Calcium evaluation using coronary computed tomography in combination with optical coherence tomography

Optical coherence tomography (OCT) can assess calcium thickness, a key factor for predicting good stent expansion; however, it underestimates coronary calcium severity due to its penetration limitation. This study aimed to evaluate computed tomography (CT) and OCT images to assess calcification. We investigated 25 left anterior descending arteries of 25 patients, using coronary CT and OCT, and assessed their calcification. Of the 25 vessels, 1811 pairs of CT and OCT cross-sectional images were co-registered. Of the 1811 cross-sectional CT images, calcification was not detectable in 256 (14.1%) of the corresponding OCT images due to limited penetration. In the 1555 OCT calcium-detectable images, the maximum calcium thickness was not detectable in 763 (49.1%) images compared to the CT images. In CT images of slices corresponding to undetected calcium in OCT images, the angle, thickness, and maximum density of calcium were significantly smaller compared to slices corresponding to detected calcium in OCT. Calcium with an undetectable maximum thickness in the corresponding OCT image had a significantly greater calcium angle, thickness, and density than calcium with a detectable maximum thickness. There was an excellent correlation between CT and OCT with respect to calcium angle ( R= 0.82, P < 0.001). The calcium thickness on the OCT image had a stronger correlation with the maximum density on the corresponding CT image (R = 0.73, P < 0.001) than with the calcium thickness on the CT image (R = 0.61, P < 0.001). Cross-sectional CT imaging allows for pre-procedural assessment of calcium morphology and severity and could complement the lack of information on calcium severity in OCT-guided percutaneous coronary intervention.