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- Fyrdahl, A., et al.
(author)
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Generalization of three-dimensional golden-angle radial acquisition to reduce eddy current artifacts in bSSFP CMR imaging
- 2021
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In: Magnetic Resonance Materials in Physics Biology and Medicine. - : Springer Science and Business Media LLC. - 0968-5243 .- 1352-8661. ; 34, s. 109-118
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Journal article (peer-reviewed)abstract
- Purpose We propose a novel generalization of the three-dimensional double-golden-angle profile ordering, which allows for whole-heart volumetric imaging with retrospective binning and reduced eddy current artifacts. Methods A novel theory bridging the gap between the three-dimensional double golden-angle trajectory, and the two-dimensional tiny-golden-angle trajectory is presented. This enables a class of double golden-angle profile orderings with a smaller angular distance between successivek-space readouts. The novel profile orderings were evaluated through simulations, phantom experiments, and in vivo imaging. Comparisons were made to the original double-golden-angle trajectory. Image uniformity and off-resonance sensitivity were evaluated using phantom measurements, and qualitative image quality was assessed using in vivo images acquired in a healthy volunteer. Results The proposed theory successfully reduced the angular step while maintaining image uniformity after binning. Simulations revealed a slow degradation with decreasing angular steps and an increasing number of physiological bins. The phantom images showed a definite improvement in image uniformity and increased robustness to off-resonance, and in vivo imaging corroborated those findings. Conclusion Reducing the angular step in cardio-respiratory-binned golden-angle imaging shows potential for overcoming eddy current-induced image artifacts associated with 3D golden-angle radial imaging.
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- Fyrdahl, A., et al.
(author)
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Sector-wise golden-angle phase contrast with high temporal resolution for evaluation of left ventricular diastolic dysfunction
- 2020
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In: Magnetic Resonance in Medicine. - : Wiley. - 0740-3194 .- 1522-2594. ; 83:4, s. 1310-1321
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Journal article (peer-reviewed)abstract
- Purpose To develop a high temporal resolution phase‐contrast pulse sequence for evaluation of diastolic filling patterns, and to evaluate it in comparison to transthoracic echocardiography. Methods A phase‐contrast velocity‐encoded gradient‐echo pulse sequence was implemented with a sector‐wise golden‐angle radial ordering. Acquisitions were optimized for myocardial tissue (TE/TR: 4.4/6.8 ms, flip angle: 8º, velocity encoding: 30 cm/s) and transmitral flow (TE/TR: 4.0/6.6 ms, flip angle: 20º, velocity encoding: 150 cm/s). Shared velocity encoding was combined with a sliding‐window reconstruction that enabled up to 250 frames per cardiac cycle. Transmitral and myocardial velocities were measured in 35 patients. Echocardiographic velocities were obtained with pulsed‐wave Doppler using standard methods. Results Myocardial velocity showed a low difference and good correlation between MRI and Doppler (mean ± 95% limits of agreement 0.9 ± 3.7 cm/s, R2 = 0.63). Transmitral velocity was underestimated by MRI (P < .05) with a difference of −11 ± 28 cm/s (R2 = 0.45). The early‐to‐late ratio correlated well (R2 = 0.66) with a minimal difference (0.03 ± 0.6). Analysis of interobserver and intra‐observer variability showed excellent agreement for all measurements. Conclusions The proposed method enables the acquisition of phase‐contrast images during a single breath‐hold with a sufficiently high temporal resolution to match transthoracic echocardiography, which opens the possibility for many clinically relevant variables to be assessed by MRI.
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- Kvitting, J.P., et al.
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Analysis of human myocardial dynamics using virtual markers based on magnetic resonance imaging
- 2010
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In: Clinical Physiology and Functional Imaging. - 1475-0961 .- 1475-097X. ; 30:1, s. 23-29
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Journal article (peer-reviewed)abstract
- Background: Myocardial dynamics are three-dimensional (3D) and time-varying. Cineradiography of surgically implanted makers in animals or patients is accurate for assessing these events, but this invasive method potentially alters myocardial motion. The aim of the study was to quantify myocardial motion using magnetic resonance imaging (MRI) and hence to provide a non-invasive approach to characterize 3D myocardial dynamics. Methods: Myocardial motion was quantified in ten normal volunteers by tracking the Lagrangian motion of individual points (i.e. virtual markers), based on time-resolved 3D phase-contrast MRI data and Fourier tracking. Nine points in the myocardium were tracked over the entire cardiac cycle, allowing a wire frame model to be generated and systolic and diastolic events identified. Results: Radius of curvature of the left ventricular (LV) wall was calculated from the virtual markers; the ratio between the anterior–posterior (AP) and septal–lateral (SL) walls in the LV shows an oval shape of the apical short axis plane at end systole (ES) and more circular at end diastole (ED). The AP/SL ratio for the basal plane shows an oval shape at ES and ED. We found that the rotation of the basal plane in ES was less compared to the apical plane [−2·0 ± 2·2 versus 4·1 ± 2·6 degrees (P<0·005)]. The apical plane rotated counter clock wise as viewed from the apex. Conclusion: This new non-invasive tool, despite current limitations in temporal and spatial resolution, may provide a comprehensive set of virtual myocardial markers throughout the entire LV without the confounding effects introduced by surgical implantation.
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- Ramos, J. G., et al.
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Comprehensive Cardiovascular Magnetic Resonance Diastolic Dysfunction Grading Shows Very Good Agreement Compared With Echocardiography
- 2020
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In: Jacc-Cardiovascular Imaging. - : Elsevier BV. - 1936-878X .- 1876-7591. ; 13:12, s. 2530-2542
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Journal article (peer-reviewed)abstract
- OBJECTIVES The aims of this study were to develop a comprehensive cardiovascular magnetic resonance (CMR) approach to diastolic dysfunction (DD) grading and to evaluate the accuracy of CMR in the diagnosis of DD compared with echocardiography. BACKGROUND Left ventricular DD is routinely assessed using echocardiography. METHODS Consecutive clinically referred patients (n = 46; median age 59 years; interquartile range: 46 to 68 years; 33% women) underwent both conventional echocardiography and CMR. CMR diastolic transmitral velocities (E and A) and myocardial tissue velocity (e0) were measured during breath-hold using a validated high-temporal resolution radial sector-wise golden-angle velocity-encoded sequence. CMR pulmonary artery pressure was estimated from 4-dimensional flow analysis of blood flow vortex duration in the pulmonary artery. CMR left atrial volume was measured using the biplane long-axis area-length method. Both CMR and echocardiographic data were used to perform blinded grading of DD according to the 2016 joint American and European recommendations. RESULTS Grading of DD by CMR agreed with that by echocardiography in 43 of 46 cases (93%), of which 9% were normal, 2% indeterminate, 63% grade 1 DD, 4% grade 2 DD, and 15% grade 3 DD. There was a very good categorical agreement, with a weighted Cohen kappa coefficient of 0.857 (95% confidence interval: 0.73 to 1.00; p < 0.001). CONCLUSIONS A comprehensive CMR protocol for grading DD encompassing diastolic blood and myocardial velocities, estimated pulmonary artery pressure, and left atrial volume showed very good agreement with echocardiography. (C) 2020 by the American College of Cardiology Foundation.
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