Fast self-navigated wall shear stress measurements in the murine aortic arch using radial 4D-phase contrast cardiovascular magnetic resonance at 17.6 T

Abstract

Purpose 4D flow cardiovascular magnetic resonance (CMR) and the assessment of wall shear stress (WSS) are non-invasive tools to study cardiovascular risks in vivo. Major limitations of conventional triggered methods are the long measurement times needed for high-resolution data sets and the necessity of stable electrocardiographic (ECG) triggering. In this work an ECG-free retrospectively synchronized method is presented that enables accelerated high-resolution measurements of 4D flow and WSS in the aortic arch of mice. Methods 4D flow and WSS were measured in the aortic arch of 12-week-old wildtype C57BL/6 J mice (n = 7) with a radial 4D-phase-contrast (PC)-CMR sequence, which was validated in a flow phantom. Cardiac and respiratory motion signals were extracted from the radial CMR signal and were used for the reconstruction of 4D-flow data. Rigid motion correction and a first order B0 correction was used to improve the robustness of magnitude and velocity data. The aortic lumen was segmented semi-automatically. Temporally averaged and time-resolved WSS and oscillatory shear index (OSI) were calculated from the spatial velocity gradients at the lumen surface at 14 locations along the aortic arch. Reproducibility was tested in 3 animals and the influence of subsampling was investigated. Results Volume flow, cross-sectional areas, WSS and the OSI were determined in a measurement time of only 32 min. Longitudinal and circumferential WSS and radial stress were assessed at 14 analysis planes along the aortic arch. The average longitudinal, circumferential and radial stress values were 1.52 ± 0.29 N/m2, 0.28 ± 0.24 N/m2 and − 0.21 ± 0.19 N/m2, respectively. Good reproducibility of WSS values was observed. Conclusion This work presents a robust measurement of 4D flow and WSS in mice without the need of ECG trigger signals. The retrospective approach provides fast flow quantification within 35 min and a flexible reconstruction framework.

Wall shear stress analysis using 17.6 Tesla MRI: A longitudinal study in ApoE-/- mice with histological analysis

“…These findings are in accordance with the WSS values in this study compared to previous findings from Stalder et al [12]. The first step of longitudinal visualization of the WSS via a 2D imaging method is feasible in a high quality, thus, now the application of 3D acquisitions, as described in [37], in a longitudinal study is needed. However, the previous publication by Stalder et al [12] showed that a 3D measuring method underestimates the WSS values in comparison to a 2D measuring method.…”

Evaluation of Plaque Characteristics and Inflammation Using Magnetic Resonance Imaging

“…Therefore, accelerated techniques are needed in order to assess arterial wall shear stress values in reasonable measurement times. In 2019, a radial PC MRI sequence was presented that uses self-navigation and retrospective cine reconstruction for 4D flow measurements in the murine aortic arch [ 79 ]. Due to the strong signal enhancement of blood and suppression of undersampling artifacts, a scan time reduction to 35 min, and high spatial resolution (100 µm isotropic) were achievable.…”

“…These murine disease models are used to advance our mechanistic understanding of atherosclerosis—thus, there is a need to adapt these methods to the murine system. In 2019, our group presented a self-gated radial 4D flow MRI sequence that enabled high-resolution WSS measurements in 35 min [ 79 ]. However, combined measurements of both WSS and PWV are challenging since both parameters have different requirements for the temporal and spatial resolutions [ 76 ].…”

“… Four-dimensional (4D) flow and wall shear stress (WSS) measurements in the murine aortic arch. ( A ) Wall shear stress map of the aortic arch of an ApoE −/− mouse fed a Western diet, assessed with a self-gated radial 4D phase-contrast magnetic resonance imaging (PC-MRI) sequence [ 79 ]. Especially in the ascending aortic arch, a large region of low WSS can be observed in the inner curvature.…”

“…This area is known to be prone to plaque development. ( B ) Streamline presentation of the measured flow and through plane flow for 6 exemplary analysis planes, obtained from the same 4D flow measurement [ 79 , 80 ].…”