<s>
Contrast	B-Algorithm
resolution	I-Algorithm
is	O
the	O
ability	O
to	O
distinguish	O
between	O
differences	O
in	O
intensity	O
in	O
an	O
image	O
.	O
</s>
<s>
The	O
measure	O
is	O
used	O
in	O
medical	B-Application
imaging	I-Application
to	O
quantify	O
the	O
quality	O
of	O
acquired	O
images	O
.	O
</s>
<s>
In	O
MRI	B-Algorithm
,	O
determining	O
contrast	O
is	O
of	O
high	O
importance	O
for	O
calibration	O
because	O
the	O
operator	O
has	O
a	O
high	O
degree	O
of	O
control	O
of	O
how	O
the	O
signal	O
intensities	O
of	O
various	O
structures	O
vary	O
in	O
the	O
images	O
by	O
using	O
different	O
MRI	B-Algorithm
methods	O
and	O
imaging	O
parameters	O
.	O
</s>
<s>
Unlike	O
most	O
other	O
imaging	O
modalities	O
,	O
such	O
as	O
x-ray	O
CT	O
in	O
which	O
the	O
Hounsfield	O
units	O
value	O
for	O
water	O
is	O
set	O
to	O
zero	O
,	O
there	O
is	O
no	O
standard	O
reference	O
signal	O
for	O
MRI	B-Algorithm
.	O
</s>
<s>
Thus	O
the	O
contrast-to-noise	B-Algorithm
ratio	I-Algorithm
is	O
often	O
employed	O
as	O
an	O
index	O
for	O
contrast	O
because	O
this	O
metric	O
does	O
not	O
require	O
a	O
reference	O
signal	O
.	O
</s>
<s>
Contrast	B-Algorithm
resolution	I-Algorithm
or	O
contrast-detail	O
is	O
an	O
approach	O
to	O
describing	O
the	O
image	O
quality	O
in	O
terms	O
of	O
both	O
the	O
image	O
contrast	O
and	O
resolution	O
.	O
</s>
<s>
Contrast	B-Algorithm
resolution	I-Algorithm
is	O
usually	O
measured	O
by	O
generating	O
a	O
pattern	O
from	O
a	O
test	O
object	O
that	O
depicts	O
how	O
image	O
contrast	O
changes	O
as	O
the	O
structures	O
being	O
imaged	O
get	O
smaller	O
and	O
closer	O
together	O
.	O
</s>
<s>
The	O
picture	O
below	O
shows	O
one	O
such	O
set	O
of	O
images	O
produced	O
using	O
the	O
low	O
contrast	O
detectability	O
inserts	O
of	O
the	O
phantom	O
employed	O
in	O
the	O
MRI	B-Algorithm
accreditation	O
program	O
of	O
the	O
American	O
College	O
of	O
Radiology	O
.	O
</s>
