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Purpose To test the feasibility and effectiveness of using maximum intensity plots (MIPs) based on 4D flow MRI velocity data to assess systolic peak velocities in a cohort of bicuspid aortic valve (BAV) patients. Materials and Methods 4D flow MRI at 1.5 T was performed on 51 BAV patients. MIPs were generated from the 4D flow MRI velocity data and used by 2 users to determine peak velocities in 3 regions of interest (ROI): ascending aorta (AAo), aortic arch and descending aorta. 4D flow MRI peak velocities in the AAo were compared to peak velocities recorded by 2D phase contrast MRI (2D PCMRI) in a subcohort of 36 patients and by Doppler echocardiography in a subcohort of 34 patients. 4D flow MRI peak velocities recorded by each observer were compared for all ROIs to test for inter-observer variability. Results 4D flow MRI recorded significantly higher velocities compared to 2D PCMRI (2.04 ± 0.71 m/s vs 1.69 ± 0.79 m/s, 17.2% difference, p < 0.001) and similar velocities compared to Doppler echocardiography. There was excellent agreement between the observers with a mean difference of 0.005 m/s and an intraclass correlation coefficient of 0.98. Conclusion 4D flow MRI velocity MIPs allow for efficient measurement of peak velocities in BAV patients with higher accuracy than 2D PCMRI and similar accuracy to Doppler echocardiography.

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