Multifrequency Magnetic Resonance Elastography of the Abdominal Aortic Wall: Segmental, Positional and Flow Effects

Current aortic magnetic-resonance-elastography (MRE) infers wall stiffness indirectly from waveguide effects. This study aimed to evaluate the feasibility of abdominal aortic MRE for direct assessment of wall stiffness and its dependence on segmental region, patient position, and hemodynamic parameters. This prospective study examined 11 healthy young male volunteers using MRE to evaluate two anatomical segments of the abdominal aorta: the supraceliac (SC) and infrarenal (IR) segments. The volunteers underwent examinations in both the supine and prone positions. An ECG trigger delay was implemented for MRE to minimize the blood signal in the lumen. Three-dimensional wavefields were acquired at three mechanical frequencies (70, 80, and 90 Hz), and shear wave speed (SWS) maps were reconstructed as a stiffness surrogate. In addition, blood flow-velocity MRI was performed assess hemodynamic parameters. Test-retest examinations were performed in a subgroup to evaluate repeatability of aortic MRE. Aortic wall MRE was successful in all participants with good repeatability (ICC = 0.76). Mean wall SWS was higher in SC than IR segments at supine (1.47 ± 0.07 vs. 1.39 ± 0.13 m/s, p = 0.035) and prone positions (1.40 ± 0.09 vs. 1.33 ± 0.10 m/s, p = 0.046) with higher values in supine SC segments (p = 0.019). Flow measurements revealed higher peak velocity and peak flow in SC than IR segments (all p < 0.001) with significant effects of examination position on peak velocity and cross-sectional area in SC (all p < 0.05). In prone position, peak velocity correlated negatively with aorta stiffness (SC: r = -0.75, p = 0.008; IR: r = -0.69, p = 0.019). This study demonstrated abdominal aortic MRE for directly depicting wall stiffness with minimal blood contribution. Segment-specific aortic wall stiffness was sensitive to circulatory loading and vascular distensibility. In a clinical context, high-resolution multifrequency MRE could serve as an imaging marker for vascular health and abdominal aortic risk stratification.