Dataset Information

Efficient triple-VENC phase-contrast MRI for improved velocity dynamic range.

ABSTRACT: PURPOSE:To evaluate the utility of an efficient triple velocity-encoding (VENC) 4D flow MRI implementation to improve velocity unwrapping of 4D flow MRI data with the same scan time as an interleaved dual-VENC acquisition. METHODS:A balanced 7-point acquisition was used to derive 3 sets of 4D flow images corresponding to 3 different VENCs. These 3 datasets were then used to unwrap the aliased lowest VENC into a minimally aliased, triple-VENC dataset. Triple-VENC MRI was evaluated and compared with dual-VENC MRI over 3 different VENC ranges (50-150, 60-150, and 60-180 cm/s) in vitro in a steadily rotating phantom as well as in a pulsatile flow phantom. In vivo, triple-VENC data of the thoracic aorta were also evaluated in 3 healthy volunteers (2 males, 26-44 years old) with VENC = 50/75/150 cm/s. Two triple-VENC (triconditional and biconditional) and 1 dual-VENC unwrapping algorithms were quantitatively assessed through comparison to a reference, unaliased, single-VENC scan. RESULTS:Triple-VENC 4D flow constant rotation phantom results showed high correlation with the analytical solution (intraclass correlation coefficient = 0.984-0.995, P < .001) and up to a 61% reduction in velocity noise compared with the corresponding single-VENC scans (VENC = 150, 180 cm/s). Pulsatile flow phantom experiments demonstrated good agreement between triple-VENC and single-VENC acquisitions (peak flow < 0.8% difference; peak velocity < 11.7% difference). Triconditional triple-VENC unwrapping consistently outperformed dual-VENC unwrapping, correctly unwrapping more than 83% and 46%-66% more voxels in vitro and in vivo, respectively. CONCLUSION:Triple-VENC 4D flow MRI adds no additional scan time to dual-VENC MRI and has the potential for improved unwrapping to extend the velocity dynamic range beyond dual-VENC methods.

SUBMITTER: Ma LE

PROVIDER: S-EPMC7051107 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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Efficient triple-VENC phase-contrast MRI for improved velocity dynamic range.

Ma Liliana E LE Markl Michael M Chow Kelvin K Vali Alireza A Wu Can C Schnell Susanne S

Magnetic resonance in medicine 20190818 2

<h4>Purpose</h4>To evaluate the utility of an efficient triple velocity-encoding (VENC) 4D flow MRI implementation to improve velocity unwrapping of 4D flow MRI data with the same scan time as an interleaved dual-VENC acquisition.<h4>Methods</h4>A balanced 7-point acquisition was used to derive 3 sets of 4D flow images corresponding to 3 different VENCs. These 3 datasets were then used to unwrap the aliased lowest VENC into a minimally aliased, triple-VENC dataset. Triple-VENC MRI was evaluated ...[more]

PMID: 31423646

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Project description:PurposeTo improve velocity-to-noise ratio (VNR) and dynamic velocity range of 4D flow magnetic resonance imaging (MRI) by using dual-velocity encoding (dual-venc) with k-t generalized autocalibrating partially parallel acquisition (GRAPPA) acceleration.Materials and methodsA dual-venc 4D flow MRI sequence with k-t GRAPPA acceleration was developed using a shared reference scan followed by three-directional low- and high-venc scans (repetition time / echo time / flip angle = 6.1 msec / 3.4 msec / 15°, temporal/spatial resolution = 43.0 msec/1.2 × 1.2 × 1.2 mm3 ). The high-venc data were used to correct for aliasing in the low-venc data, resulting in a single dataset with the favorable VNR of the low-venc but without velocity aliasing. The sequence was validated with a 3T MRI scanner in phantom experiments and applied in 16 volunteers to investigate its feasibility for assessing intracranial hemodynamics (net flow and peak velocity) at the major intracranial vessels. In addition, image quality and image noise were assessed in the in vivo acquisitions.ResultsAll 4D flow MRI scans were acquired successfully with an acquisition time of 20 ± 4 minutes. The shared reference scan reduced the total acquisition time by 12.5% compared to two separate scans. Phantom experiments showed 51.4% reduced noise for dual-venc compared to high-venc and an excellent agreement of velocities (ρ = 0.8, P < 0.001). The volunteer data showed decreased noise in dual-venc data (54.6% lower) compared to high-venc, and improved image quality, as graded by two observers: fewer artifacts (P < 0.0001), improved vessel conspicuity (P < 0.0001), and reduced noise (P < 0.0001).ConclusionDual-venc 4D flow MRI exhibits the superior VNR of the low-venc acquisition and reliably incorporates low- and high-velocity fields simultaneously. In vitro and in vivo data demonstrate improved flow visualization, image quality, and image noise.Level of evidence2 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:102-114.

Project description:BACKGROUND:Strain rate (SR) is a measure of the rate of regional deformation that can be computed by analyzing velocity-encoded phase-contrast 2D images. Recent studies have explored the changes in normal components of the strain tensor in aging muscle, while shear strain may also provide valuable information. PURPOSE:To compute the shear SR from velocity-encoded MRI of the lower leg and to study the correlation of SR parameters measured in the medial gastrocnemius (MG) to muscle force in a cohort of young and senior subjects. STUDY TYPE:Prospective cohort study. SUBJECTS:Six young (26.1?±?2.3 years) and six senior (76.7?±?8.3 years) healthy females; two other subjects were scanned on three separate occasions for repeatability studies. FIELD STRENGTH/SEQUENCE:1.5T using a single oblique sagittal slice with velocity-encoding in three directions (velocity-encoded phase contrast gradient echo sequence). ASSESSMENT:Age-related and regional differences in the SR eigenvalues (SRfiber , SRin-plane ), normal SRs (SRff , SRcc ), and shear SRs (SRfc , SRfc_max ) were statistically analyzed. STATISTICAL TESTS:Difference between young and senior cohorts were assessed using two-way analysis of variance (ANOVAs). The coefficient of variation and repeatability coefficient were calculated from repeat studies. Univariate and stepwise multivariable linear regression was performed to identify predictors of force. RESULTS:During isometric plantarflexion contraction, SRs in the principal basis (SRfiber , SRin-plane ) and maximum shear SR (SRfc_max ) was significantly lower in the senior cohort (P < 0.05). On multiple variable regression, maximum shear SR (SRfc_max ) and normal SR in the fiber cross-section (SRcc ) were significantly associated with force (R?=?0.681, F?=?14.034, P < 0.001). DATA CONCLUSION:This study establishes that computation of shear strain is feasible and is a significant predictor of force variability with age. LEVEL OF EVIDENCE:2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1351-1357.

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Efficient triple-VENC phase-contrast MRI for improved velocity dynamic range.

Publications

Efficient triple-VENC phase-contrast MRI for improved velocity dynamic range.

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