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Figure 4 Cross-sectional magnetic resonance angiography images of the right coronary artery (RCA) (arrows) before (left) and after (right) nitroglycerin (NTG), showing vasodilation in a healthy volunteer (RCA area increased from 12.0 to 17.0 mm²) (top) and a heart transplant patient (RCA area increased from 12.6 to 15.5 mm²) (bottom). Note the multiple similarities in the shape/features of the adjacent atrioventricular groove, right atrium and ventricle, and chest wall on the pre- and post-NTG images, indicating good spatial correspondence.