Magnetic field shimming of a permanent magnet using a combination of pieces of permanent magnets and a single-channel shim coil for skeletal age assessment of children

Terada, Yasuhiko; Kono, Saki; Ishizawa, K.; Inamura, Shingo; Uchiumi, Tomomi; Tamada, Daiki; Kose, Katsumi

doi:10.1016/j.jmr.2013.02.005

Cited by 20 publications

(12 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We described the hardware specifications in a previous study. 8 Briefly, the MR imaging system consists of a C-shaped neodymium iron boron (Nd-Fe-B) permanent magnet, solenoid-type radiofrequency probe, gradient coil set, and MR imaging console. The specifications of the magnet circuit were: field strength, 0.3T; gap width, 12 cm; weight, 450 kg; size, 52 cm (width) © 62 cm (depth) © 52 cm (height) including a thermal shield; and homogeneity, 16 ppm over a 12 © 16 © 5-cm diameter ellipsoidal volume.…”

Section: Mr Examinationsmentioning

confidence: 99%

See 1 more Smart Citation

Improved Reliability in Skeletal Age Assessment using a Pediatric Hand MR Scanner with a 0.3T Permanent Magnet

et al. 2014

View full text Add to dashboard Cite

The purpose of this study was to improve the reliability and validity of skeletal age assessment using an open and compact pediatric hand magnetic resonance (MR) imaging scanner. We used such a scanner with 0.3-tesla permanent magnet to image the left hands of 88 healthy children (aged 3.4 to 15.7 years, mean 8.8 years), and 3 raters (2 orthopedic specialists and a radiologist) assessed skeletal age using those images. We measured the strength of agreement in ratings by values of weighted Cohen's ¬ and the proportion of cases excluded from rating because of motion artifact and inappropriate positioning. We compared the current results with those of a previous study in which 93 healthy children (aged 4.1 to 16.4 years, mean 9.7 years) were examined with an adult hand scanner. The ¬ values between raters exceeded 0.80, which indicates almost perfect agreement, and most were higher than those of the previous study. The proportion of cases excluded from rating because of motion artifact or inappropriate positioning was also reduced. The results indicate that use of the compact pediatric hand scanner improved the reliability and validity of skeletal age assessments.

show abstract

Section: Mr Examinationsmentioning

confidence: 99%

“…To remedy this problem, we developed a new pediatric hand scanner with a smaller permanent magnet 8 that enhances the openness and compactness of the system and allows examination in a more comfortable position. Using this system, we showed sufficient image quality of the left hand of a 4.9-year-old volunteer for skeletal age assessment.…”

Section: Introductionmentioning

confidence: 99%

Improved Reliability in Skeletal Age Assessment using a Pediatric Hand MR Scanner with a 0.3T Permanent Magnet

et al. 2014

View full text Add to dashboard Cite

show abstract

“…[43][44][45] Elsewhere, 0.3 T magnets have been used to compare D-T 2 correlations with permeability estimates calculated from X-ray microcomputed tomography (μCT) images, 46 to image drop shapes for interfacial tension measurements, 47 to monitor cement paste hydration, 48 to measure gas dispersion coefficients, 21 and to conduct clinical investigations of human hands. 49 In the present work, fast imaging techniques drawn from the medical literature are applied to saturated rock plugs with long T 1 and T 2 relaxation times to demonstrate the range of imaging modalities available at this field strength.…”

Section: Introductionmentioning

confidence: 99%

Contributed Review: Nuclear magnetic resonance core analysis at 0.3 T

Mitchell

Fordham

2014

Review of Scientific Instruments

View full text Add to dashboard Cite

Nuclear magnetic resonance (NMR) provides a powerful toolbox for petrophysical characterization of reservoir core plugs and fluids in the laboratory. Previously, there has been considerable focus on low field magnet technology for well log calibration. Now there is renewed interest in the study of reservoir samples using stronger magnets to complement these standard NMR measurements. Here, the capabilities of an imaging magnet with a field strength of 0.3 T (corresponding to 12.9 MHz for proton) are reviewed in the context of reservoir core analysis. Quantitative estimates of porosity (saturation) and pore size distributions are obtained under favorable conditions (e.g., in carbonates), with the added advantage of multidimensional imaging, detection of lower gyromagnetic ratio nuclei, and short probe recovery times that make the system suitable for shale studies. Intermediate field instruments provide quantitative porosity maps of rock plugs that cannot be obtained using high field medical scanners due to the field-dependent susceptibility contrast in the porous medium. Example data are presented that highlight the potential applications of an intermediate field imaging instrument as a complement to low field instruments in core analysis and for materials science studies in general.

show abstract

“…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

230

266

View full text Add to dashboard Cite

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.

show abstract

Magnetic field shimming of a permanent magnet using a combination of pieces of permanent magnets and a single-channel shim coil for skeletal age assessment of children

Cited by 20 publications

References 43 publications

Improved Reliability in Skeletal Age Assessment using a Pediatric Hand MR Scanner with a 0.3T Permanent Magnet

Improved Reliability in Skeletal Age Assessment using a Pediatric Hand MR Scanner with a 0.3T Permanent Magnet

Contributed Review: Nuclear magnetic resonance core analysis at 0.3 T

Low‐field MRI: An MR physics perspective

Contact Info

Product

Resources

About