Quantification and comparison of 4D‐flow MRI‐derived wall shear stress and MRE‐derived wall stiffness of the abdominal aorta

Purpose Aortic wall shear stress (WSS Flow ) alters endothelial function, which in‐turn changes aortic wall stiffness leading to remodeling in different disease states. Therefore, the aims of this study are to determine normal physiologic correlations between: (1) Magnetic Resonance Elastography (MRE)‐derived aortic wall stiffness (WS MRE ) and WSS Flow ; (2) WS MRE and mean velocity; (3) WS MRE and pulse wave velocity (PWV);( 4) WS MRE and mean peak flow; and (5) WS MRE , WSS Flow and age using MRE and 4D‐flow MRI in the abdominal aorta in healthy human subjects. Materials and Methods Cardiac‐gated aortic MRE and 4D‐flow MRI data were acquired in 24 healthy volunteers using a 3 Tesla scanner. For MRE, 70 Hz external motion was applied to obtain wave images in all spatial directions in a separate breathhold. Whereas, 4D‐flow data was acquired under free‐breathing. Wave images in all the directions were processed to obtain three‐dimensional‐weighted stiffness map at end‐systole (ES). WSS Flow , mean velocity, PWV and mean peak flow were obtained using 4D‐flow data. Pearson correlation was performed to determine association between all variables. Results A significant negative correlation was observed between: (1) ES WS MRE and WSS Flow in both axial (r = ‐0.62; P = 0.006) and circumferential (r = ‐0.52; P = 0.016) directions; (2) ES WS MRE and mean velocity (r = ‐0.58; P = 0.012); and (3) age and WSS Flow in both axial (r = ‐0.71; P < 0.0001) and circumferential (r = ‐0.58; P = 0.0012) directions. A significant positive correlation was observed between: (1) ES WS MRE and PWV (r = 0.69; P < 0.0001); (2) ES WS MRE and mean peak flow (r = 0.53; P = 0.016); and (3) ES WS MRE and age (r = 0.63; P = 0.006). Conclusion The negative significant correlation between aortic WSS Flow and WS MRE in normal volunteers demonstrates a relationship between WS MRE and WSS Flow . Level of Evidence: 2 J. Magn. Reson. Imaging 2017;45:771–778.