Cardiac magnetic resonance image annotated to illustrate the 9 levels at which the aortic diameter was measured. 1. Aortic annulus; 2. Sinus of Valsalva; 3. Sinotubular junction; 4. Proximal ascending aorta; 5. Mid-ascending aorta; 6. Distal ascending aorta; 7. Proximal to the innominate trunk (proximal aortic arch); 8. Distal to the left subclavian artery (distal aortic arch); 9. Descending aorta at the level of the diaphragm.