Improved quantification of coronary artery luminal stenosis in the presence of heavy calcifications using photon-counting detector CT

Coronary CT Angiography (cCTA) is commonly used to detect and quantify luminal stenoses in patients with coronary artery disease (CAD). However, its use is limited in patients with heavy coronary calcifications due to calcium blooming, which is caused by insufficient spatial resolution. This study evaluated the ability of a photon-counting-detector (PCD) CT in quantifying luminal stenosis in the presence of heavy calcifications relative to an energy-integrating-detector (EID) CT. Cylindrical rods of 4.5 mm diameter (with 3 mm lumen), which contained calcium hydroxyapatite (CaHA) to emulate calcifications of varying shapes and sizes and an iodine or blood analog to emulate the coronary lumen, were placed within an anthropomorphic thorax phantom and scanned at matched dose on an EID-CT and a PCD-CT scanner. Stenoses were qualitatively evaluated and quantified using commercial software. Measured percent area stenosis was compared to reference values. PCD-CT provided better visualization of calcium plaques and the patent lumen, and more accurate stenosis quantification for all plaques. In one rod (75% occlusion with ring-shaped plaque), only PCD-CT was able to determine that the vessel was not fully obstructed. The phantom results indicate luminal stenoses that were previously considered non-assessable due to the presence of heavily-calcified plaques can be assessed using PCD-CT. Clinical studies to support these conclusions are underway.