<s>
In	B-Algorithm
vivo	I-Algorithm
magnetic	I-Algorithm
resonance	I-Algorithm
spectroscopy	I-Algorithm
(	O
MRS	O
)	O
is	O
a	O
specialized	O
technique	O
associated	O
with	O
magnetic	O
resonance	O
imaging	O
(	O
MRI	B-Algorithm
)	O
.	O
</s>
<s>
Magnetic	B-Algorithm
resonance	I-Algorithm
spectroscopy	I-Algorithm
(	O
MRS	O
)	O
,	O
also	O
known	O
as	O
nuclear	O
magnetic	O
resonance	O
(	O
NMR	O
)	O
spectroscopy	O
,	O
is	O
a	O
non-invasive	O
,	O
ionizing-radiation-free	O
analytical	O
technique	O
that	O
has	O
been	O
used	O
to	O
study	O
metabolic	O
changes	O
in	O
brain	O
tumors	O
,	O
strokes	O
,	O
seizure	O
disorders	O
,	O
Alzheimer	O
's	O
disease	O
,	O
depression	O
,	O
and	O
other	O
diseases	O
affecting	O
the	O
brain	O
.	O
</s>
<s>
Magnetic	B-Algorithm
resonance	I-Algorithm
spectroscopy	I-Algorithm
is	O
an	O
analytical	O
technique	O
that	O
can	O
be	O
used	O
to	O
complement	O
the	O
more	O
common	O
magnetic	O
resonance	O
imaging	O
(	O
MRI	B-Algorithm
)	O
in	O
the	O
characterization	O
of	O
tissue	O
.	O
</s>
<s>
Both	O
techniques	O
typically	O
acquire	O
signal	O
from	O
hydrogen	O
protons	B-Application
(	O
other	O
endogenous	O
nuclei	O
such	O
as	O
those	O
of	O
Carbon	O
,	O
Nitrogen	O
,	O
and	O
Phosphorus	O
are	O
also	O
used	O
)	O
,	O
but	O
MRI	B-Algorithm
acquires	O
signal	O
primarily	O
from	O
protons	B-Application
which	O
reside	O
within	O
water	O
and	O
fat	O
,	O
which	O
are	O
approximately	O
a	O
thousand	O
times	O
more	O
abundant	O
than	O
the	O
molecules	O
detected	O
with	O
MRS	O
.	O
As	O
a	O
result	O
,	O
MRI	B-Algorithm
often	O
uses	O
the	O
larger	O
available	O
signal	O
to	O
produce	O
very	O
clean	O
2D	O
images	O
,	O
whereas	O
MRS	O
very	O
frequently	O
only	O
acquires	O
signal	O
from	O
a	O
single	O
localized	O
region	O
,	O
referred	O
to	O
as	O
a	O
"	O
voxel	O
"	O
.	O
</s>
<s>
Acquiring	O
an	O
MRS	O
scan	O
is	O
very	O
similar	O
to	O
that	O
of	O
MRI	B-Algorithm
with	O
a	O
few	O
additional	O
steps	O
preceding	O
data	O
acquisition	O
.	O
</s>
<s>
Recent	O
advances	O
allow	O
proton	B-Application
MRS	O
without	O
water	O
suppression	O
.	O
</s>
<s>
The	O
drawbacks	O
of	O
this	O
technique	O
is	O
that	O
having	O
two/three	O
phase	O
encoding	O
directions	O
requires	O
lengthy	O
scan	O
time	O
,	O
and	O
the	O
larger	O
volume	O
of	O
acquisition	O
is	O
more	O
likely	O
to	O
introduce	O
artefacts	O
due	O
to	O
poorer	O
shimming	O
,	O
unsuppressed	O
water	O
,	O
as	O
well	O
as	O
the	O
inherent	O
sinc	B-Algorithm
point-spread-function	O
due	O
to	O
the	O
finite	O
sampling	O
of	O
k-space	O
which	O
results	O
in	O
the	O
signal	O
from	O
one	O
voxel	O
bleeding	O
into	O
all	O
others	O
.	O
</s>
<s>
Similar	O
to	O
MRI	B-Algorithm
,	O
MRS	O
uses	O
pulse	O
sequences	O
to	O
acquire	O
signal	O
from	O
several	O
different	O
molecules	O
to	O
generate	O
a	O
spectra	O
instead	O
of	O
an	O
image	O
.	O
</s>
<s>
Additionally	O
,	O
adiabatic	O
pulses	O
have	O
substantially	O
higher	O
bandwidth	O
,	O
which	O
reduces	O
chemical	O
shift	O
displacement	O
artefact	O
,	O
which	O
is	O
particularly	O
important	O
at	O
high	O
field	O
strengths	O
and	O
when	O
a	O
large	O
range	O
of	O
frequencies	O
are	O
desired	O
to	O
be	O
measured	O
(	O
i.e.	O
,	O
measuring	O
both	O
the	O
signals	O
upfield	O
and	O
downfield	O
of	O
water	O
in	O
proton	B-Application
MRS	O
)	O
.	O
</s>
<s>
SPECIAL	O
consists	O
of	O
a	O
spatially	O
selective	O
pre-excitation	O
inversion	O
pulse	O
(	O
typically	O
AFP	O
)	O
followed	O
by	O
spatially	O
selective	O
excitation	O
and	O
refocusing	O
pulses	O
,	O
both	O
of	O
which	O
are	O
usually	O
SLR	O
or	O
truncated	O
sinc	B-Algorithm
pulses	O
.	O
</s>
<s>
This	O
has	O
been	O
shown	O
to	O
greatly	O
reduce	O
lipid	O
contamination	O
,	O
speculated	O
to	O
have	O
arisen	O
from	O
the	O
interaction	O
between	O
the	O
RF	O
pulse	O
and	O
lipid	O
compartments	O
due	O
to	O
incomplete	O
relaxation	O
,	O
magnetization	B-Algorithm
transfer	I-Algorithm
,	O
or	O
the	O
homonuclear	O
Overhauser	O
effect	O
,	O
although	O
the	O
exact	O
mechanism	O
remains	O
unknown	O
.	O
</s>
<s>
MRS	O
allows	O
doctors	O
and	O
researchers	O
to	O
obtain	O
biochemical	O
information	O
about	O
the	O
tissues	O
of	O
the	O
human	O
body	O
in	O
a	O
non-invasive	O
way	O
(	O
without	O
the	O
need	O
for	O
a	O
biopsy	O
)	O
,	O
whereas	O
MRI	B-Algorithm
only	O
gives	O
them	O
information	O
about	O
the	O
structure	O
of	O
the	O
body	O
(	O
the	O
distribution	O
of	O
water	O
and	O
fat	O
)	O
.	O
</s>
<s>
For	O
example	O
,	O
whereas	O
MRI	B-Algorithm
can	O
be	O
used	O
to	O
assist	O
in	O
the	O
diagnosis	O
of	O
cancer	O
,	O
MRS	O
could	O
potentially	O
be	O
used	O
to	O
assist	O
in	O
information	O
regarding	O
to	O
the	O
aggressiveness	O
of	O
the	O
tumor	O
.	O
</s>
<s>
The	O
most	O
common	O
nuclei	O
to	O
be	O
studied	O
are	O
protons	B-Application
(	O
hydrogen	O
)	O
,	O
phosphorus	O
,	O
carbon	O
,	O
sodium	O
and	O
fluorine	O
.	O
</s>
<s>
Prostate	O
cancer	O
:	O
Combined	O
with	O
a	O
magnetic	O
resonance	O
imaging	O
(	O
MRI	B-Algorithm
)	O
and	O
given	O
equal	O
results	O
,	O
then	O
the	O
three-dimensional	O
MRS	O
can	O
predict	O
the	O
prevalence	O
of	O
a	O
malignant	O
degeneration	O
of	O
prostate	O
tissue	O
by	O
approximately	O
90%	O
.	O
</s>
<s>
Shown	O
below	O
is	O
an	O
MRI	B-Algorithm
brain	O
scan	O
(	O
in	O
the	O
axial	O
plane	O
,	O
that	O
is	O
slicing	O
from	O
front-to-back	O
and	O
side-to-side	O
through	O
the	O
head	O
)	O
showing	O
a	O
brain	O
tumor	O
(	O
meningioma	O
)	O
at	O
the	O
bottom	O
right	O
.	O
</s>
<s>
The	O
red	O
box	O
shows	O
the	O
volume	O
of	O
interest	O
from	O
which	O
chemical	O
information	O
was	O
obtained	O
by	O
MRS	O
(	O
a	O
cube	O
with	O
2cm	O
sides	O
which	O
produces	O
a	O
square	O
when	O
intersecting	O
the	O
5mm	O
thick	O
slice	O
of	O
the	O
MRI	B-Algorithm
scan	O
)	O
.	O
</s>
<s>
In	O
1H	O
Magnetic	B-Algorithm
Resonance	I-Algorithm
Spectroscopy	I-Algorithm
each	O
proton	B-Application
can	O
be	O
visualized	O
at	O
a	O
specific	O
chemical	O
shift	O
(	O
peak	O
position	O
along	O
x-axis	O
)	O
depending	O
on	O
its	O
chemical	O
environment	O
.	O
</s>
<s>
This	O
chemical	O
shift	O
is	O
dictated	O
by	O
neighboring	O
protons	B-Application
within	O
the	O
molecule	O
.	O
</s>
<s>
MRS	O
,	O
used	O
in	O
conjunction	O
with	O
MRI	B-Algorithm
or	O
some	O
other	O
imaging	O
technique	O
,	O
can	O
be	O
used	O
to	O
detect	O
changes	O
in	O
the	O
concentrations	O
of	O
these	O
metabolites	O
,	O
or	O
significantly	O
abnormal	O
concentrations	O
of	O
these	O
metabolites	O
.	O
</s>
<s>
In	O
addition	O
,	O
despite	O
recent	O
efforts	O
toward	O
international	O
expert	O
consensus	O
on	O
methodological	O
details	O
like	O
shimming	O
,	O
motion	O
correction	O
,	O
spectral	O
editing	O
,	O
spectroscopic	O
neuroimaging	O
,	O
other	O
advanced	O
acquisition	O
methods	O
,	O
data	O
processing	O
and	O
quantification	O
,	O
application	O
to	O
brain	O
,	O
proton	B-Application
spectroscopy	O
application	O
to	O
skeletal	O
muscle	O
,	O
phosphorus	O
application	O
to	O
skeletal	O
muscle	O
,	O
methods	O
description	O
,	O
results	O
reporting	O
,	O
and	O
other	O
considerations	O
,	O
currently	O
published	O
implementations	O
of	O
in	B-Algorithm
vivo	I-Algorithm
magnetic	I-Algorithm
resonance	I-Algorithm
spectroscopy	I-Algorithm
cluster	O
into	O
literatures	O
exhibiting	O
a	O
broad	O
variety	O
of	O
individualized	O
acquisition	O
,	O
processing	O
,	O
quantification	O
,	O
and	O
reporting	O
techniques	O
.	O
</s>
<s>
This	O
situation	O
may	O
contribute	O
to	O
a	O
low	O
sensitivity	O
and	O
specificity	O
of	O
,	O
for	O
example	O
,	O
in	O
vivo	O
proton	B-Application
magnetic	B-Algorithm
resonance	I-Algorithm
spectroscopy	I-Algorithm
to	O
disorders	O
such	O
as	O
multiple	O
sclerosis	O
,	O
that	O
continue	O
to	O
fall	O
below	O
clinically	O
beneficial	O
thresholds	O
for	O
,	O
e.g.	O
,	O
diagnosis	O
.	O
</s>
<s>
This	O
is	O
in	O
large	O
part	O
because	O
of	O
the	O
relatively	O
high	O
sensitivity	O
of	O
phosphorus	O
NMR	O
(	O
7%	O
of	O
protons	B-Application
)	O
combined	O
with	O
a	O
100%	O
natural	O
abundance	O
.	O
</s>
<s>
There	O
is	O
great	O
overlap	O
in	O
what	O
1H	O
MRS	O
and	O
13C	O
MRS	O
can	O
obtain	O
spectra-wise	O
and	O
large	O
reason	O
,	O
combined	O
with	O
1H	O
MRS	O
's	O
high	O
sensitivity	O
,	O
why	O
13C	O
MRS	O
has	O
never	O
seen	O
wide	O
application	O
like	O
1H	O
MRS	O
.	O
See	O
also	O
Hyperpolarized	B-Algorithm
carbon-13	I-Algorithm
MRI	I-Algorithm
.	O
</s>
<s>
Sodium	O
NMR	O
is	O
infamous	O
for	O
its	O
low	O
sensitivity	O
(	O
9.2	O
%	O
relative	O
to	O
proton	B-Application
sensitivity	O
)	O
and	O
low	O
SNR	O
because	O
of	O
its	O
low	O
sodium	O
concentration	O
(	O
30	O
-	O
100	O
mM	O
)	O
,	O
especially	O
compared	O
to	O
protons	B-Application
(	O
40	O
-	O
50	O
M	O
)	O
.	O
</s>
<s>
Fluorine	O
NMR	O
has	O
high	O
sensitivity	O
(	O
82%	O
relative	O
to	O
proton	B-Application
sensitivity	O
)	O
and	O
100%	O
natural	O
abundance	O
.	O
</s>
<s>
1H	O
MRI	B-Algorithm
provides	O
the	O
anatomical	O
landmarks	O
,	O
while	O
19F	O
MRI/MRS	O
allows	O
us	O
to	O
follow	O
and	O
map	O
the	O
specific	O
interactions	O
of	O
specific	O
compounds	O
.	O
</s>
