Reliability of magnetic resonance elastography using multislice two‐dimensional spin‐echo echo‐planar imaging (SE‐EPI) and three‐dimensional inversion reconstruction for assessing renal stiffness

Low, Gavin; Owen, Nicola; Joubert, Ilse; Patterson, Andrew J.; Graves, Martin J.; Glaser, Kevin J.; Alexander, Graeme; Lomas, David J.

doi:10.1002/jmri.24826

Cited by 31 publications

(41 citation statements)

References 35 publications

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“…First, we did not assess SE-EPI-MRE performance for detection and staging of liver fibrosis, which was not the aim of this study. Second, although we have limited data on test-retest analysis (n=4), we observed equivalent repeatability to that reported for SE-EPI-MRE in the kidney (16), and for liver GRE-MRE (35–37). …”

Section: Discussionsupporting

confidence: 56%

“…While SE-EPI-MRE sequences have been available with FDA-approved commercial implementations of MRE for several years, there is only limited information on comparability with standard one directional motion encoding GRE-MRE sequence in the literature (16). All the published data using a SE-EPI-MRE sequence in the liver used a 3 directional motion encoding SE-EPI-MRE (17–19).…”

Section: Introductionmentioning

confidence: 99%

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Magnetic Resonance Elastography of the Liver

et al. 2016

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Objective To compare 2D gradient recalled echo (GRE) and 2D spin echo echoplanar imaging (SE-EPI) magnetic resonance elastography (MRE) sequences of the liver in terms of image quality and quantitative liver stiffness (LS) measurement. Materials and methods This prospective study involved 50 consecutive subjects (M/F 33/17, mean age 58 y) who underwent liver MRI at 3.0T including two MRE sequences, 2D GRE and 2D SE-EPI (acquisition time 56 vs 16 s, respectively). Image quality scores were assessed by two independent observers based on wave propagation and organ coverage on the confidence map (range 0–15). A third observer measured LS on stiffness maps (in kPa). Mean LS values, ROI size (based on confidence map) and image quality scores between SE-EPI and GRE-MRE were compared using paired nonparametric Wilcoxon test. Reproducibility of LS values between the two sequences was assessed using intraclass coefficient correlation (ICC), coefficient of variation (CV) and Bland-Altman limits of agreement (BALA). T2* effect on image quality was assessed using partial Spearman correlation. Results There were 4 cases of failure with GRE-MRE and none with SE-EPI-MRE. Image quality scores and ROI size were significantly higher using SE-EPI-MRE vs. GRE-MRE (p <0.0001 for both measurements and observers). LS measurements were not significantly different between the two sequences (3.75 ± 1.87 vs. 3.51 ± 1.53 kPa, p=0.062), were significantly correlated (ICC=0.909) and had excellent reproducibility (CV=10.2%, bias=0.023, BALA −1.19; 1.66 kPa). Image quality scores using GRE-MRE were significantly correlated with T2*, while there was no correlation for SE-EPI-MRE. Conclusion Our data suggest that suggest that SE-EPI-MRE may be a better alternative to GRE-MRE. The diagnostic performance of SE-EPI-MRE for detection of liver fibrosis needs to be assessed in a future study.

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Section: Discussionsupporting

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Magnetic Resonance Elastography of the Liver

et al. 2016

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“…Unbalanced four‐point encoding encodes along three orthogonal encoding directions and corrects for imaging gradients by the measurement of a single reference phase image without motion sensitization . Six‐point encoding inverts each motion encoding gradient (MEG) to pairwise correct for imaging gradient offsets, thereby increasing DNR by two‐fold at the cost of a 50% longer scan duration compared with unbalanced four‐point encoding . A non‐orthogonal balanced four‐point encoding scheme has also been reported and is referred to as ‘tetrahedral encoding’, which encodes along the four diagonals of a regular cube.…”

Section: Introductionmentioning

confidence: 99%

Analysis and improvement of motion encoding in magnetic resonance elastography

et al. 2018

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Magnetic resonance elastography (MRE) utilizes phase contrast magnetic resonance imaging (MRI), which is phase locked to externally generated mechanical vibrations, to measure the three-dimensional wave displacement field. At least four measurements with linear-independent encoding directions are necessary to correct for spurious phase contributions if effects from imaging gradients are non-negligible. In MRE, three encoding schemes have been used: unbalanced four- and six-point and balanced four-point ('tetrahedral') encoding. The first two sensitize to motion with orthogonal gradients, with the four-point method acquiring a single reference scan without motion sensitization, whereas three additional scans with inverted gradients are used with six-point encoding, leading to two-fold higher displacement-to-noise ratio (DNR) and 50% longer scan duration. Balanced four-point (tetrahedral) encoding encodes along the four diagonals of a cube, with one direction serving as a reference for the other three encoding directions, similar to four-point encoding. The objective of this work is to introduce a theoretical framework to compare different motion sensitization strategies with respect to their motion encoding efficiency in two fundamental encoding limits, the gradient strength limit and the dynamic range limit, which are both placed in relation to conventional gradient recalled echo (GRE)- and spin echo (SE)-based MRE sequences. We apply the framework to the three aforementioned schemes and show that the motion encoding efficiency of unbalanced four- and six-point encoding schemes in the gradient-limited regime can be increased by a factor of 1.5 when using all physical gradient channels concurrently. Furthermore, it is demonstrated that reversing the direction of the reference in balanced four-point (tetrahedral) encoding results in the Hadamard encoding scheme, which leads to increased DNR by 2 compared with balanced four-point encoding and 2.8 compared with unbalanced four-point encoding. As an example, we show that optimal encoding can be utilized to reduce the acquisition time of standard liver MRE in vivo from four to two breath holds.

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“…MRE shows promise as a suitable alternative to mammography for the detection of breast cancer . In the brain, MRE can provide additional insights into neurological diseases and brain tumors and has been applied to other organs as well such as the prostate, the spleen, the kidney, and the heart …”

Section: Introductionmentioning

confidence: 99%

Encoding and readout strategies in magnetic resonance elastography

Guenthner

Kozerke

2018

NMR in Biomedicine

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Magnetic resonance elastography (MRE) has evolved significantly since its inception. Advances in motion-encoding gradient design and readout strategies have led to improved encoding and signal-to-noise ratio (SNR) efficiencies, which in turn allow for higher spatial resolution, increased coverage, and/or shorter scan times. The purpose of this review is to summarize MRE wave-encoding and readout approaches in a unified mathematical framework to allow for a comparative assessment of encoding and SNR efficiency of the various methods available. Besides standard full- and fractional-wave-encoding approaches, advanced techniques including flow compensation, sample interval modulation and multi-shot encoding are considered. Signal readout using fast k-space trajectories, reduced field of view, multi-slice, and undersampling techniques are summarized and put into perspective. The review is concluded with a foray into displacement and diffusion encoding as alternative and/or complementary techniques.

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Reliability of magnetic resonance elastography using multislice two‐dimensional spin‐echo echo‐planar imaging (SE‐EPI) and three‐dimensional inversion reconstruction for assessing renal stiffness

Cited by 31 publications

References 35 publications

Magnetic Resonance Elastography of the Liver

Magnetic Resonance Elastography of the Liver

Analysis and improvement of motion encoding in magnetic resonance elastography

Encoding and readout strategies in magnetic resonance elastography

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