Biomedical Engineering Reference
In-Depth Information
visualization of the coronary lumen blood-pool, while signal from the surround-
ing structures is suppressed. However, there are technical hurdles for visualizing
the coronal arteries because of small size and near-constant mobility, which is
related to cardiac cycle and normal breathing.
3.4.11 Collateral Flow Assessment with Contrast
Enhanced MR Velocity Mapping
To correlate quantification of collateral flow in aortic coarctation with the mor-
phological visualization of the collateral vessels and to compare different ap-
proaches to the measurement of collateral flow [11], coarctation was examined
with T1-weighted spin-echo (T1-W SE) imaging and 3D contrast-enhanced MRA.
MR velocity mapping was performed at four levels in the descending aorta. The
flow immediately above and below the coarctation did not differ significantly.
Measuring within the coarctation resulted in flow overestimation. The increase
in flow from proximal to distal aorta was 12
±
21% in patients with no or uncer-
tain collaterals and 69
±
55% in patients with pronounced collaterals. Spin-echo
images and MRA were comparable in visualizing collateral vessels. The visual
estimation of collaterals was correlated reasonably well with flow quantification
MR velocity mapping. Collateral flow assessment with MR velocity mapping was
an accurate technique for evaluating the hemodynamic importance of a coarcta-
tion and was recommended if abundant collaterals are not visualized with spin
echo or MRA.
3.4.12 (Gd)-Enhanced Three-Dimensional Magnetic
Resonance Angiography
The goal of this technique was to evaluate the diagnostic value of gadolinium
(Gd)-enhanced three-dimensional MRA in patients with congenital and acquired
anomalies of the pulmonary and systemic veins [12]. Gadolinium-enhanced 3D
MRA is a fast magnetic resonance imaging technique that has shown great
promise in the evaluation of large and medium-sized arteries. However, its
application to venous anomalies has not been established. Gd-enhanced 3D
MRA examination was used for diagnosis with anomalies of the pulmonary or
