Chapter 12. Computed Tomography of the Coronary Arteries
Interpretation of the in-stent coronary lumen by computed tomography angiography is improved by which of the following?
B. High metal strut density
D. Absence of drug coating
The size of the artifacts depends on the strut size and the quality of the scanner and is fairly constant regardless of the stent diameter. Therefore, the proportion of artifact-free, interpretable, lumen increases disproportionally with increased vessel size. High heart rates and denser metal create more artifacts, whereas nonmetal drug coatings have no effect.
In case of moderate coronary stenosis on computed tomography (CT), hemodynamic significance is thought to be:
Moderate stenosis means a 50% to 70% lumen narrowing, which may or may not cause hemodynamic obstruction.
Which statement about plaque characterization by CT is true?
A. Fibrous plaques are expected to have lower attenuation values than lipid-rich plaques.
B. Metabolic activity on CT angiography predicts plaque rupture.
C. The border between vessel lumen and plaque is more difficult to delineate than the outer plaque border.
D. Contrast medium affects the measured attenuation values in the plaque.
Due to image filtering, motion, and perhaps microvascular enhancement, the attenuation values measured in plaques increase when the adjacent lumen contains more contrast. If anything, fat should result in lower attenuation values than soft tissues. Metabolic activity cannot be assessed by CT angiography. Due to the vasa vasorum and small attenuation differences with the epicardial tissue, the delineation of the outer plaque borders is more difficult.
Which statement regarding CT angiography (CTA)–derived fractional flow reserve is true?
A. It requires dedicated CT equipment.
B. It requires administration of an intravenous vasodilator.
C. It requires detailed segmentation of the coronary arteries.
D. It requires purchase of a supercomputer.