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.