Assessment of isotropic calcium using 0.5-mm reconstructions from 320-row CT data sets identifies more patients with non-zero Agatston score and more subclinical atherosclerosis than standard 3.0-mm coronary artery calcium scan and CT angiography

Background: The presence of calcified plaque in coronary arteries can be quantified by using 0.5-mm isotropic reconstructions from 320-row CT without increased radiation dose. Little is known about reclassification of patients with non-zero Agatston scores and quantitative measures of calcified plaque using 0.5-mm reconstructions. Objective: The aim was to compare proportions of zero vs non-zero Agatston scores (subclinical atherosclerosis) in 0.5-mm isotropic reconstructions vs standard 3.0-mm and CT angiography (CTA) scans on 320-row CT. Methods: Prospectively, we quantified calcified plaque in coronary arteries in 104 patients by using non-contrast-enhanced scans with 0.5 and 3.0mm. Coronary calcium assessment was determined by 2 observers. Clinically indicated CTA was also performed; coronary calcium assessment findings were compared with CTA. Ranked Wilcoxon test and χ² test were performed for comparison. Reproducibility for proportion of zero vs non-zero was assessed by κ statistics. Results: Median Agatston score (41.9 [interquartile range (IQR), 3.7-213.6] vs 5.2 [IQR, 0.0-128.5]), calcium volume (53.6 mm³ [IQR, 8.1-202.3] vs 5.1 mm³ [IQR, 0.0-96.8],), and lesion number (10.0 [IQR, 3.5-18.5] vs 1.0 [IQR, 0.0-6.0]) were significantly higher on 0.5-mm reconstruction (P < .0001) than on 3.0-mm reconstruction. More patients with subclinical atherosclerosis were detected on 0.5mm than on 3.0mm and CTA scans (76.9% vs 53.8% vs 54.8%; P < .0001). The κ values for inter-rater agreement were 0.94 and 0.52 on 3.0- and 0.5-mm data sets, respectively. However, when Agatston scores < 10 were excluded from analysis, the κ value rose to 0.83. Conclusion: Isotropic 0.5-mm reconstruction detected 23.1% and 22.1% more patients with subclinical atherosclerosis than standard 3.0-mm scans and CTA, which may be more sensitive for the detection of subclinical atherosclerosis; its potential clinical utility needs to be validated in large, prospective studies.