Biomedical Engineering Reference
In-Depth Information
between the two groups. Carotid branch vessels were well visualized from the
aortic arch to the intracerebral circulation. The average venous contamination
score was 0.56. Breath-holding greatly improves the sharpness of the aortic arch
and great vessel origins but has no effect on visualization of the carotid vessels.
High-resolution breath-hold contrast-enhanced MRA can produce high-quality,
artifact-free images of the entire carotid circulation from the aortic arch to the
intracerebral circulation.
3.4.9 K-space 3D Navigator-Gated MRA
To acquire the center of k-space while extending three-dimensional free-
breathing navigator-gated coronary MRA by an initial single breath-hold [9], this
approach was successfully applied. Resulting images were compared with con-
ventionally acquired free-breathing navigator-gated MR angiograms. The acqui-
sition of k-space center during the single breath-hold resulted in an appreciable
increase in the signal-to-noise ratio. Visible length of the right coronary artery, as
well as contrast-to-noise ratio between blood and the myocardial muscle were
identical. The breath-hold extension was shown to be a valuable technique that
may be combined with first-pass contrast-enhanced MR imaging. The other ad-
vantage was the creation of photographic freeze scans of coronary small arteries
and heart within each heartbeat of approximately 80 msec intervals.
3.4.10 MR Arterial Spin Tagging Projection Coronary
MRA Technique
Conventional coronary MRA techniques display the coronary blood-pool along
with the surrounding structures, including myocardium, the ventricular and
atrial blood-pool, and the great vessels [10]. This representation of the coronary
lumen is not directly analogous to the information provided by X-ray coronary
angiography, in which the coronary lumen displayed by iodinated contrast agent
is seen. Analogous “luminographic” data may be obtained using MR arterial spin
tagging (projection coronary MRA) techniques. Such an approach was imple-
mented using a 2D selective “pencil” excitation for aortic spin tagging in concert
with a 3D interleaved segmented spiral imaging sequence with free-breathing
and real-time navigator technology. This technique allows for selective 3D
