(3D
MRA) The 3D
angiography technique can be applied to focus on fast flowing (arterial) blood and to visualize small tortuous vessels. 3D
TOF images are less sensitive to turbulent
flow artifacts.
The advantage of this approach is that the signal, acquired from the entire
volume has an increased
signal to noise ratio. Slices are defined by a
second phase encoded axis, which divides the volume into 'partitions'.
3D
TOF MRA is acquired with
3D FT slabs or multiple overlapping thin
3D FT slabs (
MOTSA) depending on the coverage required and the range of flow-velocities under examination.
Such 3D techniques can provide equal
spatial resolution along all three axes, i.e. be '
isotropic', or the partition thickness can be greater or less than the in plane
spatial resolution in which case can be said to be 'an
isotropic'.
The
circle of Willis, anatomy as well as its fast arterial
flow, lends itself well to both 3D
TOF and 2D or 3D
phase contrast angiography.