MRI 4D flow velocity is used to evaluate relative blood pressures in the aorta throughout the cardiac cycle. This (3D+t) pressure mapping is used to assess: 1) relationship between trans-aortic pressure gradient with age and aortic tapering (proximal to distal narrowing in lumen area), 2) effect of temporal resolution. We studied 47 healthy subjects (49±17.6 years, 24 men) who underwent 4D flow MRI, among them 20 were reconstructed in 20 and 50 phases per cardiac cycle. Pressure gradients maps were estimated from velocity fields using the Navier-Stokes equations. Relative pressures were calculated using an iterative algorithm while considering a zero pressure at the aortic valve. Distal (DA) to proximal (PA) aortic pressure gradient decreased with age (r=0.60, p