<s>
Magnetic	B-Algorithm
resonance	I-Algorithm
elastography	I-Algorithm
(	O
MRE	O
)	O
is	O
a	O
form	O
of	O
elastography	B-Algorithm
that	O
specifically	O
leverages	O
MRI	O
to	O
quantify	O
and	O
subsequently	O
map	O
the	O
mechanical	O
properties	O
(	O
elasticity	O
or	O
stiffness	B-Algorithm
)	O
of	O
soft	O
tissue	O
.	O
</s>
<s>
a	O
breast	O
tumor	O
)	O
is	O
often	O
stiffer	O
than	O
the	O
surrounding	O
normal	O
(	O
)	O
tissue	O
,	O
providing	O
motivation	O
to	O
assess	O
tissue	O
stiffness	B-Algorithm
.	O
</s>
<s>
Conventional	O
imaging	O
techniques	O
of	O
CT	O
,	O
MRI	O
,	O
US	B-Application
,	O
and	O
nuclear	O
medicine	O
are	O
unable	O
to	O
offer	O
any	O
insight	O
on	O
the	O
elastic	O
modulus	O
of	O
soft	O
tissue	O
.	O
</s>
<s>
MRE	O
,	O
as	O
a	O
quantitative	O
method	O
of	O
assessing	O
tissue	O
stiffness	B-Algorithm
,	O
provides	O
reliable	O
insight	O
to	O
visualize	O
a	O
variety	O
of	O
disease	O
processes	O
which	O
affect	O
tissue	O
stiffness	B-Algorithm
in	O
the	O
liver	O
,	O
brain	O
,	O
heart	O
,	O
pancreas	O
,	O
kidney	O
,	O
spleen	O
,	O
breast	O
,	O
uterus	O
,	O
prostate	O
,	O
and	O
skeletal	O
muscle	O
.	O
</s>
<s>
MRE	O
is	O
conducted	O
in	O
three	O
steps	O
:	O
first	O
,	O
a	O
mechanical	O
vibrator	O
is	O
used	O
on	O
the	O
surface	O
of	O
the	O
patient	O
's	O
body	O
to	O
generate	O
shear	O
waves	O
that	O
travel	O
into	O
the	O
patient	O
's	O
deeper	O
tissues	O
;	O
second	O
,	O
an	O
MRI	O
acquisition	O
sequence	O
measures	O
the	O
propagation	O
and	O
velocity	O
of	O
the	O
waves	O
;	O
and	O
finally	O
this	O
information	O
is	O
processed	O
by	O
an	O
inversion	O
algorithm	O
to	O
quantitatively	O
infer	O
and	O
map	O
tissue	O
stiffness	B-Algorithm
in	O
3-D	O
.	O
</s>
<s>
This	O
stiffness	B-Algorithm
map	O
is	O
called	O
an	O
elastogram	O
,	O
and	O
is	O
the	O
final	O
output	O
of	O
MRE	O
,	O
along	O
with	O
conventional	O
3-D	O
MRI	O
images	O
as	O
shown	O
on	O
the	O
right	O
.	O
</s>
<s>
MRE	O
quantitatively	O
determines	O
the	O
stiffness	B-Algorithm
of	O
biological	O
tissues	O
by	O
measuring	O
its	O
mechanical	O
response	O
to	O
an	O
external	O
stress	O
.	O
</s>
<s>
The	O
elastic	O
modulus	O
quantifies	O
the	O
stiffness	B-Algorithm
of	O
a	O
material	O
,	O
or	O
how	O
well	O
it	O
resists	O
elastic	O
deformation	O
as	O
a	O
force	O
is	O
applied	O
.	O
</s>
<s>
Yet	O
,	O
MRE	O
and	O
other	O
elastography	B-Algorithm
imaging	O
techniques	O
typically	O
utilize	O
a	O
mechanical	O
parameter	O
estimation	O
that	O
assumes	O
biological	O
tissues	O
to	O
be	O
linearly	O
elastic	O
and	O
isotropic	O
for	O
simplicity	O
purposes	O
.	O
</s>
<s>
This	O
relationship	O
can	O
be	O
used	O
to	O
estimate	O
the	O
stiffness	B-Algorithm
of	O
biological	O
tissues	O
based	O
on	O
the	O
calculated	O
shear	O
modulus	O
from	O
shear-wave	O
propagation	O
measurements	O
.	O
</s>
<s>
MRE-based	O
measurement	O
of	O
liver	O
stiffness	B-Algorithm
has	O
emerged	O
as	O
the	O
most	O
accurate	O
non-invasive	O
technique	O
for	O
detecting	O
and	O
staging	O
liver	O
fibrosis	O
.	O
</s>
<s>
MRE	O
provides	O
quantitative	O
maps	O
of	O
tissue	O
stiffness	B-Algorithm
over	O
large	O
regions	O
of	O
the	O
liver	O
.	O
</s>
<s>
Abnormally	O
increased	O
liver	O
stiffness	B-Algorithm
is	O
a	O
direct	O
consequence	O
of	O
liver	O
fibrosis	O
.	O
</s>
<s>
Patients	O
should	O
fast	O
for	O
3	O
to	O
4	O
hours	O
prior	O
to	O
their	O
MRE	O
exam	O
to	O
allow	O
for	O
the	O
most	O
accurate	O
measurement	O
of	O
liver	O
stiffness	B-Algorithm
.	O
</s>
<s>
A	O
recent	O
study	O
looked	O
into	O
both	O
the	O
isotropic	O
and	O
anisotropic	O
stiffness	B-Algorithm
in	O
brain	O
and	O
found	O
a	O
correlation	O
between	O
the	O
two	O
and	O
with	O
age	O
,	O
particularly	O
in	O
gray	O
matter	O
.	O
</s>
<s>
MRE	O
has	O
also	O
been	O
applied	O
to	O
functional	B-Algorithm
neuroimaging	I-Algorithm
.	O
</s>
<s>
Whereas	O
functional	B-Algorithm
magnetic	I-Algorithm
resonance	I-Algorithm
imaging	I-Algorithm
(	O
fMRI	B-Algorithm
)	O
infers	O
brain	O
activity	O
by	O
detecting	O
relatively	O
slow	O
changes	O
in	O
blood	O
flow	O
,	O
functional	O
MRE	O
is	O
capable	O
of	O
detecting	O
neuromechanical	O
changes	O
in	O
the	O
brain	O
related	O
to	O
neuronal	O
activity	O
occurring	O
on	O
the	O
100-millisecond	O
scale	O
.	O
</s>
<s>
Studies	O
investigating	O
renal	O
diseases	O
such	O
as	O
renal	O
allograft	O
dysfunction	O
,	O
lupus	O
nephritis	O
,	O
immunoglobulin	O
A	O
nephropathy	O
(	O
IgAN	O
)	O
,	O
diabetic	O
nephrology	O
,	O
renal	O
tumors	O
and	O
chronic	O
kidney	O
disease	O
demonstrate	O
that	O
kidney	O
stiffness	B-Algorithm
is	O
sensitive	O
to	O
kidney	O
function	O
and	O
renal	O
perfusion	O
.	O
</s>
<s>
Preliminary	O
results	O
in	O
patients	O
with	O
prostate	O
cancer	O
showed	O
that	O
changes	O
in	O
stiffness	B-Algorithm
allowed	O
differentiation	O
of	O
cancerous	O
tissue	O
from	O
normal	O
tissue	O
.	O
</s>
<s>
Magnetic	B-Algorithm
Resonance	I-Algorithm
Elastography	I-Algorithm
has	O
been	O
successfully	O
used	O
in	O
patients	O
with	O
prostate	O
cancer	O
showing	O
high	O
specificity	O
and	O
sensitivity	O
in	O
differentiating	O
prostate	O
cancer	O
from	O
benign	O
prostatic	O
diseases	O
(	O
see	O
figure	O
on	O
right	O
(	O
b	O
)	O
)	O
.	O
</s>
<s>
Even	O
higher	O
specificity	O
of	O
95%	O
for	O
prostate	O
cancer	O
was	O
achieved	O
when	O
Magnetic	B-Algorithm
Resonance	I-Algorithm
Elastography	I-Algorithm
was	O
combined	O
with	O
systematic	O
image	O
interpretation	O
using	O
PI-RADS	B-Algorithm
(	O
version	O
2.1	O
)	O
.	O
</s>
<s>
Given	O
that	O
pancreatic	O
diseases	O
including	O
pancreatitis	O
and	O
pancreatic	O
cancer	O
significantly	O
increase	O
stiffness	B-Algorithm
,	O
MRE	O
is	O
a	O
promising	O
tool	O
for	O
diagnosing	O
benign	O
and	O
malignant	O
conditions	O
of	O
the	O
pancreas	O
.	O
</s>
<s>
Abnormally	O
high	O
pancreatic	O
stiffness	B-Algorithm
was	O
detected	O
by	O
MRE	O
in	O
patients	O
with	O
both	O
acute	O
and	O
chronic	O
pancreatitis	O
.	O
</s>
<s>
Pancreatic	O
stiffness	B-Algorithm
was	O
also	O
used	O
to	O
distinguish	O
pancreatic	O
malignancy	O
from	O
benign	O
masses	O
and	O
to	O
predict	O
the	O
occurrence	O
of	O
pancreatic	O
fistula	O
after	O
pancreaticoenteric	O
anastomosis	O
.	O
</s>
<s>
Quantification	O
of	O
the	O
volume	O
of	O
pancreatic	O
tumors	O
based	O
on	O
tomoelastographic	O
measurement	O
of	O
stiffness	B-Algorithm
was	O
found	O
to	O
be	O
excellently	O
correlated	O
with	O
tumor	O
volumes	O
estimated	O
by	O
contrast-enhanced	B-Algorithm
computed	O
tomography	O
.	O
</s>
<s>
In	O
patients	O
with	O
pancreatic	O
ductal	O
adenocarcinoma	O
stiffness	B-Algorithm
was	O
found	O
to	O
be	O
elevated	O
in	O
the	O
tumor	O
as	O
well	O
as	O
in	O
pancreatic	O
parenchyma	O
distal	O
to	O
the	O
tumor	O
,	O
suggesting	O
heterogeneous	O
pancreatic	O
involvement	O
(	O
figure	O
on	O
right	O
(	O
c	O
)	O
)	O
.	O
</s>
