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Sherman SE, Zammit AS, Heo WS, Rosen MS, Cima MJ. Single-sided magnetic resonance-based sensor for point-of-care evaluation of muscle. Nat Commun 2024; 15:440. [PMID: 38199994 PMCID: PMC10782019 DOI: 10.1038/s41467-023-44561-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Accepted: 12/19/2023] [Indexed: 01/12/2024] Open
Abstract
Magnetic resonance imaging is a widespread clinical tool for the detection of soft tissue morphology and pathology. However, the clinical deployment of magnetic resonance imaging scanners is ultimately limited by size, cost, and space constraints. Here, we discuss the design and performance of a low-field single-sided magnetic resonance sensor intended for point-of-care evaluation of skeletal muscle in vivo. The 11 kg sensor has a penetration depth of >8 mm, which allows for an accurate analysis of muscle tissue and can avoid signal from more proximal layers, including subcutaneous adipose tissue. Low operational power and shielding requirements are achieved through the design of a permanent magnet array and surface transceiver coil. The sensor can acquire high signal-to-noise measurements in minutes, making it practical as a point-of-care tool for many quantitative diagnostic measurements, including T2 relaxometry. In this work, we present the in vitro and human in vivo performance of the device for muscle tissue evaluation.
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Affiliation(s)
- Sydney E Sherman
- Harvard-MIT Program in Health Science and Technology, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Alexa S Zammit
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Won-Seok Heo
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Matthew S Rosen
- Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, 02129, USA
- Harvard Medical School, Boston, MA, 02115, USA
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA
| | - Michael J Cima
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
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2
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Morin DM, Richard S, Ansaribaranghar N, Newling B, Balcom BJ. A low-field ceramic magnet design for magnetic resonance. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2024; 358:107599. [PMID: 38041994 DOI: 10.1016/j.jmr.2023.107599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 11/20/2023] [Accepted: 11/22/2023] [Indexed: 12/04/2023]
Abstract
We describe the design of a low-field portable magnet, based on two ceramic magnets, separated by a distance, with their magnetic poles aligned to create a large homogeneous region with a field strength of 425 gauss. Ceramic magnets are an uncommon choice compared to Neodymium Iron Boron magnets for low-field magnetic resonance but are preferable for our purposes to create a homogeneous region at lower field strength. The low cost of large ceramic magnets results in an inexpensive design with a large measurement volume. The magnets rest in a 3D-printed structure, which allows for the magnets to be moved by hand so the experimentalist has control over the field topology. To test the utility of the design, we explored an Overhauser dynamic nuclear polarization experiment with an aqueous solution of 4-Hydroxy-TEMPO. We also explored a simple flow measurement employing the ceramic magnets at a 6-degree pitch, creating a 14.6 gauss/cm constant gradient.
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Affiliation(s)
- Devin M Morin
- UNB MRI Centre, Department of Physics, University of New Brunswick, Fredericton E3B 5A3, Canada
| | - Sebastian Richard
- UNB MRI Centre, Department of Physics, University of New Brunswick, Fredericton E3B 5A3, Canada
| | - Naser Ansaribaranghar
- UNB MRI Centre, Department of Physics, University of New Brunswick, Fredericton E3B 5A3, Canada
| | - Benedict Newling
- UNB MRI Centre, Department of Physics, University of New Brunswick, Fredericton E3B 5A3, Canada
| | - Bruce J Balcom
- UNB MRI Centre, Department of Physics, University of New Brunswick, Fredericton E3B 5A3, Canada.
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3
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He J, Kong X, Xu Z. Improving the SNR of UMR sensor using LC resonator. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 356:107580. [PMID: 37924681 DOI: 10.1016/j.jmr.2023.107580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2023] [Revised: 10/23/2023] [Accepted: 10/26/2023] [Indexed: 11/06/2023]
Abstract
Single-sided or unilateral magnetic resonance (UMR) technology has various benefits, such as an open structure, low cost, portability, and nondestructive measurement, in contrast to the conventional closed magnet structure. UMR is widely used in material analysis, well logging, and biomedicine. However, its development is constrained by its poor signal-to-noise ratio (SNR). To enhance the SNR of UMR sensor, a surface coil of LC resonator is added on the Radio Frequency (RF) coil. First, a method of calculating the current in the RF coil including LC resonator is derived. Next, the equivalent AC resistance of the coil is calculated using the partial-element equivalent-circuit (PEEC) method. Finally, the SNR of a UMR sensor incorporating LC resonator is analyzed, and its sensitivity map is provided. Experimental comparisons are made between the UMR sensor with and without a LC resonator. Results show that the SNR of the UMR can be enhanced by up to three times after the LC resonator is loaded. The SNR improves within 30 mm of the coil surface, and this beneficial effect steadily diminishes as the distance increases. This study offers a useful method for improving the signal of UMR sensors.
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Affiliation(s)
- Jiali He
- School of Electrical Engineering, Chongqing University, Chongqing, China
| | - Xiaohan Kong
- Graduate School of Information Science and Technology, Hokkaido University, Sapporo 060-0814, Japan
| | - Zheng Xu
- School of Electrical Engineering, Chongqing University, Chongqing, China.
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4
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Cima M, Sherman S, Zammit A, Heo WS, Rosen M. Single-sided magnetic resonance-based sensor for point-of-care evaluation of muscle. RESEARCH SQUARE 2023:rs.3.rs-3335248. [PMID: 37790511 PMCID: PMC10543496 DOI: 10.21203/rs.3.rs-3335248/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/05/2023]
Abstract
Magnetic resonance (MR) imaging is a powerful clinical tool for the detection of soft tissue morphology and pathology, which often provides actionable diagnostic information to clinicians. Its clinical use is largely limited due to size, cost, time, and space constraints. Here, we discuss the design and performance of a low-field single-sided MR sensor intended for point-of-care (POC) evaluation of skeletal muscle in vivo. The 11kg sensor has a penetration depth of > 8 mm, which allows for an accurate analysis of muscle tissue and can avoid signal from more proximal layers, including subcutaneous adipose tissue. Low operational power and minimal shielding requirements are achieved through the design of a permanent magnet array and surface transceiver coil. We present the in vitro and human in vivo performance of the device for muscle tissue evaluation. The sensor can acquire high signal-to-noise (SNR > 150) measurements in minutes, making it practical as a POC tool for many quantitative diagnostic measurements, including T2 relaxometry.
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Affiliation(s)
| | | | | | | | - Matthew Rosen
- Massachusetts General Hospital and Harvard Medical School
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5
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Morin DM, Lawrence M, Balcom BJ. Design and validation of a single-sided magnet with a constant gradient parallel to its surface. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2022; 342:107266. [PMID: 35905531 DOI: 10.1016/j.jmr.2022.107266] [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: 02/09/2022] [Revised: 06/15/2022] [Accepted: 07/04/2022] [Indexed: 06/15/2023]
Abstract
We present the design, validation, and testing of an optimized 5 MHz three-magnet array with a gradient parallel to the magnet surface. An approach to permanent magnet array design is explored with a genetic algorithm. The genetic algorithm was used to produce multiple designs based on an inventory of available block magnets. One three-magnet array was constructed for testing. Constant gradients of 205, 115, and 61 gauss/cm, parallel to the magnet surface are found at displacements of 1.5, 2.0, and 2.5 cm from the surface of the magnet, respectively. Regions of useful gradient are roughly 1 cm in length. We constructed and field plotted the three-magnet array and found good agreement between the experimental and simulated magnet fields. To test applicability, we performed T1 and T2 relaxation measurements on a cod liver oil sample, and a simple doped water flow measurement.
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Affiliation(s)
- Devin M Morin
- UNB MRI Centre, Department of Physics, University of New Brunswick, Fredericton E3B 5A3, Canada
| | - Maggie Lawrence
- UNB MRI Centre, Department of Physics, University of New Brunswick, Fredericton E3B 5A3, Canada
| | - Bruce J Balcom
- UNB MRI Centre, Department of Physics, University of New Brunswick, Fredericton E3B 5A3, Canada.
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6
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Gruber DM, Fricke SN, Lee V, Balcom BJ, Augustine MP. Coils for large standoff relaxometry with unilateral magnets. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2022; 342:107271. [PMID: 35963026 DOI: 10.1016/j.jmr.2022.107271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2021] [Revised: 06/28/2022] [Accepted: 07/14/2022] [Indexed: 06/15/2023]
Abstract
Maximizing standoff distance by direct placement of probe coils on magnet bodies, while maximizing signal-to-noise is critical to the successful application of unilateral NMR. Two types of radio frequency (rf) coils for linear array, unilateral magnets are described: "simple fringe" and "split fringe coils." These coils are designed to fully exploit the standoff distance of the unilateral magnet by placement directly on the magnet surface. Such placement fails for normal surface coils used for magnetic resonance due to eddy current induced shielding by the conductive magnet surface. The coil design strategy includes a rectangular cross section solenoid coil, either continuous or split in the center, mounted with the center axis of the coil parallel to the magnet surface. These geometries, when placed on a conducting surface, enhance the rf field produced in the sample region, outside of the solenoid coil. The spatial homogeneity of both rf coils are characterized using the ANSYS™ finite element modelling software. ANSYS™ modeled coil geometries led to homogeneous, surface displaced rf fields. These coils were then constructed and characterized with magnetic resonance imaging. Finally, two experiments that use these coils to perform large standoff relaxation measurements are described.
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Affiliation(s)
- Daniel M Gruber
- Department of Chemistry, 69 Chemistry Building, University of California, Davis, Davis, CA 95616, USA
| | - Sophia N Fricke
- Department of Chemistry, 69 Chemistry Building, University of California, Davis, Davis, CA 95616, USA
| | - Vanessa Lee
- Department of Chemistry, 69 Chemistry Building, University of California, Davis, Davis, CA 95616, USA
| | - Bruce J Balcom
- Department of Physics, UNB MRI Centre, University of New Brunswick, Fredericton, New Brunswick, Canada
| | - Matthew P Augustine
- Department of Chemistry, 69 Chemistry Building, University of California, Davis, Davis, CA 95616, USA.
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7
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Tewari S, Yousefi S, Webb A. Deep neural-network based optimization for the design of a multi-element surface magnet for MRI applications. INVERSE PROBLEMS 2022; 38:035003. [PMID: 36046464 PMCID: PMC7613466 DOI: 10.1088/1361-6420/ac492a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
We present a combination of a CNN-based encoder with an analytical forward map for solving inverse problems. We call it an encoder-analytic (EA) hybrid model. It does not require a dedicated training dataset and can train itself from the connected forward map in a direct learning fashion. A separate regularization term is not required either, since the forward map also acts as a regularizer. As it is not a generalization model it does not suffer from overfitting. We further show that the model can be customized to either find a specific target solution or one that follows a given heuristic. As an example, we apply this approach to the design of a multi-element surface magnet for low-field magnetic resonance imaging (MRI). We further show that the EA model can outperform the benchmark genetic algorithm model currently used for magnet design in MRI, obtaining almost 10 times better results.
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Affiliation(s)
- Sumit Tewari
- C.J. Gorter Center for High Field MRI, Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Sahar Yousefi
- Division of Image Processing, Leiden University Medical Center, Leiden, The Netherlands
| | - Andrew Webb
- C.J. Gorter Center for High Field MRI, Radiology, Leiden University Medical Center, Leiden, The Netherlands
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8
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Utsuzawa S, Tang Y, Song YQ. Inside-out NMR with two concentric ring magnets. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2021; 333:107082. [PMID: 34688178 DOI: 10.1016/j.jmr.2021.107082] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2021] [Revised: 09/29/2021] [Accepted: 09/30/2021] [Indexed: 06/13/2023]
Abstract
We report the design and the implementation of an inside-out NMR sensor that produces a large sensitive region with substantially uniform magnetic field at a remote location. The construction using a pair of ring magnets is simple yet provides multiple benefits, including large sample volume, operation with low RF power, and the ability to measure samples with long T2 and high diffusivity. A palm-size inside-out NMR sensor (57 mm OD × 29 mm height, 420 g including the housing and the coil PCB) was built with inexpensive magnets. The sweet spot is located ∼5 mm above the magnet surface with ∼4 mm width and ∼5 mm height assuming t180 = 18 μs. The field strength at that point is 0.16 T and achieved SNR ∼23 per two scans when operated with ∼10 W peak RF power. Its quasi-uniform B0 around the saddle point allows the measurement of T2 = 1.5 s with a 100 μs echo time.
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Affiliation(s)
- Shin Utsuzawa
- Schlumberger-Doll Research, Cambridge, MA 02139, USA.
| | - Yiqiao Tang
- Schlumberger-Doll Research, Cambridge, MA 02139, USA
| | - Yi-Qiao Song
- Schlumberger-Doll Research, Cambridge, MA 02139, USA; Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA; John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
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9
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Grandinetti J, Zhong Y, Shen C, Jia X. Design and experimental validation of a unilateral magnet for MRI-guided small animal radiation experiments. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2021; 332:107062. [PMID: 34601187 PMCID: PMC8546776 DOI: 10.1016/j.jmr.2021.107062] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 08/05/2021] [Accepted: 08/20/2021] [Indexed: 06/13/2023]
Abstract
Small animal radiation experiments are of paramount importance for the advancement of human radiation therapy. These experiments use a dedicated radiation platform to deliver radiation to small animals, such as mice and rats, similar to how human radiation therapy is performed. By acquiring images immediately before radiation delivery to guide positioning of the animals, image guidance plays a critical role to ensure accuracy of the experiments. Recently, MR-based image guidance has been enabled in human radiation therapy. This paper proposes a new concept using a unilateral magnet-based MRI scanner to realize image guidance for small animal radiation experiments. We reported our design, optimization, construction, and characterization of the magnet. The magnet was designed using eight 2-inch neodymium magnet cubes arranged in a modified Halbach ring configuration. The ring has an opening to allow for animal positioning. We considered a spherical region of interest (ROI) located outside of the ring's plane to allow radiation delivery to the ROI without obstruction of the magnet. An optimization problem was formulated and solved to determine the positions and orientations of the magnet cubes to generate a magnetic field with desired properties in the ROI. The optimization improved the average magnetic flux density from 55 mT to 72 mT and reduced variation from 1.2 T/m to 1.0 T/m. We constructed the magnet using 3D-printed templates to hold the neodymium magnet cubes with the optimized positions and orientations. We measured the spatial distribution of the magnetic flux density. The measurement results and computed results agreed with an average difference of 0.35% through the ROI.
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Affiliation(s)
- Jace Grandinetti
- innovative Technology Of Radiotherapy Computations and Hardware (iTORCH) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas 75390, TX, USA
| | - Yuncheng Zhong
- innovative Technology Of Radiotherapy Computations and Hardware (iTORCH) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas 75390, TX, USA
| | - Chenyang Shen
- innovative Technology Of Radiotherapy Computations and Hardware (iTORCH) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas 75390, TX, USA.
| | - Xun Jia
- innovative Technology Of Radiotherapy Computations and Hardware (iTORCH) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas 75390, TX, USA.
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10
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Wang Y, Xu Y, Zhang M, Emmanuel Komolafe T, Wang W, Luo H, Chen X, Yang X, Wu Z. A single-sided magnet for deep-depth fat quantification. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2021; 331:107053. [PMID: 34428727 DOI: 10.1016/j.jmr.2021.107053] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 06/06/2021] [Accepted: 08/05/2021] [Indexed: 06/13/2023]
Abstract
Early detection of fatty-liver disease is important before further aggravations of the disease, such as cirrhosis, can develop. In this study, we developed a low-cost, movable single-sided magnet for in vivo liver fat quantification. A gradient field of 73.5 G/cm and a field strength of 0.0725 T were obtained by structurally optimizing the concave U-shaped magnet, on which the region of interest (ROI) was a curved shape about 0.4 mm thick, 8 cm above the surface of the radiofrequency (RF) coil. We constructed a prototype nuclear magnetic-resonance (NMR) relaxometry system based on this optimized magnet. Subsequent phantom experiments demonstrated the effectiveness of the single-sided magnet in evaluating different proton density fat fraction (PDFF) phantoms. As expected, the results of the six phantoms showed good positive correlation between PDFF and the fitted fat amplitude, which suggested that single-sided NMR relaxometry could be used to quantify liver fat in vivo.
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Affiliation(s)
- Ya Wang
- Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, Jiangsu, China; School of Biomedical Engineering (Suzhou), Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230026, China
| | - Yajie Xu
- Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, Jiangsu, China
| | - Mingkang Zhang
- Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, Jiangsu, China; School of Electronic and Information Engineering, Changchun University of Science and Technology, 130022, Changchun, China
| | - Temitope Emmanuel Komolafe
- Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, Jiangsu, China; School of Biomedical Engineering (Suzhou), Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230026, China
| | - Weiqian Wang
- Wuxi Marvel Stone Healthcare Co. Ltd., Wuxi 214135, Jiangsu, China
| | - Hai Luo
- Wuxi Marvel Stone Healthcare Co. Ltd., Wuxi 214135, Jiangsu, China
| | - Xiao Chen
- Wuxi Marvel Stone Healthcare Co. Ltd., Wuxi 214135, Jiangsu, China
| | - Xiaodong Yang
- Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, Jiangsu, China.
| | - Ziyue Wu
- Wuxi Marvel Stone Healthcare Co. Ltd., Wuxi 214135, Jiangsu, China.
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11
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Silva P, Jouda M, Korvink J. Magnetostatic reciprocity for MR magnet design. MAGNETIC RESONANCE (GOTTINGEN, GERMANY) 2021; 2:607-617. [PMID: 37905211 PMCID: PMC10539805 DOI: 10.5194/mr-2-607-2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Accepted: 06/29/2021] [Indexed: 11/02/2023]
Abstract
Electromagnetic reciprocity has long been a staple in magnetic resonance (MR) radio-frequency development, offering geometrical insights and a figure of merit for various resonator designs. In a similar manner, we use magnetostatic reciprocity to compute manufacturable solutions of complex magnet geometries, by establishing a quantitative metric for the placement and subsequent orientation of discrete pieces of permanent magnetic material. Based on magnetostatic theory and non-linear finite element modelling (FEM) simulations, it is shown how assembled permanent magnet setups perform in the embodiment of a variety of designs and how magnetostatic reciprocity is leveraged in the presence of difficulties associated with self-interactions, to fulfil various design objectives, including self-assembled micro-magnets, adjustable magnetic arrays, and an unbounded magnetic field intensity in a small volume, despite realistic saturation field strengths.
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Affiliation(s)
- Pedro Freire Silva
- Karlsruhe Institute of Technology (KIT), Institute of Microstructure Technology, 76131 Karlsruhe, Germany
| | - Mazin Jouda
- Karlsruhe Institute of Technology (KIT), Institute of Microstructure Technology, 76131 Karlsruhe, Germany
| | - Jan G. Korvink
- Karlsruhe Institute of Technology (KIT), Institute of Microstructure Technology, 76131 Karlsruhe, Germany
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12
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Barbieri M, Fantazzini P, Testa C, Bortolotti V, Baruffaldi F, Kogan F, Brizi L. Characterization of Structural Bone Properties through Portable Single-Sided NMR Devices: State of the Art and Future Perspectives. Int J Mol Sci 2021; 22:7318. [PMID: 34298936 PMCID: PMC8303251 DOI: 10.3390/ijms22147318] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 06/30/2021] [Accepted: 07/02/2021] [Indexed: 11/18/2022] Open
Abstract
Nuclear Magnetic Resonance (NMR) is a well-suited methodology to study bone composition and structural properties. This is because the NMR parameters, such as the T2 relaxation time, are sensitive to the chemical and physical environment of the 1H nuclei. Although magnetic resonance imaging (MRI) allows bone structure assessment in vivo, its cost limits the suitability of conventional MRI for routine bone screening. With difficulty accessing clinically suitable exams, the diagnosis of bone diseases, such as osteoporosis, and the associated fracture risk estimation is based on the assessment of bone mineral density (BMD), obtained by the dual-energy X-ray absorptiometry (DXA). However, integrating the information about the structure of the bone with the bone mineral density has been shown to improve fracture risk estimation related to osteoporosis. Portable NMR, based on low-field single-sided NMR devices, is a promising and appealing approach to assess NMR properties of biological tissues with the aim of medical applications. Since these scanners detect the signal from a sensitive volume external to the magnet, they can be used to perform NMR measurement without the need to fit a sample inside a bore of a magnet, allowing, in principle, in vivo application. Techniques based on NMR single-sided devices have the potential to provide a high impact on the clinical routine because of low purchasing and running costs and low maintenance of such scanners. In this review, the development of new methodologies to investigate structural properties of trabecular bone exploiting single-sided NMR devices is reviewed, and current limitations and future perspectives are discussed.
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Affiliation(s)
- Marco Barbieri
- Department of Radiology, Stanford University, Stanford, CA 94395, USA;
- Department of Physics and Astronomy “Augusto Righi”, University of Bologna, 40127 Bologna, Italy; (P.F.); (C.T.)
| | - Paola Fantazzini
- Department of Physics and Astronomy “Augusto Righi”, University of Bologna, 40127 Bologna, Italy; (P.F.); (C.T.)
| | - Claudia Testa
- Department of Physics and Astronomy “Augusto Righi”, University of Bologna, 40127 Bologna, Italy; (P.F.); (C.T.)
- IRCCS Istituto delle Scienze Neurologiche Bologna, Functional and Molecular Neuroimaging Unit, 40139 Bologna, Italy
| | - Villiam Bortolotti
- Department of Civil, Chemical, Environmental, and Materials Engineering, University of Bologna, 40134 Bologna, Italy;
| | - Fabio Baruffaldi
- Medical Technology Laboratory, IRCCS Istituto Ortopedico Rizzoli, 40136 Bologna, Italy;
| | - Feliks Kogan
- Department of Radiology, Stanford University, Stanford, CA 94395, USA;
| | - Leonardo Brizi
- Department of Physics and Astronomy “Augusto Righi”, University of Bologna, 40127 Bologna, Italy; (P.F.); (C.T.)
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13
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Ross MMB, Wilbur GR, Cano Barrita PFDJ, Balcom BJ. A portable, submersible, MR sensor - The Proteus magnet. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2021; 326:106964. [PMID: 33773442 DOI: 10.1016/j.jmr.2021.106964] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 03/04/2021] [Accepted: 03/07/2021] [Indexed: 06/12/2023]
Abstract
This paper details the design, fabrication, and testing of a new portable magnet, generically termed the Proteus magnet, that can undertake a wide range of MR measurements. The Proteus magnet is intended for 1H measurements of liquids and is fully functional when submersed in the sample of interest. The Proteus magnet is fabricated from a pair of low-cost, commercial, NdFeB disk magnets, axially polarized, with their North and South poles aligned. The two N52 NdFeB magnets - 31.75 mm diameter and 6.35 mm thickness were separated by 10 mm. The gap between the magnets is sufficient for a RF shield and transverse rectangular solenoid RF probe. The sensor was evaluated through a series of measurements including bulk CPMG, saturation recovery T1, self-diffusion, T1 - T2, and D - T2.
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Affiliation(s)
- Michael M B Ross
- UNB MRI Centre, Department of Physics, University of New Brunswick, Fredericton, New Brunswick E3B 5A3, Canada.
| | - Grant R Wilbur
- UNB MRI Centre, Department of Physics, University of New Brunswick, Fredericton, New Brunswick E3B 5A3, Canada.
| | | | - Bruce J Balcom
- UNB MRI Centre, Department of Physics, University of New Brunswick, Fredericton, New Brunswick E3B 5A3, Canada.
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14
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Nakashima Y, Shiba N. Nondestructive measurement of intramuscular fat content of fresh beef meat by a hand-held magnetic resonance sensor. INTERNATIONAL JOURNAL OF FOOD PROPERTIES 2021. [DOI: 10.1080/10942912.2021.1999261] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Yoshito Nakashima
- Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
| | - Nobuya Shiba
- Livestock and Forage Research Division, National Agriculture and Food Research Organization (NARO), Tohoku Agricultural Research Center, Morioka, Japan
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15
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Wilbur G, MacMillan B, Bade KM, Mastikhin I. MRI monitoring of sea spray freezing. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 310:106647. [PMID: 31760148 DOI: 10.1016/j.jmr.2019.106647] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 11/10/2019] [Accepted: 11/11/2019] [Indexed: 06/10/2023]
Abstract
Sea spray icing is a common hazard for vessels and offshore structures in cold climates. In this paper, quantitative 3D MRI and T1 - T2 mapping of the formation of sea spray ice were performed. Three different freezing regimes were employed. During freezing, changes in both relaxation times and signal intensity were greater than an order of magnitude. Results show strong differences in brine intensity and distribution for the three freezing regimes. The observed ranges of spin densities and relaxation times during freezing are well suited to measurements with portable NMR devices. There is a considerable potential for the use of MRI in studies of sea spray ice.
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Affiliation(s)
- Grant Wilbur
- MRI Centre, Department of Physics, UNB, Fredericton, NB, Canada
| | - Bryce MacMillan
- MRI Centre, Department of Physics, UNB, Fredericton, NB, Canada
| | - Kyle M Bade
- Spraying Systems Co., Spray Analysis and Research Services, Wheaton, IL, USA
| | - Igor Mastikhin
- MRI Centre, Department of Physics, UNB, Fredericton, NB, Canada.
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16
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Shen S, Guo P, Wu J, Ding Y, Chen F, Meng F, Xu Z. Optimized inside-out magnetic resonance probe for soil moisture measuring in situ. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 307:106565. [PMID: 31404875 DOI: 10.1016/j.jmr.2019.07.052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 07/23/2019] [Accepted: 07/24/2019] [Indexed: 06/10/2023]
Abstract
We report a novel inside-out NMR (nuclear magnetic resonance) probe for the measurement of soil moisture. The probe consists of a dumbbell-shape magnet and an opposed-solenoid RF (radio frequency) coil. Optimization methods for the structure of the magnet and RF coil that maximize the SNR (signal-to-noise ratio) of NMR measurements are also described. The dumbbell-shape magnet consists of three cylindrical magnets in series whose magnetic field was calculated with analytic expression deduced by converting magnet to equivalent magnetization current on its cylindrical surface. Based on the analytic expression, a nonlinear optimization mathematical model was built to determine the optimal structure parameters automatically. The opposed-solenoid is a pair of reverse-connected solenoids and used as RF coil on inside-out NMR probe in this work. Its structure-parameter optimization was carried out based on FEM (finite element method) simulation, and UD (uniform design) was applied to increase the optimization efficiency. A prototype was designed and built consisting of a magnet with length of 100 mm and a diameter of 40 mm. An NMR-based soil moisture measuring experiment was conducted by this prototype, with NMR performed using the CPMG (Carr-Purcell-Meiboom-Gill) pulse sequence for soil sample in different moisture content. The T2 distribution spectrum reveals that there are two compartments of water in the soil sample: free water and bound water.
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Affiliation(s)
- Sheng Shen
- State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044, China
| | - Pan Guo
- School of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331, China
| | - Jiamin Wu
- State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044, China
| | - Ye Ding
- State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044, China
| | - Fangge Chen
- State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044, China
| | - Fanqin Meng
- State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044, China
| | - Zheng Xu
- State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044, China.
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17
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Martin MN, Balcom BJ, McCarthy MJ, Augustine MP. Noninvasive, Nondestructive Measurement of Tomato Concentrate Spoilage in Large-Volume Aseptic Packages. J Food Sci 2019; 84:2898-2906. [PMID: 31538343 DOI: 10.1111/1750-3841.14778] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 07/19/2019] [Accepted: 07/22/2019] [Indexed: 11/28/2022]
Abstract
Low frequency nuclear magnetic resonance (NMR) is used to noninvasively and nondestructively detect spoiled tomato concentrate stored in >200 L metal-lined containers. It is shown that longitudinal and transverse NMR relaxation times change as the tomato concentrate spoils. A rapid, viscosity-dependent spoilage detection method that takes advantage of the inherent inhomogeneity in single-sided NMR instruments is proposed. Here, the effective transverse magnetization decay rate is used as a parameter to determine tomato concentrate spoilage. Three different low frequency, single-sided NMR instruments are described and compared to determine the optimum sensor for spoiled tomato concentrate detection in large-format, metal-lined, aseptic containers. The most effective NMR sensor for this application is temperature stable and has large magnetic field gradients and a homogeneous magnetic field region offset >0.5 cm from the magnet surface. PRACTICAL APPLICATION: This manuscript describes a noninvasive and nondestructive tomato concentrate spoilage detector for application to large-format, sealed, commercial storage bins.
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Affiliation(s)
- Michele N Martin
- Dept. of Chemistry, Univ. of California, Davis, One Shields Ave., Davis, CA, 95616, U.S.A
| | - Bruce J Balcom
- Dept. of Physics, Univ. of New Brunswick, Fredricton, New Brunswick, E3B 5A3, Canada
| | - Michael J McCarthy
- Dept. of Chemistry, Univ. of California, Davis, One Shields Ave., Davis, CA, 95616, U.S.A
| | - Matthew P Augustine
- Dept. of Chemistry, Univ. of California, Davis, One Shields Ave., Davis, CA, 95616, U.S.A
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18
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Kerr JD, Balcom BJ, McCarthy MJ, Augustine MP. A low cost, portable NMR probe for high pressure, MR relaxometry. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 304:35-41. [PMID: 31077930 DOI: 10.1016/j.jmr.2019.05.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 05/02/2019] [Accepted: 05/02/2019] [Indexed: 06/09/2023]
Abstract
A low cost, portable, high volume, stainless steel pressure reactor is modified to easily perform magnetic resonance relaxometry at industrially relevant pressures. Unlike existing pressurization strategies common to nuclear magnetic resonance (NMR) spectroscopy, this approach is amenable to realistic samples that feature heterogeneity and have traditionally escaped NMR study at pressure. This pressure reactor/NMR probe combination is easily accommodated by most single-sided and other low magnetic field permanent magnet assemblies. The performance of the probe is demonstrated by accomplishing NMR relaxometry on polydimethylsiloxane at different pressures with two types of unilateral magnets.
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Affiliation(s)
- Julia D Kerr
- Department of Chemistry, 69 Chemistry Building, University of California, Davis, Davis, CA 95616 USA
| | - Bruce J Balcom
- Department of Physics, UNB MRI Centre, University of New Brunswick, Fredericton, New Brunswick, Canada
| | - Michael J McCarthy
- Department of Chemistry, 69 Chemistry Building, University of California, Davis, Davis, CA 95616 USA
| | - Matthew P Augustine
- Department of Chemistry, 69 Chemistry Building, University of California, Davis, Davis, CA 95616 USA.
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19
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Mini Inside-Out Nuclear Magnetic Resonance Sensor Design for Soil Moisture Measurements. SENSORS 2019; 19:s19071682. [PMID: 30970536 PMCID: PMC6480103 DOI: 10.3390/s19071682] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 04/01/2019] [Accepted: 04/03/2019] [Indexed: 11/29/2022]
Abstract
The improvement of water management in agriculture by exactly detecting moisture parameters of soil is crucial. To investigate this problem, a mini inside-out nuclear magnetic resonance sensor (NMR) was proposed to measure moisture parameters of model soils. This sensor combines three cylindrical magnets that are magnetized in the axial direction and three arc spiral coils of the same size in series. We calculated and optimized the magnet structure by equivalent magnetization to current density. By adjusting the radius and height between the cylinders, a circumferential symmetric constant gradient field (2.28 T/m) was obtained. The NMR sensor was set at 2.424 MHz to measure the water content of sandy soil with small particle diameter and silica sand with large particle diameter. The complete decaying, an NMR signal was analyzed through inverse Laplace transformation and averaged on a T2 space. According to the results, moisture content of the sample is positively correlated with the integral area of T2 spectrum peak (Apeak); T2 of the water in small pores is shorter than that in large pores, because the movement of water molecules are limited by the inner wall of the pores. In the same volume, water in large pore sample is more than that in small pore sample, so Apeak of silica sand is larger than Apeak of sandy soil. Therefore, the sensor is capable of detecting moisture both content and pore size of the sample. This mini sensor (4.0 cm in diameter and 10 cm in length) is portable, and the lowest measurable humidity is 0.38%. Thus, this sensor will allow easy soil moisture measurements on-field in the future.
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20
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Nakashima Y. Non-Destructive Quantification of Lipid and Water in Fresh Tuna Meat by a Single-Sided Nuclear Magnetic Resonance Scanner. JOURNAL OF AQUATIC FOOD PRODUCT TECHNOLOGY 2019. [DOI: 10.1080/10498850.2019.1569742] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Yoshito Nakashima
- Research Institute for Geo-Resources and Environment, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan
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21
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Huber C, Goertler M, Abert C, Bruckner F, Groenefeld M, Teliban I, Suess D. Additive Manufactured and Topology Optimized Passive Shimming Elements for Permanent Magnetic Systems. Sci Rep 2018; 8:14651. [PMID: 30279477 PMCID: PMC6168460 DOI: 10.1038/s41598-018-33059-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 09/20/2018] [Indexed: 11/30/2022] Open
Abstract
A method to create a highly homogeneous magnetic field by applying topology optimized, additively manufactured passive shimming elements is investigated. The topology optimization algorithm can calculate a suitable permanent and nonlinear soft magnetic design that fulfills the desired field properties. The permanent magnetic particles are bonded in a polyamide matrix and they are manufactured with a low-cost, end-user 3D printer. Stray field measurements and an inverse stray field simulation framework can determine printing and magnetization errors. The customized shimming elements are manufactured by a selective melting process which produces completely dense soft magnetic metal parts. The methodology is demonstrated on a simple example of two axial symmetric cylindrical magnets, which generates a high inhomogeneous magnetic field. In this case, the maximum magnetic field density is 25 mT and the the homogeneity can be increased by a factor of 35 or down to 6‰. Simulation and measurement results point out a good conformity. Additional topology optimizations of more than one shimming element layer show the opportunity to make the manufactured magnetic system even more homogeneous.
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Affiliation(s)
- Christian Huber
- Physics of Functional Materials, University of Vienna, 1090, Vienna, Austria. .,Christian Doppler Laboratory for Advanced Magnetic Sensing and Materials, 1090, Vienna, Austria.
| | - Michael Goertler
- Institute for Surface Technologies and Photonics, Joanneum Research Forschungsgesellschaft GmbH, 8712, Niklasdorf, Austria
| | - Claas Abert
- Physics of Functional Materials, University of Vienna, 1090, Vienna, Austria.,Christian Doppler Laboratory for Advanced Magnetic Sensing and Materials, 1090, Vienna, Austria
| | - Florian Bruckner
- Physics of Functional Materials, University of Vienna, 1090, Vienna, Austria.,Christian Doppler Laboratory for Advanced Magnetic Sensing and Materials, 1090, Vienna, Austria
| | | | | | - Dieter Suess
- Physics of Functional Materials, University of Vienna, 1090, Vienna, Austria.,Christian Doppler Laboratory for Advanced Magnetic Sensing and Materials, 1090, Vienna, Austria
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22
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Bashyam A, Li M, Cima MJ. Design and experimental validation of Unilateral Linear Halbach magnet arrays for single-sided magnetic resonance. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 292:36-43. [PMID: 29763794 DOI: 10.1016/j.jmr.2018.05.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Revised: 05/07/2018] [Accepted: 05/08/2018] [Indexed: 06/08/2023]
Abstract
Single-sided NMR has the potential for broad utility and has found applications in healthcare, materials analysis, food quality assurance, and the oil and gas industry. These sensors require a remote, strong, uniform magnetic field to perform high sensitivity measurements. We demonstrate a new permanent magnet geometry, the Unilateral Linear Halbach, that combines design principles from "sweet-spot" and linear Halbach magnets to achieve this goal through more efficient use of magnetic flux. We perform sensitivity analysis using numerical simulations to produce a framework for Unilateral Linear Halbach design and assess tradeoffs between design parameters. Additionally, the use of hundreds of small, discrete magnets within the assembly allows for a tunable design, improved robustness to variability in magnetization strength, and increased safety during construction. Experimental validation using a prototype magnet shows close agreement with the simulated magnetic field. The Unilateral Linear Halbach magnet increases the sensitivity, portability, and versatility of single-sided NMR.
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Affiliation(s)
- Ashvin Bashyam
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, United States; Electrical Engineering & Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, United States.
| | - Matthew Li
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, United States; Harvard-MIT Program of Health Sciences and Technology, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, United States.
| | - Michael J Cima
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, United States; Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, United States.
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23
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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
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24
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Utsuzawa S, Fukushima E. Unilateral NMR with a barrel magnet. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2017; 282:104-113. [PMID: 28797924 DOI: 10.1016/j.jmr.2017.07.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2017] [Accepted: 07/17/2017] [Indexed: 06/07/2023]
Abstract
Unilateral NMR can examine samples without regard to sample size. It is also an easy path to mobile or portable NMR as well as inexpensive NMR. The objective of this work was to develop unilateral NMR with an improved performance in a sample region that was remote from the apparatus. This was accomplished with the creation of a saddle point where all second derivatives of the main component of the field were nulled. A ∼10cm diameter ∼5cm thick magnet combined with a gradiometer coil on the surface detected signals from a sensitive region that extended ∼2cm from the magnet. The relatively homogeneous field of these unilateral NMR devices allows the measurement of rapidly diffusing spins as well as the use of smaller RF amplifiers, which enhances system mobility.
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Affiliation(s)
- Shin Utsuzawa
- New Mexico Resonance, 2301 Yale Blvd SE, Suite C-1, Albuquerque, NM 87106, USA
| | - Eiichi Fukushima
- ABQMR, Inc., 2301 Yale Blvd SE, Suite C-2, Albuquerque, NM 87106, USA.
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25
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Wang Q, Gao R, Liu S. Topology optimization based design of unilateral NMR for generating a remote homogeneous field. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2017; 279:51-59. [PMID: 28463746 DOI: 10.1016/j.jmr.2017.04.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2016] [Revised: 04/07/2017] [Accepted: 04/07/2017] [Indexed: 06/07/2023]
Abstract
This paper presents a topology optimization based design method for the design of unilateral nuclear magnetic resonance (NMR), with which a remote homogeneous field can be obtained. The topology optimization is actualized by seeking out the optimal layout of ferromagnetic materials within a given design domain. The design objective is defined as generating a sensitive magnetic field with optimal homogeneity and maximal field strength within a required region of interest (ROI). The sensitivity of the objective function with respect to the design variables is derived and the method for solving the optimization problem is presented. A design example is provided to illustrate the utility of the design method, specifically the ability to improve the quality of the magnetic field over the required ROI by determining the optimal structural topology for the ferromagnetic poles. Both in simulations and experiments, the sensitive region of the magnetic field achieves about 2 times larger than that of the reference design, validating validates the feasibility of the design method.
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Affiliation(s)
- Qi Wang
- State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116024, China
| | - Renjing Gao
- State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116024, China
| | - Shutian Liu
- State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116024, China.
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26
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Tayler MCD, Sakellariou D. Low-cost, pseudo-Halbach dipole magnets for NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2017; 277:143-148. [PMID: 28285144 DOI: 10.1016/j.jmr.2017.03.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 03/01/2017] [Accepted: 03/02/2017] [Indexed: 05/27/2023]
Abstract
We present designs for compact, inexpensive and strong dipole permanent magnets aimed primarily at magnetic resonance applications where prepolarization and detection occur at different locations. Low-homogeneity magnets with a 7.5mm bore size and field up to nearly 2T are constructed using low-cost starting materials, standard workshop tools and only few hours of labor - an achievable project for a student or postdoc with spare time. As an application example we show how our magnet was used to polarize the nuclear spins in approximately 1mL of pure [13C]-methanol prior to detection of its high-resolution NMR spectrum at zero field (measurement field below 10-10T), where signals appear at multiples of the carbon-hydrogen spin-spin coupling frequency 1JCH=140.7(1)Hz.
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Affiliation(s)
- Michael C D Tayler
- Magnetic Resonance Research Center, Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, UK; Department of Physics, University of California, Berkeley, CA 94720, USA.
| | - Dimitrios Sakellariou
- NIMBE, CEA-CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
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27
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Chonlathep K, Sakamoto T, Sugahara K, Kondo Y. A simple and low-cost permanent magnet system for NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2017; 275:114-119. [PMID: 28043004 DOI: 10.1016/j.jmr.2016.12.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 12/13/2016] [Accepted: 12/19/2016] [Indexed: 06/06/2023]
Abstract
We have developed a simple, easy to build, and low-cost magnet system for NMR, of which homogeneity is about 4×10-4 at 57mT, with a pair of two commercially available ferrite magnets. This homogeneity corresponds to about 90Hz spectral resolution at 2.45MHz of the hydrogen Larmor frequency. The material cost of this NMR magnet system is little more than $100. The components can be printed by a 3D printer.
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Affiliation(s)
- K Chonlathep
- Grad. Sch. of Sci. and Eng., Kindai Univ., 577-8502 Higashi Osaka, Japan.
| | - T Sakamoto
- Dept. of Ele. and Eng., Kindai Univ., 577-8502 Higashi Osaka, Japan.
| | - K Sugahara
- Grad. Sch. of Sci. and Eng., Kindai Univ., 577-8502 Higashi Osaka, Japan; Dept. of Ele. and Eng., Kindai Univ., 577-8502 Higashi Osaka, Japan.
| | - Y Kondo
- Grad. Sch. of Sci. and Eng., Kindai Univ., 577-8502 Higashi Osaka, Japan; Dept. of Phys., Kindai Univ., 577-8502 Higashi Osaka, Japan.
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28
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McGinley JVM, Ristic M, Young IR. A permanent MRI magnet for magic angle imaging having its field parallel to the poles. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2016; 271:60-67. [PMID: 27552556 DOI: 10.1016/j.jmr.2016.08.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 08/05/2016] [Accepted: 08/05/2016] [Indexed: 06/06/2023]
Abstract
A novel design of open permanent magnet is presented, in which the magnetic field is oriented parallel to the planes of its poles. The paper describes the methods whereby such a magnet can be designed with a field homogeneity suitable for Magnetic Resonance Imaging (MRI). Its primary purpose is to take advantage of the Magic Angle effect in MRI of human extremities, particularly the knee joint, by being capable of rotating the direction of the main magnetic field B0 about two orthogonal axes around a stationary subject and achieve all possible angulations. The magnet comprises a parallel pair of identical profiled arrays of permanent magnets backed by a flat steel yoke such that access in lateral directions is practical. The paper describes the detailed optimization procedure from a target 150mm DSV to the achievement of a measured uniform field over a 130mm DSV. Actual performance data of the manufactured magnet, including shimming and a sample image, is presented. The overall magnet system mounting mechanism is presented, including two orthogonal axes of rotation of the magnet about its isocentre.
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Affiliation(s)
- John V M McGinley
- Imperial College London, Mechanical Engineering Department, South Kensington Campus, Exhibition Road, London SW7 2AZ, United Kingdom
| | - Mihailo Ristic
- Imperial College London, Mechanical Engineering Department, South Kensington Campus, Exhibition Road, London SW7 2AZ, United Kingdom.
| | - Ian R Young
- Imperial College London, Mechanical Engineering Department, South Kensington Campus, Exhibition Road, London SW7 2AZ, United Kingdom
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29
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Kausik R, Hürlimann MD. Sensitivity and resolution of two-dimensional NMR diffusion-relaxation measurements. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2016; 270:12-23. [PMID: 27389638 DOI: 10.1016/j.jmr.2016.06.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 06/14/2016] [Accepted: 06/15/2016] [Indexed: 06/06/2023]
Abstract
The performance of 2D NMR diffusion-relaxation measurements for fluid typing applications is analyzed. In particular, we delineate the region in the diffusion - relaxation plane that can be determined with a given gradient strength and homogeneity, and compare the performance of the single and double echo encoding with the stimulated echo diffusion encoding. We show that the diffusion editing based approach is able to determine the diffusion coefficient only if the relaxation time T2 exceeds a cutoff value T2,cutoff, that scales like T2,cutoff∝g(-2/3)D(-1/3). For stimulated echo encoding, the optimal diffusion encoding times (Td and δ), that provide the best diffusion sensitivity, rely only on the T1/T2 ratios and not on the diffusion coefficients of the fluids or the applied gradient strengths. Irrespective of T1, for high enough gradients (i.e. when γ(2)g(2)DT2(3)>10(2)), the Hahn echo based encoding is superior to encoding based on the stimulated echo. For weaker gradients, the stimulated echo is superior only if the T1/T2 ratio is much larger than 1. For single component systems, the diffusion sensitivity is not adversely impacted by the uniformity of the gradients and the diffusion distributions can be well measured. The presence of non-uniform gradients can affect the determination of the diffusion distributions when you have two fluids of comparable T2. In such situations the effective single component diffusion coefficient is always closer to the geometric mean diffusion coefficient of the two fluids.
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30
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Woflson H, Ahmad R, Twig Y, Williams B, Blank A. A magnetic resonance probehead for evaluating the level of ionizing radiation absorbed in human teeth. HEALTH PHYSICS 2015; 108:326-335. [PMID: 25627944 DOI: 10.1097/hp.0000000000000187] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A miniature electron spin resonance (ESR) probehead that includes a static field source and a microwave resonator for in vivo measurement of paramagnetic defects in tooth enamel was developed. These defects are known to be a good marker for quantifying the ionizing radiation dose absorbed in teeth. The probehead has a typical length of just 30 mm and total weight of 220 g. The patient "bites" into the probehead while the measurement procedure is being carried out. The probehead operates in pulsed mode at a frequency of ∼ 11.2 GHz and supplies a static magnetic field of ∼ 400 mT. A detailed design of the probehead is provided together with its specifications in terms of measurement volume and signal-to-noise ratio for a typical sample. A specially developed simulation program was used to predict the spatial distribution of the acquired signal under conditions of grossly inhomogeneous static and RF fields. Experimental results with irradiated incisor teeth validated the probehead's sensitivity, being able to detect signals in tooth irradiated by only 2 Gy. Subject to additional improvements and tests, this type of probehead can potentially have significant clinical applications ranging from mass triage following major nuclear events to routine occupational evaluation of ionizing radiation absorbed over long periods of time.
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Affiliation(s)
- Helen Woflson
- *Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel; †Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH, 43210; ‡The Geisel School of Medicine at Dartmouth, Departments of Medicine and Radiology, Lebanon, NH 03766
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31
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Mastikhin I, Barnhill M. Sensitization of a stray-field NMR to vibrations: a potential for MR elastometry with a portable NMR sensor. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2014; 248:1-7. [PMID: 25282441 DOI: 10.1016/j.jmr.2014.09.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 09/04/2014] [Accepted: 09/05/2014] [Indexed: 06/03/2023]
Abstract
An NMR signal from a sample in a constant stray field of a portable NMR sensor is sensitized to vibrations. The CPMG sequence is synchronized to vibrations so that the constant gradient becomes an "effective" square-wave gradient, leading to the vibration-induced phase accumulation. The integrating nature of the spot measurement, combined with the phase distribution due to a non-uniform gradient and/or a wave field, leads to a destructive interference, the drop in the signal intensity and changes in the echo train shape. Vibrations with amplitudes as small as 140 nm were reliably detected with the permanent gradient of 12.4 T/m. The signal intensity depends on the phase offset between the vibrations and the pulse sequence. This approach opens the way for performing elastometry and micro-rheology measurements with portable NMR devices beyond the walls of a laboratory. Even without synchronization, if a vibration frequency is comparable to 1/2TE of the CPMG sequence, the signal can be severely affected, making it important for potential industrial applications of stray-field NMR.
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Affiliation(s)
- Igor Mastikhin
- MRI Centre, Department of Physics, University of New Brunswick, Fredericton, New Brunswick E3B 5A3, Canada.
| | - Marie Barnhill
- MRI Centre, Department of Physics, University of New Brunswick, Fredericton, New Brunswick E3B 5A3, Canada
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Degradation of phosphate ester hydraulic fluid in power station turbines investigated by a three-magnet unilateral magnet array. SENSORS 2014; 14:6797-805. [PMID: 24736132 PMCID: PMC4029633 DOI: 10.3390/s140406797] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 03/25/2014] [Accepted: 03/28/2014] [Indexed: 11/25/2022]
Abstract
A three-magnet array unilateral NMR sensor with a homogeneous sensitive spot was employed for assessing aging of the turbine oils used in two different power stations. The Carr-Purcell-Meiboom-Gill (CPMG) sequence and Inversion Recovery-prepared CPMG were employed for measuring the 1H-NMR transverse and longitudinal relaxation times of turbine oils with different service status. Two signal components with different lifetimes were obtained by processing the transverse relaxation curves with a numeric program based on the Inverse Laplace Transformation. The long lifetime components of the transverse relaxation time T2eff and longitudinal relaxation time T1 were chosen to monitor the hydraulic fluid aging. The results demonstrate that an increase of the service time of the turbine oils clearly results in a decrease of T2eff,long and T1,long. This indicates that the T2eff,long and T1,long relaxation times, obtained from the unilateral magnetic resonance measurements, can be applied as indices for degradation of the hydraulic fluid in power station turbines.
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Mitchell J, Gladden LF, Chandrasekera TC, Fordham EJ. Low-field permanent magnets for industrial process and quality control. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2014; 76:1-60. [PMID: 24360243 DOI: 10.1016/j.pnmrs.2013.09.001] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Revised: 09/19/2013] [Accepted: 09/19/2013] [Indexed: 05/13/2023]
Abstract
In this review we focus on the technology associated with low-field NMR. We present the current state-of-the-art in low-field NMR hardware and experiments, considering general magnet designs, rf performance, data processing and interpretation. We provide guidance on obtaining the optimum results from these instruments, along with an introduction for those new to low-field NMR. The applications of lowfield NMR are now many and diverse. Furthermore, niche applications have spawned unique magnet designs to accommodate the extremes of operating environment or sample geometry. Trying to capture all the applications, methods, and hardware encompassed by low-field NMR would be a daunting task and likely of little interest to researchers or industrialists working in specific subject areas. Instead we discuss only a few applications to highlight uses of the hardware and experiments in an industrial environment. For details on more particular methods and applications, we provide citations to specialized review articles.
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Affiliation(s)
- J Mitchell
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, United Kingdom; Schlumberger Gould Research, High Cross, Madingley Road, Cambridge CB3 0EL, United Kingdom
| | - L F Gladden
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, United Kingdom.
| | - T C Chandrasekera
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, United Kingdom
| | - E J Fordham
- Schlumberger Gould Research, High Cross, Madingley Road, Cambridge CB3 0EL, United Kingdom
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Li X, Hugon C, Polesel-Maris J, Martinez V, Sakellariou D. Simple procedure for the fabrication of flexible NMR shim coils. CR CHIM 2013. [DOI: 10.1016/j.crci.2013.05.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Terada Y, Kono S, Ishizawa K, Inamura S, Uchiumi T, Tamada D, Kose K. 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. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 230:125-133. [PMID: 23475056 DOI: 10.1016/j.jmr.2013.02.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Revised: 01/31/2013] [Accepted: 02/05/2013] [Indexed: 06/01/2023]
Abstract
We adopted a combination of pieces of permanent magnets and a single-channel (SC) shim coil to shim the magnetic field in a magnetic resonance imaging system dedicated for skeletal age assessment of children. The target magnet was a 0.3-T open and compact permanent magnet tailored to the hand imaging of young children. The homogeneity of the magnetic field was first improved by shimming using pieces of permanent magnets. The residual local inhomogeneity was then compensated for by shimming using the SC shim coil. The effectiveness of the shimming was measured by imaging the left hands of human subjects and evaluating the image quality. The magnetic resonance images for the child subject clearly visualized anatomical structures of all bones necessary for skeletal age assessment, demonstrating the usefulness of combined shimming.
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Affiliation(s)
- Y Terada
- Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan.
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Geya Y, Kimura T, Fujisaki H, Terada Y, Kose K, Haishi T, Gemma H, Sekozawa Y. Longitudinal NMR parameter measurements of Japanese pear fruit during the growing process using a mobile magnetic resonance imaging system. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 226:45-51. [PMID: 23211549 DOI: 10.1016/j.jmr.2012.10.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Revised: 10/18/2012] [Accepted: 10/19/2012] [Indexed: 05/05/2023]
Abstract
Longitudinal nuclear magnetic resonance (NMR) parameter measurements of Japanese pear fruit (Pyrus pyrifolia Nakai, Kosui) were performed using an electrically mobile magnetic resonance imaging (MRI) system with a 0.2 T and 16 cm gap permanent magnet. To measure the relaxation times and apparent diffusion coefficients of the pear fruit in relation to their weight, seven pear fruits were harvested almost every week during the cell enlargement period and measured in a research orchard. To evaluate the in situ relaxation times, six pear fruits were longitudinally measured for about two months during the same period. The measurements for the harvested samples showed good agreement with the in situ measurements. From the measurements of the harvested samples, it is clear that the relaxation rates of the pear fruits linearly change with the inverse of the linear dimension of the fruits, demonstrating that the relaxation mechanism is a surface relaxation. We therefore conclude that the mobile MRI system is a useful device for measuring the NMR parameters of outdoor living plants.
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Affiliation(s)
- Yuto Geya
- Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 3058573, Japan
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Koptyug IV. MRI of mass transport in porous media: drying and sorption processes. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2012; 65:1-65. [PMID: 22781314 DOI: 10.1016/j.pnmrs.2011.12.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Accepted: 12/05/2011] [Indexed: 06/01/2023]
Affiliation(s)
- Igor V Koptyug
- International Tomography Center, SB RAS, 3A Institutskaya Str., Novosibirsk 630090, Russian Federation.
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Marble AE. Optimization of echo amplitudes resulting from a series of 90° pulses in an inhomogeneous static field. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 216:37-42. [PMID: 22329972 DOI: 10.1016/j.jmr.2011.12.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Revised: 11/22/2011] [Accepted: 12/22/2011] [Indexed: 05/31/2023]
Abstract
In an inhomogeneous static field, the pulse sequence 90°(x)-(τ-90°(y)-τ)(n) results in a train of echoes, the amplitudes of which settle to be proportional to M(0)/2 after a transient period. Analysis of the spin dynamics of the general τ-β°-τ refocusing cycle reveals that for ideal RF pulses, adding a preparation pulse followed by a delay to the above sequence can either eliminate the transient behavior, or increase the asymptotic echo intensity. This is achieved by controlling the alignment between the magnetization m and the rotation axis of the refocusing cycle. The effect of preparations pulses is demonstrated experimentally in the fringe field of a single sided magnet array. It is shown that for this instrument, transient effects in the echo train can be reduced, and asymptotic signal increased. Spin dynamics calculations indicate that the sequences are robust to finite RF pulse widths, but some discrepancy between theory and experiment is observed due to B(1) inhomogeneity. Refocusing sequences of the type studied here are useful in cases where experimental considerations, such as RF power limits, preclude the use of a 180° pulse in the refocusing cycle.
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Affiliation(s)
- Andrew E Marble
- Department of Systems and Computer Engineering, Carleton University, Mackenzie Building, Room 4462, 1125 Colonel By Dr., Ottawa, Ontario, Canada K1S 5B6.
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Van Landeghem M, Danieli E, Perlo J, Blümich B, Casanova F. Low-gradient single-sided NMR sensor for one-shot profiling of human skin. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 215:74-84. [PMID: 22244451 DOI: 10.1016/j.jmr.2011.12.010] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Revised: 12/13/2011] [Accepted: 12/14/2011] [Indexed: 05/31/2023]
Abstract
This paper describes a shimming approach useful to reduce the gradient strength of the magnetic field generated by single-sided sensors simultaneously maximizing its uniformity along the lateral directions of the magnet. In this way, the thickness of the excited sensitive volume can be increased without compromising the depth resolution of the sensor. By implementing this method on a standard U-shaped magnet, the gradient strength was reduced one order of magnitude. In the presence of a gradient of about 2 T/m, slices of 2mm could be profiled with a resolution that ranges from 25 μm at the center of the slice to 50 μm at the borders. This sensor is of particular advantage for applications, where the scanning range is of the order of the excited slice. In those cases, the full profile is measured in a single excitation experiment, eliminating the need for repositioning the excited slice across the depth range to complete the profile as occurs with standard high gradient sensors. Besides simplifying the experimental setup, the possibility to move from a point-by-point measurement to the simultaneous acquisition of the full profile led to the shortening of the experimental time. A further advantage of performing the experiment under a smaller static gradient is a reduction of the diffusion attenuation affecting the signal decay measured with a CPMG sequence, making it possible to measure the T(2) of samples with high diffusivity (comparable to the water diffusivity). The performance of the sensor in terms of resolution and sensitivity is first evaluated and compared with conventional singled-sided sensors of higher gradient strength using phantoms of known geometry and relaxation times. Then, the device is used to profile the structure of human skin in vivo. To understand the contrast between the different skin layers, the distribution of relaxation times T(2) and diffusion coefficients is spatially resolved along the depth direction.
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Chang WH, Chung CY, Chen JH, Hwang DW, Hsu CH, Yao C, Hwang LP. Simple mobile single-sided NMR apparatus with a relatively homogeneous B0 distribution. Magn Reson Imaging 2011; 29:869-76. [DOI: 10.1016/j.mri.2011.02.026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2010] [Revised: 12/20/2010] [Accepted: 02/20/2011] [Indexed: 10/18/2022]
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García-Naranjo JC, Mastikhin IV, Colpitts BG, Balcom BJ. A unilateral magnet with an extended constant magnetic field gradient. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2010; 207:337-344. [PMID: 21030276 DOI: 10.1016/j.jmr.2010.09.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Revised: 09/29/2010] [Accepted: 09/29/2010] [Indexed: 05/30/2023]
Abstract
Unilateral magnetic resonance (UMR) has become, in different research areas, a powerful tool to interrogate samples of arbitrary size. Numerous designs have been suggested in the literature to produce the desired magnetic field distributions, including designs which feature constant magnetic field gradients suitable for diffusion and profiling experiments. This work presents a new approach which features extended constant magnetic field gradients with a three magnet array. Constant gradients of more than 3cm extent can be achieved in a very simple, compact and safe design. Diffusion measurements from different positions over the magnet are presented in addition to practical applications for reservoir core plug characterization. The idea of a solenoid as a probe for specific measurements in UMR is introduced. Simple profiling experiments are also presented.
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Affiliation(s)
- Juan C García-Naranjo
- MRI Centre, Department of Physics, P.O. Box 4400, University of New Brunswick, Fredericton, NB, Canada E3B 5A3
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Chang WH, Chen JH, Hwang LP. Single-sided mobile NMR apparatus using the transverse flux of a single permanent magnet. Magn Reson Imaging 2010; 28:129-38. [DOI: 10.1016/j.mri.2009.05.039] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2008] [Revised: 04/26/2009] [Accepted: 05/10/2009] [Indexed: 10/20/2022]
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45
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Petrov OV, Hay J, Mastikhin IV, Balcom BJ. Fat and moisture content determination with unilateral NMR. Food Res Int 2008. [DOI: 10.1016/j.foodres.2008.05.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Manz B, Benecke M, Volke F. A simple, small and low cost permanent magnet design to produce homogeneous magnetic fields. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2008; 192:131-138. [PMID: 18314366 DOI: 10.1016/j.jmr.2008.02.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Revised: 02/07/2008] [Accepted: 02/08/2008] [Indexed: 05/26/2023]
Abstract
A new portable, pocket-size NMR probe based on a novel permanent magnet arrangement is presented. It is based on a Halbach-type magnet design which mimics the field of a spherical dipole by using cylindrical bar and ring magnets. The magnet system is made up of only three individual magnets, and most field calculations and optimisations can be performed analytically. A prototype system has been built using a set of small, off the shelf commercially available permanent magnets. Proton linewidths of 50 ppm FWHM could be achieved at a field strength of 1T. Calculations show that with custom-sized permanent magnets, linewidths of less than 1 ppm can be achieved over sample volumes of up to 1 mm3, which would in theory enable chemical shift resolved proton spectroscopy on mass-limited samples. But even with the achieved linewidth of 50 ppm, this can be a useful portable sensor for small amounts of liquid samples with restricted molecular mobility, like gels, polymers or high viscosity liquids.
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Affiliation(s)
- B Manz
- Arbeitsgruppe Magnetische Resonanz, Fraunhofer-Institut für Biomedizinische Technik, Ensheimer Strasse 48, 66386 St. Ingbert, Germany.
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