<s>
Magnetic	B-Algorithm
resonance	I-Algorithm
neurography	I-Algorithm
(	O
MRN	O
)	O
is	O
the	O
direct	O
imaging	O
of	O
nerves	O
in	O
the	O
body	O
by	O
optimizing	O
selectivity	O
for	O
unique	O
MRI	O
water	O
properties	O
of	O
nerves	O
.	O
</s>
<s>
Magnetic	B-Algorithm
resonance	I-Algorithm
neurography	I-Algorithm
is	O
used	O
to	O
evaluate	O
major	O
nerve	O
compressions	O
such	O
as	O
those	O
affecting	O
the	O
sciatic	O
nerve	O
(	O
e.g.	O
</s>
<s>
A	O
related	O
technique	O
for	O
imaging	O
neural	O
tracts	O
in	O
the	O
brain	O
and	O
spinal	O
cord	O
is	O
called	O
magnetic	O
resonance	O
tractography	B-Algorithm
or	O
diffusion	B-Algorithm
tensor	I-Algorithm
imaging	I-Algorithm
.	O
</s>
<s>
Magnetic	O
resonance	O
imaging	O
(	O
MRI	O
)	O
is	O
based	O
on	O
differences	O
in	O
the	O
physical	O
properties	O
of	O
protons	B-Application
in	O
water	O
molecules	O
in	O
different	O
tissues	O
in	O
the	O
body	O
.	O
</s>
<s>
The	O
protons	B-Application
and	O
the	O
water	O
molecules	O
of	O
which	O
they	O
are	O
part	O
have	O
subtly	O
different	O
movement	O
characteristics	O
that	O
relate	O
to	O
their	O
biophysical	O
surroundings	O
.	O
</s>
<s>
Diffusion	B-Algorithm
MRI	I-Algorithm
had	O
been	O
developed	O
to	O
take	O
advantage	O
of	O
this	O
phenomenon	O
to	O
show	O
contrast	O
between	O
white	O
matter	O
and	O
grey	O
matter	O
in	O
the	O
brain	O
.	O
</s>
<s>
However	O
,	O
diffusion	B-Algorithm
MRI	I-Algorithm
proved	O
ineffective	O
for	O
imaging	O
of	O
nerves	O
for	O
reasons	O
that	O
were	O
not	O
initially	O
clear	O
.	O
</s>
<s>
Filler	O
and	O
Howe	O
discovered	O
that	O
the	O
problem	O
was	O
that	O
the	O
most	O
of	O
the	O
image	O
signal	O
in	O
nerve	O
came	O
from	O
protons	B-Application
that	O
were	O
not	O
involved	O
in	O
anisotropic	O
diffusion	O
.	O
</s>
<s>
Endoneurial	O
fluid	O
increases	O
when	O
nerve	O
is	O
compressed	O
,	O
irritated	O
or	O
injured	O
,	O
leading	O
to	O
nerve	O
image	O
hyperintensity	O
in	O
an	O
magnetic	B-Algorithm
resonance	I-Algorithm
neurography	I-Algorithm
image	O
.	O
</s>
<s>
Subsequent	O
research	O
has	O
further	O
demonstrated	O
the	O
biophysical	O
basis	O
for	O
the	O
ability	O
of	O
MR	B-Algorithm
Neurography	I-Algorithm
to	O
show	O
nerve	O
injury	O
and	O
irritation	O
.	O
</s>
<s>
Measurements	O
of	O
the	O
T2	O
relaxation	O
rate	O
of	O
nerve	O
by	O
Filler	O
and	O
Howe	O
revealed	O
that	O
previous	O
reports	O
of	O
a	O
short	O
relaxation	O
time	O
were	O
wrong	O
and	O
thatonce	O
signal	O
from	O
lipid	O
protons	B-Application
was	O
suppressedthe	O
primary	O
image	O
signal	O
from	O
nerve	O
had	O
long	O
T2	O
relaxation	O
rates	O
best	O
imaged	O
with	O
pulse	O
sequence	O
echo	O
times	O
in	O
the	O
range	O
of	O
50	O
to	O
100milliseconds	O
.	O
</s>
<s>
In	O
addition	O
,	O
they	O
later	O
showed	O
that	O
T2-neurography	O
differs	O
from	O
most	O
other	O
MR	O
imaging	O
in	O
that	O
the	O
conspicuity	O
or	O
relative	O
prominence	O
of	O
nerve	O
is	O
affected	O
by	O
the	O
angle	O
of	O
voxel	B-Algorithm
orientation	O
during	O
the	O
acquisition	O
of	O
the	O
image	O
.	O
</s>
<s>
When	O
acquisitions	O
are	O
done	O
with	O
echo	O
times	O
below	O
40milliseconds	O
,	O
there	O
can	O
be	O
"	O
magic	O
angle	O
effects	O
"	O
that	O
provide	O
some	O
spurious	O
information	O
,	O
so	O
MR	B-Algorithm
Neurography	I-Algorithm
is	O
always	O
done	O
with	O
echo	O
times	O
greater	O
than	O
40milliseconds	O
.	O
</s>
<s>
Within	O
a	O
few	O
months	O
of	O
the	O
initial	O
findings	O
on	O
diffusion-based	O
nerve	O
imaging	O
,	O
the	O
diffusion	O
technique	O
for	O
nerve	O
imaging	O
was	O
adapted	O
to	O
permit	O
for	O
visualization	O
of	O
neural	O
tracts	O
in	O
the	O
spinal	O
cord	O
and	O
brain	O
via	O
Diffusion	B-Algorithm
Tensor	I-Algorithm
Imaging	I-Algorithm
.	O
</s>
<s>
The	O
most	O
significant	O
impact	O
of	O
magnetic	B-Algorithm
resonance	I-Algorithm
neurography	I-Algorithm
is	O
on	O
the	O
evaluation	O
of	O
the	O
large	O
proximal	O
nerve	O
elements	O
such	O
as	O
the	O
brachial	O
plexus	O
(	O
the	O
nerves	O
between	O
the	O
cervical	O
spine	O
and	O
the	O
underarm	O
that	O
innervate	O
shoulder	O
,	O
arm	O
and	O
hand	O
)	O
,	O
the	O
lumbosacral	O
plexus	O
(	O
nerves	O
between	O
the	O
lumbosacral	O
spine	O
and	O
legs	O
)	O
,	O
the	O
sciatic	O
nerve	O
in	O
the	O
pelvis	O
,	O
as	O
well	O
as	O
other	O
nerves	O
such	O
as	O
the	O
pudendal	O
nerve	O
that	O
follow	O
deep	O
or	O
complex	O
courses	O
.	O
</s>
<s>
Magnetic	B-Algorithm
resonance	I-Algorithm
neurography	I-Algorithm
has	O
greatly	O
expanded	O
the	O
efficacy	O
of	O
nerve	O
diagnosis	O
by	O
allowing	O
uniform	O
evaluation	O
of	O
virtually	O
any	O
nerve	O
in	O
the	O
body	O
.	O
</s>
<s>
There	O
are	O
numerous	O
reports	O
dealing	O
with	O
specialized	O
uses	O
of	O
magnetic	B-Algorithm
resonance	I-Algorithm
neurography	I-Algorithm
for	O
nerve	O
pathology	O
such	O
as	O
traumatic	O
brachial	O
plexus	O
root	O
avulsions	O
,	O
cervical	O
radiculopathy	O
,	O
guidance	O
for	O
nerve	O
blocks	O
,	O
demonstration	O
of	O
cysts	O
in	O
nerves	O
,	O
carpal	O
tunnel	O
syndrome	O
,	O
and	O
obstetrical	O
brachial	O
plexus	O
palsy	O
.	O
</s>
<s>
In	O
addition	O
several	O
formal	O
large	O
scale	O
outcome	O
trials	O
carried	O
out	O
with	O
high	O
quality	O
"	O
Class	O
A	O
"	O
methodology	O
have	O
been	O
published	O
that	O
have	O
verified	O
the	O
clinical	O
efficacy	O
and	O
validity	O
of	O
MR	B-Algorithm
Neurography	I-Algorithm
.	O
</s>
<s>
Use	O
of	O
magnetic	B-Algorithm
resonance	I-Algorithm
neurography	I-Algorithm
is	O
increasing	O
in	O
neurology	O
and	O
neurosurgery	O
as	O
the	O
implications	O
of	O
its	O
value	O
in	O
diagnosing	O
various	O
causes	O
of	O
sciatica	O
becomes	O
more	O
widespread	O
.	O
</s>
<s>
Recent	O
patent	O
litigation	O
concerning	O
MR	B-Algorithm
Neurography	I-Algorithm
has	O
led	O
some	O
unlicensed	O
centers	O
to	O
discontinue	O
offering	O
the	O
technique	O
.	O
</s>
<s>
Magnetic	B-Algorithm
resonance	I-Algorithm
neurography	I-Algorithm
does	O
not	O
pose	O
any	O
diagnostic	O
disadvantage	O
relative	O
to	O
standard	O
magnetic	O
resonance	O
imaging	O
because	O
neurography	O
studies	O
typically	O
include	O
high	O
resolution	O
standard	O
MRI	O
image	O
series	O
for	O
anatomical	O
reference	O
along	O
with	O
the	O
neurographic	O
sequences	O
.	O
</s>
<s>
Magnetic	B-Algorithm
resonance	I-Algorithm
neurography	I-Algorithm
can	O
only	O
be	O
performed	O
in	O
1.5	O
tesla	O
and	O
3	O
tesla	O
cylindrical	O
type	O
scanners	O
and	O
ca	O
n't	O
really	O
be	O
done	O
effectively	O
in	O
lower	O
power	O
"	O
open	O
"	O
MR	O
scanners	O
-	O
this	O
can	O
pose	O
significant	O
challenges	O
for	O
claustrophobic	O
patients	O
.	O
</s>
