<s>
18F-FMISO	O
or	O
fluoromisonidazole	B-Application
is	O
a	O
radiopharmaceutical	B-Algorithm
used	O
for	O
PET	B-Application
imaging	I-Application
of	O
hypoxia	O
.	O
</s>
<s>
FMISO	B-Application
was	O
one	O
of	O
the	O
first	O
such	O
agents	O
,	O
after	O
initial	O
synthesis	O
in	O
the	O
late	O
1980s	O
.	O
</s>
<s>
On	O
entering	O
a	O
viable	O
cell	O
,	O
the	O
nitro	O
group	O
of	O
the	O
FMISO	B-Application
nitroimidazole	O
is	O
reduced	O
.	O
</s>
<s>
In	O
non-hypoxic	O
cells	O
,	O
the	O
reduced	O
FMISO	B-Application
molecule	O
can	O
be	O
oxidised	O
,	O
and	O
therefore	O
diffuses	O
out	O
of	O
the	O
cell	O
to	O
circulate	O
freely	O
and	O
ultimately	O
be	O
excreted	O
.	O
</s>
<s>
In	O
hypoxic	O
tumour	O
cells	O
however	O
this	O
oxidation	O
cannot	O
take	O
place	O
and	O
the	O
FMISO	B-Application
molecules	O
accumulate	O
.	O
</s>
<s>
Their	O
location	O
can	O
then	O
be	O
quantitatively	O
imaged	O
using	O
positron	B-Application
emission	I-Application
tomography	I-Application
.	O
</s>
<s>
Large	O
scale	O
clinical	O
trials	O
with	O
FMISO	B-Application
have	O
not	O
been	O
carried	O
out	O
,	O
however	O
there	O
is	O
some	O
evidence	O
from	O
small-scale	O
early-stage	O
imaging	O
trials	O
that	O
PET-measured	O
hypoxia	O
(	O
using	O
FMISO	B-Application
,	O
and	O
the	O
alternative	O
radiotracer	O
FAZA	O
)	O
is	O
linked	O
to	O
overall	O
survival	O
and	O
loco-regional	O
control	O
in	O
head	O
and	O
neck	O
cancer	O
patients	O
.	O
</s>
<s>
Despite	O
some	O
positive	O
early	O
results	O
further	O
research	O
is	O
required	O
to	O
characterise	O
the	O
specificity	O
and	O
sensitivity	O
of	O
FMISO	B-Application
,	O
and	O
exactly	O
how	O
hypoxia	O
levels	O
should	O
influence	O
treatment	O
planning	O
decisions	O
.	O
</s>
<s>
FMISO	B-Application
has	O
had	O
limited	O
interest	O
for	O
this	O
purpose	O
,	O
in	O
part	O
due	O
to	O
low	O
target-to-background	O
contrast	O
and	O
long	O
injection	O
to	O
imaging	O
delays	O
(	O
due	O
to	O
slow	O
blood	O
clearance	O
)	O
requiring	O
high	O
injected	O
activities	O
.	O
</s>
