Biomedical Engineering Reference
In-Depth Information
application of a gadolinium (Gd)-based intravascular contrast agent provided an
additional source of signal and contrast by reducing T1(blood) and supporting
the visualization of more distal or branching segments of the coronary arterial
tree. For imaging, an optimized free breathing, navigator-gated and -corrected
3D inversion recovery (IR) sequence was used. For comparison, state-of-the-art
baseline 3D coronary MRA with T(2) preparation for non-exogenous contrast
enhancement was acquired. The combination of IR 3D coronary MRA, sophisti-
cated navigator technology, and B-22956 contrast agent allowed for an extensive
visualization of the LCA system. Postcontrast showed a significant increase in
both the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). Vessel
sharpness of the left anterior descending (LAD) artery and the left coronary
circumflex (LCx) were improved [34].
3.5 Limitations and Future Prospects
No specific MRA techniques have emerged so far that can provide sufficient sen-
sitivity and specificity for quantification. MR angiography still remains a clinical
choice of cardiovascular MR despite of cardiac and respiratory motion factors.
Physical principles further highlight the intricacies and need of MRA technical
improvements and modifications in coming years. From all techniques available,
2D/3D breath-hold coronary MRA(CMRA), black-blood FSE method, real-time
navigator for respiratory gating with slice position correction and contrast en-
hanced CMRA have been evaluated clinically useful for coronary wall imaging.
However, these high contrast angiography techniques suffer from limitations in
temporal and spatial resolution and motion artifacts. These restrictions further
limit its prediction value. Other hand, high contrast MR angiography techniques
suffer from limitations in temporal and spatial resolution and motion artifacts.
These advanced techniques have been described less sensitive
<
70% and speci-
ficity
<
75% while human artery risk in the wall is established
>
50% stenosis.
These methods no doubt provide a quick way to image blood flow in a long
segment of the artery for rapid burden measurements.
Other emerging MR techniques, such as water diffusion weighting, magneti-
zation transfer weighting, steady-state free precession (SSFP) sequences, con-
trast enhancement methods may provide thin slices. Still measurements and
plaque characterization methods are in infancy using thin slices. Some notable
