Phase-contrast magnetic resonance imaging for the evaluation of wall shear stress in the common carotid artery of a spontaneously hypertensive rat model at 7 T: Location-specific change, regional distribution along the vascular circumference, and reproducibility analysis

Purpose: To measure wall shear stress (WSS) in the common carotid arteries (CCA) of a spontaneously hypertensive rat (SHR) model and a normotensive Wistar Kyoto rat (WKY) model by 2D phase-contrast magnetic resonance imaging (PC-MRI). Materials and methods: PC-MRI was performed on 7 SHR and 7 WKY at ages of 4 and 7 months at a 7 T scanner. Images in the middle CCA (CCA_mid) and in the bifurcation of CCA (CCA_bifur) were acquired. The WSS values for differentiating characteristics between two models were calculated. Further, its location-specific change, regional distribution along the CCA circumference, and the reproducibility were evaluated. Results: In the 4-month-old rats, SHR showed lower temporal averaged WSS (WSS_avg) and peak systolic WSS (WSS_s) in the CCA_bifur in comparison with WKY (WSS_avg: 0.95 ± 0.18 vs. 1.30 ± 0.36 N/m² (P < 0.01); WSS_s: 1.68 ± 0.70 vs. 3.22 ± 2.49 N/m² (P < 0.05)). We observed the same trends in the 7-month-old rats. In the SHR model, the WSS_avg was lower in the CCA_bifur than in the CCA_mid. The regional distribution of WSS_avg along the circumference of CCA showed lower values in WKY, particularly in posterior segments of CCA_bifur. The intra-observer, intra-scan and inter-scan reproducibility was acceptable and the disagreements were ranged from -0.05 to 0.06 N/m². Conclusion: This study evaluated WSS in SHR and WKY models by 2D PC-MRI. High reproducibility analyses further indicated the reliability of measurements of WSS in the CCA of SHR and WKY models using PC-MRI at 7 T.