Quantification of aortic compliance in mice using radial phase contrast MRI

Purpose: To investigate the feasibility of radial phase contrast MR imaging to measure in vivo pulse wave velocity (PWV) and wall shear stress (WSS) in small animals on a 7 Tesla scanner. Materials and Methods: The aortic compliance of 9-month-old ApoE deficient (ApoE-KO) mice (n = 10) on a normal diet was studied in comparison to that of wild-type (WT) mice (n = 10). An undersampled, asymmetric echo radial phase contrast MR technique was developed to measure through plane blood flow velocity at axial slices along the descending aorta. The PWV and the time averaged WSS was calculated from the spatiotemporal flow data. The reproducibility of PWV and WSS was evaluated by taking multiple measures on a separate cohort of WT (n = 4) mice. Results: The mean percentage standard deviation among repeated measures was 10.1% for PWV and 24.8% for WSS. The PWV of ApoE-KO mice (5.84 ± 2.15 m/s) was signifi-cantly higher (p = 0.02) than that of WT (3.55 ± 0.97 m/s), whereas WSS was lower in ApoE-KO mice (1.44 ± 0.31Pa) compared with WT (1.55 ± 0.36Pa). Conclusion: This study demonstrates that in vivo PWV derived from radial phase contrast MR imaging can be potentially used as a surrogate marker for impaired vascular function in mice.