128-Slice dual source coronary CTA: defining optimal arterial enhancement levels

This study aims to correlate coronary artery enhancement levels with quality of vessel visualization and calcified plaque visualization using a 128-slice dual-source CT (DSCT) scanner. Coronary CT angiography exams from 52 patients, mean age of 55 years (range, 22–90) and mean weight of 184 lbs (range, 120–320 lbs), were reviewed retrospectively. Contrast infusion rates ranged from 4.5 to 7 mL/s (mean, 5.8 mL/s). Postcontrast density of the largest calcified plaque and postcontrast density of the left main (LM) and right coronary arteries (RCA) were recorded. Enhancement quality was graded as 1 = suboptimal, 2 = adequate for diagnosis, and 3 = excellent. Pre- and postcontrast acquisitions were compared for calcified plaque conspicuity. The largest calcified plaque density was a mean of 862 HU (range, 376 to 1,384 HU) on the postcontrast scan. The mean LM and RCA coronary artery enhancement levels for studies of excellent enhancement quality (N = 43) were 468 and 457 HU, respectively, higher than mean enhancement levels of 320 and 322 HU for adequate enhancement quality (N = 8) (p < 0.0001 and 0.009). One study was graded as a nondiagnostic enhancement quality. Twenty-five subjects had calcified plaque, 3/8 with adequate and 22/43 with excellent enhancement quality. At least one calcified plaque measuring <2 mm was isodense to contrast enhancement on axial images in 5/25; all five were in the highest enhancement quality group. High coronary artery enhancement quality using 128-DSCT is associated with mean proximal coronary artery enhancement levels over 400 HU. High levels of enhancement may obscure small, calcified plaques.