TY  - JOUR
A1  - Winter, Patrick
A1  - Andelovic, Kristina
A1  - Kampf, Thomas
A1  - Gutjahr, Fabian Tobias
A1  - Heidenreich, Julius
A1  - Zernecke, Alma
A1  - Bauer, Wolfgang Rudolf
A1  - Jakob, Peter Michael
A1  - Herold, Volker
T1  - Fast self-navigated wall shear stress measurements in the murine aortic archusing radial 4D-phase contrast cardiovascular magnetic resonance at 17.6 T
JF  - Journal of Cardiovascular Magnetic Resonance
N2  - 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.
KW  - 4D flow
KW  - WSS
KW  - OSI
KW  - Self-navigation
KW  - Mouse
KW  - Aortic arch
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-201120
VL  - 21
ER  - 
TY  - JOUR
A1  - Herold, Volker
A1  - Kampf, Thomas
A1  - Jakob, Peter Michael
T1  - Dynamic magnetic resonance scattering
JF  - Communications Physics
N2  - Dynamic light scattering is a popular technique to determine the size distribution of small particles in the sub micrometer region. It operates in reciprocal space, by analyzing the signal fluctuations with the photon auto correlation function. Equally, pulsed field gradient magnetic resonance is a technique generating data in the reciprocal space of the density distribution of an object. Here we show the feasibility of employing a magnetic resonance imaging system as a dynamic scattering device similar to dynamic light scattering appliances. By acquiring a time series of single data points from reciprocal space, analogue to dynamic light scattering, we demonstrate the examination of motion patterns of microscopic particles. This method allows the examination of particle dynamics significantly below the spatial resolution of magnetic resonance imaging. It is not limited by relaxation times and covers a wide field of applications for particle or cell motion in opaque media.
KW  - Characterization and analytical techniques
KW  - Imaging techniques
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-201091
VL  - 2
ER  -