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  • 1
    Online Resource
    Online Resource
    Estimation of global aortic pulse wave velocity by flow‐sensitive 4D MRI
    Wiley ; 2010
    In:  Magnetic Resonance in Medicine Vol. 63, No. 6 ( 2010-06), p. 1575-1582
    Details
    In: Magnetic Resonance in Medicine, Wiley, Vol. 63, No. 6 ( 2010-06), p. 1575-1582
    Abstract: The aim of this study was to determine the value of flow‐sensitive four‐dimensional MRI for the assessment of pulse wave velocity as a measure of vessel compliance in the thoracic aorta. Findings in 12 young healthy volunteers were compared with those in 25 stroke patients with aortic atherosclerosis and an age‐matched normal control group ( n = 9). Results from pulse wave velocity calculations incorporated velocity data from the entire aorta and were compared to those of standard methods based on flow waveforms at only two specific anatomic landmarks. Global aortic pulse wave velocity was higher in patients with atherosclerosis (7.03 ± 0.24 m/sec) compared to age‐matched controls (6.40 ± 0.32 m/sec). Both were significantly ( P 〈 0.001) increased compared to younger volunteers (4.39 ± 0.32 m/sec). Global aortic pulse wave velocity in young volunteers was in good agreement with previously reported MRI studies and catheter measurements. Estimation of measurement inaccuracies and error propagation analysis demonstrated only minor uncertainties in measured flow waveforms and moderate relative errors below 16% for aortic compliance in all 46 subjects. These results demonstrate the feasibility of pulse wave velocity calculation based on four‐dimensional MRI data by exploiting its full volumetric coverage, which may also be an advantage over standard two‐dimensional techniques in the often‐distorted route of the aorta in patients with atherosclerosis. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
    Type of Medium: Online Resource
    ISSN: 0740-3194 , 1522-2594
    URL: Issue
    URL: Article
    DOI: 10.1002/mrm.v63:6
    DOI: 10.1002/mrm.22353
    Language: English
    Publisher: Wiley
    Publication Date: 2010
    detail.hit.zdb_id: 1493786-4
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  • 2
    Online Resource
    Online Resource
    Reproducibility of flow and wall shear stress analysis using flow‐sensitive four‐dimensional MRI
    Wiley ; 2011
    In:  Journal of Magnetic Resonance Imaging Vol. 33, No. 4 ( 2011-04), p. 988-994
    Details
    In: Journal of Magnetic Resonance Imaging, Wiley, Vol. 33, No. 4 ( 2011-04), p. 988-994
    Abstract: 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. J. Magn. Reson. Imaging 2011;33:988–994. © 2011 Wiley‐Liss, Inc.
    Type of Medium: Online Resource
    ISSN: 1053-1807 , 1522-2586
    URL: Issue
    URL: Article
    DOI: 10.1002/jmri.v33.4
    DOI: 10.1002/jmri.22519
    Language: English
    Publisher: Wiley
    Publication Date: 2011
    detail.hit.zdb_id: 1497154-9
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  • 3
    Online Resource
    Online Resource
    Analysis of pulse wave velocity in the thoracic aorta by flow‐sensitive four‐dimensional MRI: Reproducibility and correlation with characteristics in patients with aortic atherosclerosis
    Wiley ; 2012
    In:  Journal of Magnetic Resonance Imaging Vol. 35, No. 5 ( 2012-05), p. 1162-1168
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    In: Journal of Magnetic Resonance Imaging, Wiley, Vol. 35, No. 5 ( 2012-05), p. 1162-1168
    Abstract: To measure aortic pulse wave velocity (PWV) using flow‐sensitive four‐dimensional (4D) MRI and to evaluate test–retest reliability, inter‐ and intra‐observer variability in volunteers and correlation with characteristics in patients with aortic atherosclerosis. Materials and Methods: Flow‐sensitive 4D MRI was performed in 12 volunteers (24 ± 3 years) and 86 acute stroke patients (68 ± 9 years) with aortic atherosclerosis. Retrospectively positioned 28 ± 4 analysis planes along the entire aorta (inter‐slice‐distance = 10 mm) and frame wise lumen segmentation yielded flow‐time‐curves for each plane. Global aortic PWV was calculated from time‐shifts and distances between the upslope portions of all available flow‐time curves. Results: Inter‐ and intra‐observer variability of PWV measurements in volunteers (7% and 8%) was low while test–retest reliability (22%) was moderate. PWV in patients was significantly higher compared with volunteers (5.8 ± 2.9 versus 3.8 ± 0.8 m/s; P = 0.02). Among 17 patient characteristics considered, statistical analysis revealed significant ( P 〈 0.05) but low correlation of PWV with age ( r = 0.25), aortic valve insufficiency ( r = 0.29), and pulse pressure ( r = 0.28). Multivariate modeling indicated that aortic valve insufficiency and elevated pulse pressure were significantly associated with higher PWV (adjusted R 2 = 0.13). Conclusion: Flow‐sensitive 4D MRI allows for estimating aortic PWV with low observer dependence and moderate test–retest reliability. PWV in patients correlated with age, aortic valve insufficiency, and pulse pressure. J. Magn. Reson. Imaging 2012;35:1162‐1168. © 2012 Wiley Periodicals, Inc.
    Type of Medium: Online Resource
    ISSN: 1053-1807 , 1522-2586
    URL: Issue
    URL: Article
    DOI: 10.1002/jmri.v35.5
    DOI: 10.1002/jmri.22856
    Language: English
    Publisher: Wiley
    Publication Date: 2012
    detail.hit.zdb_id: 1497154-9
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  • 4
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    3D MRI provides improved visualization and detection of aortic arch plaques compared to transesophageal echocardiography
    Wiley ; 2012
    In:  Journal of Magnetic Resonance Imaging Vol. 36, No. 3 ( 2012-09), p. 604-611
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    In: Journal of Magnetic Resonance Imaging, Wiley, Vol. 36, No. 3 ( 2012-09), p. 604-611
    Abstract: To compare 3D magnetic resonance imaging (3D MRI) with transesophageal echocardiography (TEE) for the detection of complex aortic plaques (≥4 mm thick, ulcerated, or containing mobile thrombi). Materials and Methods: In all, 99 consecutive patients with acute cryptogenic stroke and ≥3 mm thick aortic plaques in TEE were prospectively included. 3D MRI comprised T1‐weighted bright blood MRI with complete aortic coverage (spatial resolution 1 mm 3 ). Wall thickness and occurrence of complex plaques in ascending aorta (AAo), aortic arch (AA), and descending aorta (DAo) and image quality for each segment was rated for MRI and TEE. Results: MRI detected more complex plaques than TEE (MRI vs. TEE): AAo 13 vs. 7; AA 37 vs. 11; differences were smaller in the DAo: 101 vs. 70. Image quality was higher for MRI in AAo and AA ( P 〈 0.001) and superior for TEE in DAo ( P 〈 0.001). MRI revealed additional complex plaques in the proximal aorta in 19 of 58 patients (32.8%) categorized as cryptogenic after complete routine diagnostics including TEE. Conclusion: Due to improved visualization of the aorta 3D MRI allows to detect more complex plaques than TEE. This renders 3D MRI particularly valuable for patients with cryptogenic stroke and for trials evaluating optimal treatment in aortic atherosclerosis. J. Magn. Reson. Imaging 2012;36:604–611. © 2012 Wiley Periodicals, Inc.
    Type of Medium: Online Resource
    ISSN: 1053-1807 , 1522-2586
    URL: Issue
    URL: Article
    DOI: 10.1002/jmri.v36.3
    DOI: 10.1002/jmri.23679
    Language: English
    Publisher: Wiley
    Publication Date: 2012
    detail.hit.zdb_id: 1497154-9
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  • 5
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    Online Resource
    Flow‐sensitive 4D MRI of the thoracic aorta: Comparison of image quality, quantitative flow, and wall parameters at 1.5 T and 3 T
    Wiley ; 2012
    In:  Journal of Magnetic Resonance Imaging Vol. 36, No. 5 ( 2012-11), p. 1097-1103
    Details
    In: Journal of Magnetic Resonance Imaging, Wiley, Vol. 36, No. 5 ( 2012-11), p. 1097-1103
    Abstract: To evaluate the effect of field strength on flow‐sensitive 4D magnetic resonance imaging (MRI) of the thoracic aorta. A volunteer study at 1.5 T and 3 T was conducted to compare phase‐contrast MR angiography (MRA) and 3D flow visualization quality as well as quantification of aortic hemodynamics. Materials and Methods: Ten healthy volunteers were examined by flow‐sensitive 4D MRI at both 1.5 T and 3 T MRI with identical imaging parameters (TE/TR = 6/5.1 msec, spatial/temporal resolution ≈2 mm/40.8 msec). Analysis included assessment of image quality of derived aortic 3D phase contrast (PC) angiography and 3D flow visualization (semiquantitative grading on a 0–2 scale, two blinded observers) and quantification of blood flow velocities, net flow per cardiac cycle, wall shear stress (WSS), and velocity noise. Results: Quality of 3D blood flow visualization (average grading = 1.8 ± 0.4 at 3 T vs. 1.1 ± 0.7 at 1.5 T) and the depiction of aortic lumen geometry by 3D PC‐MRA (1.7 ± 0.5 vs. 1.2 ± 0.6) were significantly ( P 〈 0.01) improved at 3 T while velocity noise was significantly higher ( P 〈 0.01) at 1.5 T. Velocity quantification resulted in minimally altered (0.05 m/s, 3 mL/cycle and 0.01 N/m 2 ) but not statistically different ( P = 0.40, P = 0.39, and P = 0.82) systolic peak velocities, net flow, and WSS for 1.5 T compared to 3 T. Conclusion: Flow‐sensitive 4D MRI at 3 T provided improved image quality without additional artifacts related to higher fields. Imaging at 1.5 T MRI, which is more widely available, was also feasible and provided information on aortic 3D hemodynamics of moderate quality with identical performance regarding quantitative analysis. J. Magn. Reson. Imaging 2012;36:1097–1103. © 2012 Wiley Periodicals, Inc.
    Type of Medium: Online Resource
    ISSN: 1053-1807 , 1522-2586
    URL: Issue
    URL: Article
    DOI: 10.1002/jmri.v36.5
    DOI: 10.1002/jmri.23735
    Language: English
    Publisher: Wiley
    Publication Date: 2012
    detail.hit.zdb_id: 1497154-9
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