<s>
[18F]Fluorodeoxyglucose	O
(	O
INN	O
)	O
,	O
or	O
fluorodeoxyglucose	B-Application
F	O
18	O
(	O
USAN	O
and	O
USP	O
)	O
,	O
also	O
commonly	O
called	O
fluorodeoxyglucose	B-Application
and	O
abbreviated	O
[18F]FDG,	O
2-[18F]FDG	O
or	O
FDG	O
,	O
is	O
a	O
radiopharmaceutical	B-Algorithm
,	O
specifically	O
a	O
radiotracer	O
,	O
used	O
in	O
the	O
medical	B-Application
imaging	I-Application
modality	O
positron	B-Application
emission	I-Application
tomography	I-Application
(	O
PET	O
)	O
.	O
</s>
<s>
After	O
[18F]FDG	O
is	O
injected	O
into	O
a	O
patient	O
,	O
a	O
PET	B-Application
scanner	I-Application
can	O
form	O
two-dimensional	O
or	O
three-dimensional	O
images	O
of	O
the	O
distribution	O
of	O
[18F]FDG	O
within	O
the	O
body	O
.	O
</s>
<s>
Israel	O
's	O
oxygen-18	O
facility	O
had	O
shut	O
down	O
due	O
to	O
the	O
Gulf	B-Application
War	I-Application
,	O
and	O
the	O
U.S.	O
government	O
had	O
shut	O
down	O
its	O
Isotopes	O
of	O
Carbon	O
,	O
Oxygen	O
and	O
Nitrogen	O
facility	O
at	O
Los	O
Alamos	O
National	O
Laboratory	O
,	O
leaving	O
Isotec	O
as	O
the	O
main	O
supplier	O
.	O
</s>
<s>
Cyclotron	O
production	O
of	O
fluorine-18	O
may	O
be	O
accomplished	O
by	O
bombardment	O
of	O
neon-20	O
with	O
deuterons	O
,	O
but	O
usually	O
is	O
done	O
by	O
proton	B-Application
bombardment	O
of	O
18O-enriched	O
water	O
,	O
causing	O
a	O
(	O
p-n	O
)	O
reaction	O
(	O
sometimes	O
called	O
a	O
"	O
knockout	O
reaction	O
"	O
a	O
common	O
type	O
of	O
nuclear	O
reaction	O
with	O
high	O
probability	O
where	O
an	O
incoming	O
proton	B-Application
"	O
knocks	O
out	O
"	O
a	O
neutron	O
)	O
in	O
the	O
18O	O
.	O
</s>
<s>
The	O
109.8-minute	O
half-life	B-Application
of	O
fluorine-18	O
makes	O
rapid	O
and	O
automated	O
chemistry	O
necessary	O
after	O
this	O
point	O
.	O
</s>
<s>
After	O
picking	O
up	O
a	O
proton	B-Application
H+	O
from	O
a	O
hydronium	O
ion	O
in	O
its	O
aqueous	O
environment	O
,	O
the	O
molecule	O
becomes	O
glucose-6-phosphate	O
labeled	O
with	O
harmless	O
nonradioactive	O
"	O
heavy	O
oxygen	O
"	O
in	O
the	O
hydroxyl	O
at	O
the	O
C-2	O
position	O
.	O
</s>
<s>
Although	O
in	O
theory	O
all	O
[18F]FDG	O
is	O
metabolized	O
as	O
above	O
with	O
a	O
radioactivity	O
elimination	O
half-life	B-Application
of	O
110	O
minutes	O
(	O
the	O
same	O
as	O
that	O
of	O
fluorine-18	O
)	O
,	O
clinical	O
studies	O
have	O
shown	O
that	O
the	O
radioactivity	O
of	O
[18F]FDG	O
partitions	O
into	O
two	O
major	O
fractions	O
.	O
</s>
<s>
About	O
75%	O
of	O
the	O
fluorine-18	O
activity	O
remains	O
in	O
tissues	O
and	O
is	O
eliminated	O
with	O
a	O
half-life	B-Application
of	O
110	O
minutes	O
,	O
presumably	O
by	O
decaying	O
in	O
place	O
to	O
O-18	O
to	O
form	O
[18O]O-glucose-6-phosphate,	O
which	O
is	O
non-radioactive	O
(	O
this	O
molecule	O
can	O
soon	O
be	O
metabolized	O
to	O
carbon	O
dioxide	O
and	O
water	O
,	O
after	O
nuclear	O
transmutation	O
of	O
the	O
fluorine	O
to	O
oxygen	O
ceases	O
to	O
prevent	O
metabolism	O
)	O
.	O
</s>
<s>
Another	O
fraction	O
of	O
[18F]FDG,	O
representing	O
about	O
20%	O
of	O
the	O
total	O
fluorine-18	O
activity	O
of	O
an	O
injection	O
,	O
is	O
excreted	O
renally	O
by	O
two	O
hours	O
after	O
a	O
dose	O
of	O
[18F]FDG,	O
with	O
a	O
rapid	O
half-life	B-Application
of	O
about	O
16	O
minutes	O
(	O
this	O
portion	O
makes	O
the	O
renal-collecting	O
system	O
and	O
bladder	O
prominent	O
in	O
a	O
normal	O
PET	B-Application
scan	I-Application
)	O
.	O
</s>
<s>
This	O
short	O
biological	O
half-life	B-Application
indicates	O
that	O
this	O
20%	O
portion	O
of	O
the	O
total	O
fluorine-18	O
tracer	O
activity	O
is	O
eliminated	O
renally	O
much	O
more	O
quickly	O
than	O
the	O
isotope	O
itself	O
can	O
decay	O
.	O
</s>
<s>
Because	O
of	O
this	O
rapidly	O
excreted	O
urine	O
18F	O
,	O
the	O
urine	O
of	O
a	O
patient	O
undergoing	O
a	O
PET	B-Application
scan	I-Application
may	O
therefore	O
be	O
especially	O
radioactive	O
for	O
several	O
hours	O
after	O
administration	O
of	O
the	O
isotope	O
.	O
</s>
<s>
All	O
radioactivity	O
of	O
[18F]FDG,	O
both	O
the	O
20%	O
which	O
is	O
rapidly	O
excreted	O
in	O
the	O
first	O
several	O
hours	O
of	O
urine	O
which	O
is	O
made	O
after	O
the	O
exam	O
,	O
and	O
the	O
80%	O
which	O
remains	O
in	O
the	O
patient	O
,	O
decays	O
with	O
a	O
half-life	B-Application
of	O
110	O
minutes	O
(	O
just	O
under	O
two	O
hours	O
)	O
.	O
</s>
<s>
Thus	O
,	O
within	O
24	O
hours	O
(	O
13	O
half-lives	B-Application
after	O
the	O
injection	O
)	O
,	O
the	O
radioactivity	O
in	O
the	O
patient	O
and	O
in	O
any	O
initially	O
voided	O
urine	O
which	O
may	O
have	O
contaminated	O
bedding	O
or	O
objects	O
after	O
the	O
PET	O
exam	O
will	O
have	O
decayed	O
to	O
2−13	O
=	O
of	O
the	O
initial	O
radioactivity	O
of	O
the	O
dose	O
.	O
</s>
<s>
In	O
practice	O
,	O
patients	O
who	O
have	O
been	O
injected	O
with	O
[18F]FDG	O
are	O
told	O
to	O
avoid	O
the	O
close	O
vicinity	O
of	O
especially	O
radiation-sensitive	O
persons	O
,	O
such	O
as	O
infants	O
,	O
children	O
and	O
pregnant	O
women	O
,	O
for	O
at	O
least	O
12	O
hours	O
(	O
7	O
half-lives	B-Application
,	O
or	O
decay	O
to	O
the	O
initial	O
radioactive	O
dose	O
)	O
.	O
</s>
<s>
The	O
labeled	O
[18F]FDG	O
compound	O
has	O
a	O
relatively	O
short	O
shelf	O
life	O
which	O
is	O
dominated	O
by	O
the	O
physical	O
decay	O
of	O
fluorine-18	O
with	O
a	O
half-life	B-Application
of	O
109.8	O
minutes	O
,	O
or	O
slightly	O
less	O
than	O
two	O
hours	O
.	O
</s>
<s>
Still	O
,	O
this	O
half	B-Application
life	I-Application
is	O
sufficiently	O
long	O
to	O
allow	O
shipping	O
the	O
compound	O
to	O
remote	O
PET	O
scanning	O
facilities	O
,	O
in	O
contrast	O
to	O
other	O
medical	O
radioisotopes	O
like	O
carbon-11	O
.	O
</s>
<s>
Recently	O
,	O
on-site	O
cyclotrons	O
with	O
integral	O
shielding	O
and	O
portable	O
chemistry	O
stations	O
for	O
making	O
[18F]FDG	O
have	O
accompanied	O
PET	B-Application
scanners	I-Application
to	O
remote	O
hospitals	O
.	O
</s>
<s>
In	O
PET	B-Application
imaging	I-Application
,	O
[18F]FDG	O
is	O
primarily	O
used	O
for	O
imaging	O
tumors	O
in	O
oncology	O
,	O
where	O
a	O
static	O
[18F]FDG	O
PET	B-Application
scan	I-Application
is	O
performed	O
and	O
the	O
tumor	O
[18F]FDG	O
uptake	O
is	O
analyzed	O
in	O
terms	O
of	O
Standardized	B-Algorithm
Uptake	I-Algorithm
Value	I-Algorithm
(	O
SUV	B-Algorithm
)	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
FDG-PET	B-Application
can	O
be	O
used	O
for	O
diagnosis	O
,	O
staging	O
,	O
and	O
monitoring	O
treatment	O
of	O
cancers	O
,	O
particularly	O
in	O
Hodgkin	O
's	O
disease	O
,	O
non-Hodgkin	O
lymphoma	O
,	O
colorectal	O
cancer	O
,	O
breast	O
cancer	O
,	O
melanoma	O
,	O
and	O
lung	O
cancer	O
.	O
</s>
<s>
Then	O
,	O
the	O
patient	O
is	O
placed	O
in	O
the	O
PET	B-Application
scanner	I-Application
for	O
a	O
series	O
of	O
one	O
or	O
more	O
scans	O
which	O
may	O
take	O
from	O
20	O
minutes	O
to	O
as	O
long	O
as	O
an	O
hour	O
(	O
often	O
,	O
only	O
about	O
one-quarter	O
of	O
the	O
body	O
length	O
may	O
be	O
imaged	O
at	O
a	O
time	O
)	O
.	O
</s>
