1
|
Yang L, Chen F, Chen L, Zhang Z, Chen J, Wang J, Cheng X, Feng J, Bao Q, Liu C. An easy-built Halbach magnet for LF-NMR with high homogeneity using optimized target-field passive shimming method. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 357:107582. [PMID: 37950959 DOI: 10.1016/j.jmr.2023.107582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 10/01/2023] [Accepted: 10/30/2023] [Indexed: 11/13/2023]
Abstract
The aim of this work is to develop a Halbach magnet that possesses characteristics such as easy-built, low cost and high homogeneity for use in a portable low-field NMR (LF-NMR) system. Considering portability, a 4-ring Halbach magnet was designed through simulation and mechanical modelling, which was successfully constructed in a general laboratory setting. The obtained field strength (B0) was 0.169 T, with an initial homogeneity of 8204 ppm within a sphere with a diameter of 20 mm. To enhance robustness, efficiency and effectiveness of shimming, an optimized target-field passive shimming method was proposed. Subsequently, the homemade spectrometer was used to run NMR experiments on the Halbach magnet. The 1H NMR linewidths of water samples became significantly narrower after passive shimming, e.g., the linewidth of a sample with a diameter of 3 mm and a length of 3 mm reduced from 452.3 Hz (62.5 ppm) to 12.9 Hz (1.8 ppm), which was much less than 102 Hz. The NMR results demonstrate that the proposed passive shimming method can achieve high homogeneity, and the developed Halbach magnet is capable of satisfying numerous LF-NMR applications.
Collapse
Affiliation(s)
- Lize Yang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Science, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Fang Chen
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Science, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Li Chen
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Science, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhi Zhang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Science, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Junfei Chen
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Science, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jiaxin Wang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Science, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xin Cheng
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Science, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jiwen Feng
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Science, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Qingjia Bao
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Science, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chaoyang Liu
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Science, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China; Optics Valley Laboratory, Wuhan 430074, China.
| |
Collapse
|
2
|
Webb A, O'Reilly T. Tackling SNR at low-field: a review of hardware approaches for point-of-care systems. MAGMA (NEW YORK, N.Y.) 2023:10.1007/s10334-023-01100-3. [PMID: 37202656 PMCID: PMC10386948 DOI: 10.1007/s10334-023-01100-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 05/03/2023] [Accepted: 05/09/2023] [Indexed: 05/20/2023]
Abstract
OBJECTIVE To review the major hardware components of low-field point-of-care MRI systems which affect the overall sensitivity. METHODS Designs for the following components are reviewed and analyzed: magnet, RF coils, transmit/receive switches, preamplifiers, data acquisition system, and methods for grounding and mitigating electromagnetic interference. RESULTS High homogeneity magnets can be produced in a variety of different designs including C- and H-shaped as well as Halbach arrays. Using Litz wire for RF coil designs enables unloaded Q values of ~ 400 to be reached, with body loss representing about 35% of the total system resistance. There are a number of different schemes to tackle issues arising from the low coil bandwidth with respect to the imaging bandwidth. Finally, the effects of good RF shielding, proper electrical grounding, and effective electromagnetic interference reduction can lead to substantial increases in image signal-to-noise ratio. DISCUSSION There are many different magnet and RF coil designs in the literature, and to enable meaningful comparisons and optimizations to be performed it would be very helpful to determine a standardized set of sensitivity measures, irrespective of design.
Collapse
Affiliation(s)
- Andrew Webb
- Department of Radiology, C.J. Gorter MRI Center, Leiden University Medical Center, 2333 ZA, Leiden, The Netherlands.
| | - Thomas O'Reilly
- Department of Radiology, C.J. Gorter MRI Center, Leiden University Medical Center, 2333 ZA, Leiden, The Netherlands
| |
Collapse
|
3
|
Yu P, Wang Y, Xu Y, Wu Z, Zhao Y, Peng B, Wang F, Tang Y, Yang X. Theoretical foundation for designing multilayer Halbach array magnets for benchtop NMR and MRI. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2022; 344:107322. [PMID: 36332512 DOI: 10.1016/j.jmr.2022.107322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 10/21/2022] [Accepted: 10/23/2022] [Indexed: 06/16/2023]
Abstract
Multilayer Halbach array magnets support portable NMR and MRI, but optimizing their design to maximize performance and minimize the use of expensive magnet materials is challenging. This is partly because our theoretical understanding of such arrays is incomplete and computationally intensive. Here we provide a theoretical description of the magnetic field distribution and we demonstrate that inhomogeneity is greatest along the z axis in multilayer Halbach array magnets. This allows the configuration of the multilayer Halbach array magnets to be optimized in a way that takes into account homogeneity, magnet volume, and magnetic flux density. At the same time, our description simplifies the design of multilayer array magnets, while accommodating the possibility of different outer radii, lengths for each layer array, or the presence of separation between the rings. We validated the theoretical description in simulations of a three-layer Halbach array magnet, then with a prototype three-layer 1-T Halbach array magnet. After adjusting the position of magnet blocks in the neighboring rings, we achieved homogeneity of 220 ppm for a standard 5 mm NMR tube while the inner diameter of the magnet is 20 mm. Our work provides a theoretical foundation for designing multilayer Halbach array magnets to maximize homogeneity and minimize the use of magnet materials.
Collapse
Affiliation(s)
- Peng Yu
- School of Biomedical Engineering (Suzhou), Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230026, China; Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, China; Jinan Guoke Medical Technology Development Co., Ltd., Jinan 250101, China
| | - Ya Wang
- School of Biomedical Engineering (Suzhou), Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230026, China; Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, China
| | - Yajie Xu
- Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, China
| | - Zhongyi Wu
- Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, China
| | - Ying Zhao
- Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, China
| | - Bowen Peng
- School of Biomedical Engineering (Suzhou), Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230026, China; Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, China
| | - Feng Wang
- School of Electronic and Information Engineering, Changchun University of Science and Technology, 130022 Changchun, China
| | - Yuguo Tang
- Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, China.
| | - Xiaodong Yang
- Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, China.
| |
Collapse
|
4
|
Abstract
Nuclear magnetic resonance at low field strength is an insensitive spectroscopic technique, precluding portable applications with small sample volumes, such as needed for biomarker detection in body fluids. Here we report a compact double resonant chip stack system that implements in situ dynamic nuclear polarisation of a 130 nL sample volume, achieving signal enhancements of up to - 60 w.r.t. the thermal equilibrium level at a microwave power level of 0.5 W. This work overcomes instrumental barriers to the use of NMR detection for point-of-care applications.
Collapse
|
5
|
Bogaychuk A, Kuzmin V. Accounting for material imperfections in the design and optimization of low cost Halbach magnets. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:103904. [PMID: 33138559 DOI: 10.1063/5.0013274] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Accepted: 10/06/2020] [Indexed: 06/11/2023]
Abstract
We demonstrate an experimental method for the improvement of the magnetic field homogeneity in Halbach magnets by taking magnet material imperfection into account. This method relies on the determination of the magnetization magnitude only for individual magnet blocks based on nuclear magnetic resonance field measurements in a simplified system, which, in our case, consists of four blocks. Then, a set of configurations with highest homogeneities can be found from simplified field map simulations of all possible configurations or by applying sophisticated optimum search algorithms if the number of blocks is large. Finally, the residual effect of angular magnetization deviations can be reduced by the experimental selection of the best configuration from the set found on the simulation step. This selection strategy is based on the conclusions made from statistical analysis of simulated field maps. By applying the described method to our eight-element magnet, we experimentally achieved tenfold field homogeneity improvement. Thus, in the best configuration, we obtained an average value of the magnetic field of 598.0 mT and a half-width of 226.9 ppm for a sample with a diameter of 4 mm and a height of 10 mm. These parameters along with the compact magnet size (40 × 40 × 102 mm3) and weight (0.6 kg) provide reasonable magnet quality compared with analogous systems having more complex magnet arrangements and significantly higher costs.
Collapse
Affiliation(s)
- A Bogaychuk
- Institute of Physics, Kazan Federal University, Kremlyovskaya Str. 18, Kazan 420008, Russia
| | - V Kuzmin
- Institute of Physics, Kazan Federal University, Kremlyovskaya Str. 18, Kazan 420008, Russia
| |
Collapse
|
6
|
Blümich B. Low-field and benchtop NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 306:27-35. [PMID: 31311709 DOI: 10.1016/j.jmr.2019.07.030] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 04/03/2019] [Accepted: 07/08/2019] [Indexed: 05/28/2023]
Abstract
NMR started at low field. Important discoveries like the first observation of NMR in condensed matter, the spin echo, NMR for chemical analysis, Fourier NMR spectroscopy, 2D NMR spectroscopy and magnetic resonance imaging happened at field strengths considered low today. With time the footprint of the NMR instruments at these field strengths shrunk from the laboratory floor to the tabletop. The first commercial tabletop NMR instruments were compact relaxometers for food analysis followed by mobile relaxometers for materials testing and oil-well exploration culminating in tabletop spectrometers for chemical analysis, capable of performing nearly the whole methodical portfolio of today's high-field instruments. The increasing sensitivity afforded by the lower noise of modern electronics and the unfolding richness of hyperpolarization scenarios along with detection schemes alternative to nuclear induction enable NMR at ultra-low field strengths down to zero applied field, where spin-spin couplings in local fields dominate the residual Zeeman interaction. Miniaturization and cost-reduction of NMR instruments outline current development goals along with the development of smart-phone-like apps to conduct standard NMR analyses.
Collapse
Affiliation(s)
- Bernhard Blümich
- Institut für Technische und Makromolekulare Chemie, RWTH Aachen University, Aachen, Germany.
| |
Collapse
|
7
|
Marques JP, Simonis FF, Webb AG. Low-field MRI: An MR physics perspective. J Magn Reson Imaging 2019; 49:1528-1542. [PMID: 30637943 PMCID: PMC6590434 DOI: 10.1002/jmri.26637] [Citation(s) in RCA: 161] [Impact Index Per Article: 32.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Revised: 11/28/2018] [Accepted: 11/28/2018] [Indexed: 01/21/2023] Open
Abstract
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.
Collapse
Affiliation(s)
- José P. Marques
- Radboud University, Donders Institute for Brain, Cognition and BehaviourNijmegenThe Netherlands
| | - Frank F.J. Simonis
- Magnetic Detection & Imaging, Technical Medical CentreUniversity of TwenteThe Netherlands
| | - Andrew G. Webb
- C.J.Gorter Center for High Field MRI, Department of RadiologyLeiden University Medical CentreThe Netherlands
| |
Collapse
|
8
|
Überrück T, Blümich B. Variable magnet arrays to passively shim compact permanent-yoke magnets. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 298:77-84. [PMID: 30529894 DOI: 10.1016/j.jmr.2018.11.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 11/14/2018] [Accepted: 11/27/2018] [Indexed: 05/03/2023]
Abstract
C-shaped permanent magnets offer a compromise between sample accessability and field strength as well as homogeneity compared to single-sided devices or Halbach arrays. A new approach to passively shim C-shaped dipole magnets is presented. It relies on the magnet poles being constructed from a set of adjustable magnet elements. Two pole concepts are introduced, which allow the correction of the field profile and passively shim the magnet without the need of additional pole shoes or shim pieces.
Collapse
Affiliation(s)
- Till Überrück
- RWTH Aachen University, Institut für Technische und Makromolekulare Chemie, Worringerweg 2, 52074 Aachen, Germany
| | - Bernhard Blümich
- RWTH Aachen University, Institut für Technische und Makromolekulare Chemie, Worringerweg 2, 52074 Aachen, Germany.
| |
Collapse
|
9
|
Blümich B, Rehorn C, Zia W. Magnets for Small-Scale and Portable NMR. MICRO AND NANO SCALE NMR 2018. [DOI: 10.1002/9783527697281.ch1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Bernhard Blümich
- RWTH Aachen University, Institut für Technische und Makromolekulare Chemie; Worringerweg 2 52074 Aachen Germany
| | - Christian Rehorn
- RWTH Aachen University, Institut für Technische und Makromolekulare Chemie; Worringerweg 2 52074 Aachen Germany
| | - Wasif Zia
- Sir Peter Mansfield Imaging Center, University of Nottingham; United Kingdom
| |
Collapse
|
10
|
Abe M. Passive Shimming of MRI Static Magnetic Field Using Regularization of Truncated Singular Value Decomposition. Magn Reson Med Sci 2017; 16:284-296. [PMID: 28250355 PMCID: PMC5743519 DOI: 10.2463/mrms.mp.2016-0046] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Accepted: 10/26/2016] [Indexed: 11/25/2022] Open
Abstract
PURPOSE To develop a new shimming calculation method, which can calculate iron piece placements rapidly to make the magnetic field homogeneous at intended homogeneity and then to make the shimming working time short. MATERIALS AND METHODS The shimming calculation yields magnetic moment (MM) distribution, which is calculated by the truncated singular value decomposition (SVD) from the measured magnetic field. The MM distribution is described by a superposition of eigenmodes obtained by SVD of a response matrix from the moment distributions to magnetic fields at the field of view (FOV). The homogeneity is regulated by a truncation number of the superposed eigenmodes. The magnetic moments are converted into iron volumes with the assumption of saturated magnetization and the iron pieces are placed according to the calculation results. Since the SVD calculation can be done in advance, the computational time at the shimming site is short. RESULTS Trial applications on a 0.5T magnetic resonance imaging (MRI) magnet were done using the new shimming calculation method, which was proved to work well. However, since the iron piece volumes had tolerances, the work was repeated until enough homogeneity was obtained. As a result, an intended homogeneity of 8.9 ppm (peak-to-peak) on 40 cm diameter spherical surface was successfully obtained from measured homogeneity of 543 ppm with short computational and working time. CONCLUSION The test shimming work showed that the developed shimming calculation method with truncated SVD regularization is applicable to the shimming work on the MRI magnets.
Collapse
Affiliation(s)
- Mitsushi Abe
- Hitachi, Ltd., Research & Development Group, Center of Technology Innovation–Energy, 7-2-1 Omika-cho, Hitachi, Ibaraki 319-1221, Japan
| |
Collapse
|
11
|
Mitchell J, Fordham EJ. Contributed review: nuclear magnetic resonance core analysis at 0.3 T. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:111502. [PMID: 25430091 DOI: 10.1063/1.4902093] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
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.
Collapse
Affiliation(s)
- Jonathan Mitchell
- Schlumberger Gould Research, High Cross, Madingley Road, Cambridge CB3 0EL, United Kingdom
| | - Edmund J Fordham
- Schlumberger Gould Research, High Cross, Madingley Road, Cambridge CB3 0EL, United Kingdom
| |
Collapse
|
12
|
Terada Y, Kono S, Uchiumi T, Kose K, Miyagi R, Yamabe E, Fujinaga Y, Yoshioka H. Improved reliability in skeletal age assessment using a pediatric hand MR scanner with a 0.3T permanent magnet. Magn Reson Med Sci 2014; 13:215-9. [PMID: 24990466 DOI: 10.2463/mrms.2013-0098] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
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 κ 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 κ 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.
Collapse
|
13
|
Zalesskiy SS, Danieli E, Blümich B, Ananikov VP. Miniaturization of NMR systems: desktop spectrometers, microcoil spectroscopy, and "NMR on a chip" for chemistry, biochemistry, and industry. Chem Rev 2014; 114:5641-94. [PMID: 24779750 DOI: 10.1021/cr400063g] [Citation(s) in RCA: 129] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Sergey S Zalesskiy
- Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences , Moscow, 119991, Russia
| | | | | | | |
Collapse
|