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Proximal aortic function estimated by Magnetic Resonance Imaging (MRI) is booming to assess aortic diseases as stiffness indices have been shown to be independent predictors of cardiovascular events and mortality.Calculation of aortic distensibility (AD) requires MRI aortic strain data, but also local blood pressure (BP). Because of magnetic field limitations, most MRI studies used Brachial Pulse Pressure (bPP) as a surrogate of Central Pulse Pressure (cPP).New devices allow the estimation of cPP from brachial cuff and are compatible with MRI. Our aim was to evaluate differences in AD assessed using cPP and bPP.Brachial and central BP were recorded using a 6 meters hose and the SphygmoCor Xcel device (AtCor Medical, Australia) in 58 volunteers (31 males) during non contrast MRI SSFP acquisition of orthogonal section of the ascending aorta (AA). Cross sectional lumen areas were determined using a fully automated contouring method (ARTFUN software). AD of the AA was defined as (Area_max-Area_min)/(Area_min x PP) with PP = bPP and cPP for AD_b and AD_c respectively.Among the 58 patients, 18(31%) were treated for hypertension, 6(10%) were active smokers, none were diabetic or dyslipidaemic. Median age was 43 years(28–67).AD_c and AD_b were highly correlated (r = 0.986, p < 0.001) with a significant bias across the range leading to underestimation of AD_b (−1.87 ± 1.6610–3 mmHg) for higher AD values (r = −0.94, p < 0.0001, figure 1).The correlation with age was stronger using AD_c (ρ = −0.87; p < 0,001) than AD_b (ρ = −0.83, p < 0.001). AD difference between the 2-age quantiles was higher when using AD_c (−7.08 ± 0.56; p < 0,001) compared to AD_b (−4.26 ± 0.38, p < 0.001, figure 2). Only in young subjects, AD_c was significantly higher than AD_b (p < 0,0001).Using cPP instead of bPP leads to differences in MRI assessment of AD especially in younger subjects. bPP might not be suitable as a surrogate measure of ascending aortic PP for AD assessment. The use of cPP improves aortic stiffness MRI assessment and may be useful to detect early aortic function impairment in young patients.