Anterior most artery in lateral view of aortic arch angiogram

Which is the anterior most artery in lateral view of aortic arch angiogram?

Internal mammary arteries are the most anterior arteries visualized in the lateral view after injection of contrast into the aortic arch. They can be seen within the sternal contour as a pulsatile darkening of the posterior rim of the sternum in the lateral view.

Internal mammary arteries are important conduits for coronary bypass grafting. They are usually visualized either by directly injecting contrast into their opening from the subclavian or by non selective injection in the corresponding subclavian artery.