Quantitative 4D flow MRI-derived thoracic aortic normal values of 2D flow MRI parameters in healthy volunteers

Purpose To utilize 4 D flow MRI to acquire normal values of "conventional 2 D flow MRI parameters" in healthy volunteers in order to replace multiple single 2 D flow measurements with a single 4 D flow acquisition.Materials and Methods A kt-GRAPPA accelerated 4 D flow sequence was used. Flow volumes were assessed by forward (FFV), backward (BFV), and net flow volumes (NFV) [ml/heart-beat] and flow velocities by axial (VAX) and absolute velocity (VABS) [m/s] in 116 volunteers (58 females, 43 +/- 13 years). The aortic regurgitant fraction (RF) was calculated.Results The sex-neutral mean FFV, BFV, NFV, and RF in the ascending aorta were 93.5 +/- 14.8, 3.6 +/- 2.8, 89.9 +/- 0.6 ml/ heartbeat, and 3.9 +/- 2.9 %, respectively. Significantly higher values were seen in males regarding FFV, BFV, NFV and RF, but there was no sex dependency regarding VAX and VABS. The mean maximum VAX was lower (1.01 +/- 0.31 m/s) than VABS (1.23 +/- 0.35 m/s). We were able to determine normal ranges for all intended parameters.Conclusion This study provides quantitative 4 D flow-derived thoracic aortic normal values of 2 D flow parameters in heal-thy volunteers. FFV, BFV, NFV, and VAX did not differ significantly from single 2 D flow acquisitions and could therefore replace time-consuming multiple single 2 D flow acquisitions. VABS should not be used interchangeably. Key points: 4 D flow MRI can be used to replace 2 D flow MRI measurements. The parameter absolute velocities can be assessed by 4 D flow MRI. There are sex-dependent differences regarding forward, backward, net aortic blood flow and the aortic valve regurgit ant fraction.