<s>
Phase	B-Algorithm
contrast	I-Algorithm
magnetic	I-Algorithm
resonance	I-Algorithm
imaging	I-Algorithm
(	O
PC-MRI	O
)	O
is	O
a	O
specific	O
type	O
of	O
magnetic	O
resonance	O
imaging	O
used	O
primarily	O
to	O
determine	O
flow	O
velocities	O
.	O
</s>
<s>
It	O
also	O
provides	O
a	O
method	O
of	O
magnetic	B-Algorithm
resonance	I-Algorithm
angiography	I-Algorithm
.	O
</s>
<s>
Atoms	O
with	O
an	O
odd	O
number	O
of	O
protons	B-Application
or	O
neutrons	B-Device
have	O
a	O
randomly	O
aligned	O
angular	O
spin	O
momentum	O
.	O
</s>
<s>
These	O
spins	O
can	O
then	O
be	O
observed	O
by	O
receiver	O
coils	O
(	O
Radiofrequency	B-Algorithm
coils	I-Algorithm
)	O
using	O
Faraday	O
's	O
law	O
of	O
induction	O
.	O
</s>
<s>
All	O
of	O
these	O
spins	O
have	O
a	O
phase	O
that	O
is	O
dependent	O
on	O
the	O
atom	B-Language
's	O
velocity	O
.	O
</s>
<s>
A	O
choice	O
of	O
below	O
the	O
maximum	O
velocity	O
in	O
the	O
slice	O
will	O
induce	O
aliasing	B-Error_Name
in	O
the	O
image	O
where	O
a	O
velocity	O
just	O
greater	O
than	O
will	O
be	O
incorrectly	O
calculated	O
as	O
moving	O
in	O
the	O
opposite	O
direction	O
.	O
</s>
<s>
where	O
is	O
the	O
signal-to-noise	O
ratio	O
of	O
the	O
image	O
(	O
which	O
depends	O
on	O
the	O
magnetic	O
field	O
of	O
the	O
scanner	O
,	O
the	O
voxel	B-Algorithm
volume	O
,	O
and	O
the	O
acquisition	O
time	O
of	O
the	O
scan	O
)	O
.	O
</s>
<s>
For	O
medical	B-Application
imaging	I-Application
,	O
in	O
order	O
to	O
get	O
highly	O
resolved	O
scans	O
in	O
3D	O
space	O
and	O
time	O
without	O
motion	O
artifacts	O
from	O
the	O
heart	O
or	O
lungs	O
,	O
retrospective	O
cardiac	O
gating	O
and	O
respiratory	O
compensation	O
are	O
employed	O
.	O
</s>
<s>
Beginning	O
with	O
cardiac	O
gating	O
,	O
the	O
patient	O
's	O
ECG	B-Application
signal	O
is	O
recorded	O
throughout	O
the	O
imaging	O
process	O
.	O
</s>
<s>
After	O
the	O
scan	O
,	O
the	O
continuously	O
collected	O
data	O
in	O
k-space	B-Algorithm
(	O
temporary	O
image	O
space	O
)	O
can	O
be	O
assigned	O
accordingly	O
to	O
match-up	O
with	O
the	O
timing	O
of	O
the	O
heart	O
beat	O
and	O
lung	O
motion	O
of	O
the	O
patient	O
.	O
</s>
<s>
Phase	O
contrast	O
MRI	O
is	O
one	O
of	O
the	O
main	O
techniques	O
for	O
magnetic	B-Algorithm
resonance	I-Algorithm
angiography	I-Algorithm
(	O
MRA	O
)	O
.	O
</s>
<s>
Partial	B-Algorithm
volume	I-Algorithm
effects	I-Algorithm
(	O
when	O
a	O
voxel	B-Algorithm
contains	O
the	O
boundary	O
between	O
static	O
and	O
moving	O
materials	O
)	O
can	O
overestimate	O
phase	O
leading	O
to	O
inaccurate	O
velocities	O
at	O
the	O
interface	O
between	O
materials	O
or	O
tissues	O
.	O
</s>
<s>
A	O
Vastly	B-Algorithm
undersampled	I-Algorithm
Isotropic	I-Algorithm
Projection	I-Algorithm
Reconstruction	I-Algorithm
(	O
VIPR	O
)	O
is	O
a	O
radially	O
acquired	O
MRI	B-Algorithm
sequence	I-Algorithm
which	O
results	O
in	O
high-resolution	O
MRA	O
with	O
significantly	O
reduced	O
scan	O
times	O
,	O
and	O
without	O
the	O
need	O
for	O
breath-holding	O
.	O
</s>
