Volumetric Coronary Endothelial Function Assessment: a Feasibility Study Exploiting Stack‐of‐stars 3D Cine MRI and Image‐based Respiratory Self‐gating

Abnormal coronary endothelial function (CEF), manifesting as depressed vasoreactive responses to endothelial‐specific stressors, occurs early in atherosclerosis, independently predicts cardiovascular events, and responds to cardioprotective interventions. CEF is spatially heterogeneous along a coronary artery in patients with atherosclerosis, and thus recently developed and tested non‐invasive 2D MRI techniques to measure CEF may not capture the extent of changes in CEF in a given coronary artery. The purpose of this study was to develop and test the first volumetric coronary 3D MRI cine method for assessing CEF along the proximal and mid‐coronary arteries with isotropic spatial resolution and in free‐breathing. This approach, called 3D‐Stars, combines a 6 min continuous, untriggered golden‐angle stack‐of‐stars acquisition with a novel image‐based respiratory self‐gating method and cardiac and respiratory motion‐resolved reconstruction. The proposed respiratory self‐gating method agreed well with respiratory bellows and center‐of‐k‐space methods. In healthy subjects, 3D‐Stars vessel sharpness was non‐significantly different from that by conventional 2D radial in proximal segments, albeit lower in mid‐portions. Importantly, 3D‐Stars detected normal vasodilatation of the right coronary artery in response to endothelial‐dependent isometric handgrip stress in healthy subjects. Coronary artery cross‐sectional areas measured using 3D‐Stars were similar to those from 2D radial MRI when similar thresholding was used. In conclusion, 3D‐Stars offers good image quality and shows feasibility for non‐invasively studying vasoreactivity‐related lumen area changes along the proximal coronary artery in 3D during free‐breathing.