A permanent MRI magnet for magic angle imaging having its field parallel to the poles

McGinley, John V.M.; Ristić, M.; Young, I. R.

doi:10.1016/j.jmr.2016.08.001

Cited by 16 publications

(9 citation statements)

References 17 publications

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“…In conventional open scanners, in which the field is perpendicular to the poles, it is possible to rotate the magnet about 1 axis to rotate the field, but rotation about the second axis is restricted by the patient, and magnet rotation about the z‐axis will not change the direction of the field. For these reasons, we have proposed a new type of open MRI magnet in which the field is parallel to the poles and can be rotated about 2 axes while the subject remains stationary.…”

Section: Discussionmentioning

confidence: 99%

“…Our future work will be directed toward obtaining equivalent MRI results in vivo. This necessitates the use of new MRI scanner types such as the transverse field open magnet currently under development in our labs . As this is a low‐field machine, it faces the challenge of achieving images with a sufficiently high SNR.…”

Section: Discussionmentioning

confidence: 99%

“…The AI was found to be a useful measure for quantitative assessment of fiber structure anisotropy, which may be useful in the future to establish diagnostic criteria and to augment the visual analysis of 3D tractography data. Application of the method to human imaging will demand the use of new magnet configurations, such as that proposed in McGinley et al, which are able to provide less restricted control of the field orientation to the subject than the conventional closed bore, or the conventional open MRI scanners.…”

Section: Discussionmentioning

confidence: 99%

“…The work presented in this paper was motivated by our continuing development of a novel transverse field MRI scanner, which was designed to enable imaging of this type to be performed in future in vivo human subjects. It uses a unique magnet configuration in which the net field is parallel to the poles.…”

Section: Introductionmentioning

confidence: 99%

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Detection of maturity and ligament injury using magic angle directional imaging

Chappell

Brujić

Straeten

et al. 2019

Magnetic Resonance in Med

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Purpose:To investigate whether magnetic field-related anisotropies of collagen may be correlated with postmortem findings in animal models. Methods: Optimized scan planning and new MRI data-processing methods were proposed and analyzed using Monte Carlo simulations. Six caprine and 10 canine knees were scanned at various orientations to the main magnetic field. Image intensities in segmented voxels were used to compute the orientation vectors of the collagen fibers. Vector field and tractography plots were computed. The Alignment Index was defined as a measure of orientation distribution. The knees were subsequently assessed by a specialist orthopedic veterinarian, who gave a pathological diagnosis after having dissected and photographed the joints. Results: Using 50% less scans than reported previously can lead to robust calculation of fiber orientations in the presence of noise, with much higher accuracy. The 6 caprine knees were found to range from very immature (< 3 months) to very mature (> 3 years). Mature specimens exhibited significantly more aligned collagen fibers in their patella tendons compared with the immature ones. In 2 of the 10 canine knees scanned, partial cranial caudal ligament tears were identified from MRI and subsequently confirmed with encouragingly high consistency of tractography, Alignment Index, and dissection results. Conclusion: This method can be used to detect injury such as partial ligament tears, and to visualize maturity-related changes in the collagen structure of tendons. It can provide the basis for new, noninvasive diagnostic tools in combination with new scanner configurations that allow less-restricted field orientations. K E Y W O R D Scollagen, magic angle effect, musculoskeletal imaging

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Detection of maturity and ligament injury using magic angle directional imaging

Chappell

Brujić

Straeten

et al. 2019

Magnetic Resonance in Med

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“…22,23 Electrical shim coils can also be used as an alternative method to optimize the field homogeneity. 24 In terms of research magnets, McGinley et al 25 have recently proposed a new permanent magnet design that produces a main magnetic field parallel (as opposed to the conventional perpendicular) to the pole pieces, which potentially allows rotation of the magnet with respect to the object. In this way, it is possible to obtain images with the so-called magic angle between the direction of the static magnetic field and the orientation of the structures of interest.…”

Section: Magnet Materialsmentioning

confidence: 99%

Low‐field MRI: An MR physics perspective

Marques

Simonis

Webb

2019

Magnetic Resonance Imaging

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266

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Historically, clinical MRI started with main magnetic field strengths in the ∼0.05–0.35T range. In the past 40 years there have been considerable developments in MRI hardware, with one of the primary ones being the trend to higher magnetic fields. While resulting in large improvements in data quality and diagnostic value, such developments have meant that conventional systems at 1.5 and 3T remain relatively expensive pieces of medical imaging equipment, and are out of the financial reach for much of the world. In this review we describe the current state‐of‐the‐art of low‐field systems (defined as 0.25–1T), both with respect to its low cost, low foot‐print, and subject accessibility. Furthermore, we discuss how low field could potentially benefit from many of the developments that have occurred in higher‐field MRI. In the first section, the signal‐to‐noise ratio (SNR) dependence on the static magnetic field and its impact on the achievable contrast, resolution, and acquisition times are discussed from a theoretical perspective. In the second section, developments in hardware (eg, magnet, gradient, and RF coils) used both in experimental low‐field scanners and also those that are currently in the market are reviewed. In the final section the potential roles of new acquisition readouts, motion tracking, and image reconstruction strategies, currently being developed primarily at higher fields, are presented. Level of Evidence : 5 Technical Efficacy Stage : 1 J. Magn. Reson. Imaging 2019.

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Imaging Instrumentation and Experiments

2022

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A permanent MRI magnet for magic angle imaging having its field parallel to the poles

Cited by 16 publications

References 17 publications

Detection of maturity and ligament injury using magic angle directional imaging

Detection of maturity and ligament injury using magic angle directional imaging

Low‐field MRI: An MR physics perspective

Imaging Instrumentation and Experiments

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