailability
of a nu
mber
of ph
ysiologically
re
levant
ra
diotracers
th
at
ar
e
la
beled
wi
th
th
e
sh
ort-
lived
po
sitron-emitting
ra
dionuclides
11
C (T
1/2
= ...