Measurement of in vivo strain and stiffness-based parameters. (A) Strain is quantified by measuring aortic cross-sectional area at peak systole (A_s) and diastole (A_d) at the level of the mid-ascending thoracic aorta using 2D phase contrast MRI. (B) Blood pressure is measured using sphygmomanometery to characterize loading on the aortic wall at peak systole (P_s) and diastole (P_d) which is used in the calculation of stiffness-based parameters.