Brilliance workstation

CT image evaluation was performed on a separate 3D workstation (Brilliance workstation, Philips Medical Systems, Eindhoven, the Netherlands) by two experienced reviewers. CS was measured using the automatic calcium detection algorithm of the workstation, according to Agatston method, with a calcium threshold of 130 HU. CTA were analysed by assessment of axial slices, multiplanar reformations (along the vessel axis and cross-sectional images), and the three thin-slab maximum intensity projections. The coronary artery tree was divided into proximal, medial and distal, according to classic angiographic definition. Plaques were classified as obstructive or non-obstructive using a 50% threshold of luminal narrowing. The presence of obstructive coronary artery disease (CAD: > 50% lumen narrowing) in one vessel (single-vessel disease) or in two or three vessels (multivessel disease) was evaluated. Plaques were defined as structures >1mm² within and/or adjacent to the vessel lumen, distinct from lumen and surrounding tissue. Plaques were classified as: calcified – if they had more than 50% calcified tissue (density >130HU in native scans), mixed – if composed with <50% calcium, and non-calcified lesions - without any calcium. After independent evaluations, the final diagnosis was obtained by a consensus interpretation of the two reviewers.

All scans were analyzed independently by two experienced radiologists blinded to the clinical information, on a Brilliance workstation (Philips Healthcare, Amsterdam, Netherlands). Each lesion was identified using the multiplanar reconstruction technique and free mode maximum intensity projection.
The 15 coronary segments were defined according to American Heart Association (AHA) standards. Lesions were classified by the maximal luminal stenosis observed on any plane; grading of stenosis was further classified as normal appearing (<25%) and mild (25%–49%) and moderate (50%–74%) and severe (≥75%) narrowing. Plaques occupied by calcified tissue >50% of the plaque area (density > 130 Hounsfield units in native scans) were classified as calcified arterial plaques (CAP); those with <50% calcium were considered mixed calcified arterial plaques (MCAP); and plaques without calcium were classified as noncalcified arterial plaques (NCAP) as previously described (Figure 1).