Biomedical Engineering Reference
In-Depth Information
proton magnetic resonance spectroscopic imaging (MRSI) estimated individual
tissue contributions to the spectroscopic voxels in multiple sclerosis (MS).
3.4.25 Coronary MRA
For assessment of patients with atherosclerotic CAD, CMRA is reported use-
ful for detection of patency of bypass grafts. Patients with suspected coronary
artery anomalies and patients with Kawasaki disease and coronary aneurysms
are among those for whom CMRA has demonstrated clinical usefulness. At cen-
ters with appropriate expertise and resources, CMRA also appears to be of value
for exclusion of severe proximal multivessel CAD in selected patients. Data from
multicenter trials defined the clinical role of CMRA, particularly as it relates to
assessment of CAD. Future developments and enhancements of CMRA promise
better lumen and coronary artery wall imaging. This may become the new target
in noninvasive evaluation of CAD [25].
3.4.26 4D Phase Contrast (PC) Technique
4D PC technique was demonstrated for its feasibility that permits spatial and
temporal coverage of an entire 3D volume [26]. It validated quantitatively the
accuracy against an established time resolved 2D PC technique to explore advan-
tages of the approach with regard to the 4D nature of the data. Time-resolved,
3D anatomical images were generated simultaneously with registered three-
directional velocity vector fields. Improvements were compared to prior meth-
ods for gated and respiratory compensated image acquisition, interleaved flow
encoding with freely selectable velocity encoding (VENC) along each spatial di-
rection, and flexible trade-off between temporal resolution and total acquisition
time. The implementation was validated against established 2D PC techniques
using a well-defined phantom, and successfully applied in volunteer and patient
examinations. Human studies were performed after contrast administration in
order to compensate for loss of in-flow enhancement in the 4D approach. Advan-
tages of the 4D approach included the complete spatial and temporal coverage
of the cardiovascular region of interest and the ability to obtain high spatial
resolution in all three dimensions with higher signal-to-noise ratio compared
to 2D methods at the same resolution. In addition, the 4D nature of the data
offered a variety of image processing options, such as magnitude and velocity
