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  • Title: Reproducibility of flow and wall shear stress analysis using flow-sensitive four-dimensional MRI.
    Author: Markl M, Wallis W, Harloff A.
    Journal: J Magn Reson Imaging; 2011 Apr; 33(4):988-94. PubMed ID: 21448968.
    Abstract:
    PURPOSE: To systematically investigate the scan-rescan reproducibility and observer variability of flow-sensitive four-dimensional (4D) MRI in the aorta for the assessment of blood flow and global and segmental wall shear stress. MATERIALS AND METHODS: ECG and respiration-synchronized flow-sensitive 4D MRI data (spatio-temporal resolution = 1.7 × 2.0 × 2.2 mm(3) /40.8 ms) were acquired in 12 healthy volunteers. To analyze scan-rescan variability, flow-sensitive 4D MRI was repeated in 10 volunteers during a second visit. Data analysis included calculation of time-resolved and total flow, peak systolic velocity, and regional and global wall shear stress (WSS) in up to 24 analysis planes distributed along the aorta. RESULTS: Scan-rescan, inter-observer, and intra-observer agreement was excellent for the calculation of total flow and peak systolic velocity (mean differences <5% of the average flow parameter). Global WSS demonstrated moderate agreement and increased variability regarding wall shear stress (scan-rescan, inter-observer, and intra-observer agreement; mean differences <10% of the average WSS parameters). The segmental distribution of wall shear stress in the thoracic aorta could reliably be reproduced (r > 0.87; P < 0.001) for different observers and examinations. CONCLUSION: Flow-sensitive 4D MRI-based analysis of aortic blood flow can be performed with good reproducibility. Robustness of global and regional WSS quantification was limited, but spatio-temporal WSS distributions could reliably be replicated.
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