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Tritrakarn T, Yamamoto K, Takahashi M, Okamura T. New unifying metric for NMR/MRI probe evaluation based on optimized solenoid coil geometry. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2024; 358:107602. [PMID: 38061293 DOI: 10.1016/j.jmr.2023.107602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 11/21/2023] [Accepted: 11/28/2023] [Indexed: 01/21/2024]
Abstract
A three-dimensional numerical simulation of the magnetic field distribution and Bloch equations for arbitrary radio frequency (RF) coils is developed and compared against nuclear magnetic resonance (NMR) experimental results to evaluate the NMR signal intensity. Because NMR is inherently insensitive and its signal intensity is dependent on RF coil geometry, the investigation of RF coil geometry to maximize signal intensity for a given sample volume is important for improving the signal-to-noise ratio (SNR) and shortening the accumulation time. The developed simulation can optimize the RF coil geometry, specifically a single-layer solenoid coil with a constant winding pitch, and the result of the solenoid coil simulation serves as a new unifying metric for evaluating NMR/MRI probes. It is found that the most efficient sample aspect ratio (ratio of sample length to sample diameter) and pitch to wire diameter ratio for the highest signal intensity are around 2.2 and 1.65, respectively. Some discrepancies from the solenoid coil geometry ratios for higher signal intensity in previous studies can be explained by the difference in the gap between the inner diameter of the solenoid coil and the sample diameter. These results are confirmed through NMR signal intensity expressed in voltages with three approaches: 3D simulation, experiment, and estimation based on probe parameters. The simulated signal intensity shows a maximum error of approximately 5 % and an average error of 1 % when compared to the experimental results. This result suggests that the developed methods hold the potential for application in quantitative NMR (qNMR) without relying on standard reference materials. Finally, this study introduces a standardized geometry for the optimized solenoid coil for higher signal intensity and uses it to establish an evaluation metric called the signal-to-optimized-solenoid-signal ratio (3SR). The 3SR addresses the volume-dependence problem in conventional metrics like SNR and SNR per sample volume. It provides a standardized approach for the unified evaluation of all RF coils and probe designs, regardless of sample volume and measurement frequency. Therefore, 3SR can be utilized as a useful metric in the search for optimal coil geometry, while metrics such as SNR or SNR per sample volume are currently used for such purpose. This metric is expected to be useful for NMR/magnetic resonance imaging (MRI) users and developers.
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Affiliation(s)
- Techit Tritrakarn
- School of Engineering, Department of Mechanical Engineering, Tokyo Institute of Technology, 4259 Nagatusta-cho, Midori-ku, Yokohama, Kanagawa 226-8502, Japan.
| | - Kouki Yamamoto
- School of Engineering, Department of Mechanical Engineering, Tokyo Institute of Technology, 4259 Nagatusta-cho, Midori-ku, Yokohama, Kanagawa 226-8502, Japan
| | - Masato Takahashi
- Laboratory for Advanced NMR Application and Development, RIKEN Center for Biosystems Dynamics Research, tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Tetsuji Okamura
- School of Engineering, Department of Mechanical Engineering, Tokyo Institute of Technology, 4259 Nagatusta-cho, Midori-ku, Yokohama, Kanagawa 226-8502, Japan
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Thomas JN, Johnston TL, Litvak IM, Ramaswamy V, Merritt ME, Rocca JR, Edison AS, Brey WW. Implementing High Q-Factor HTS Resonators to Enhance Probe Sensitivity in 13C NMR Spectroscopy. JOURNAL OF PHYSICS. CONFERENCE SERIES 2022; 2323:012030. [PMID: 36187328 PMCID: PMC9524303 DOI: 10.1088/1742-6596/2323/1/012030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Nuclear magnetic resonance spectroscopy (NMR) probes using thin-film high temperature superconducting (HTS) resonators provide exceptional mass sensitivity in small-sample NMR experiments for natural products chemistry and metabolomics. We report improvements in sensitivity to our 1.5 mm 13C-optimized NMR probe based on HTS resonators. The probe has a sample volume of 35 microliters and operates in a 14.1 T magnet. The probe also features HTS resonators for 1H transmission and detection and the 2H lock. The probe utilizes a 13C resonator design that provides greater efficiency than our previous design. The quality factor of the new resonator in the 14.1 T background field was measured to be 4,300, which is over 3x the value of the previous design. To effectively implement the improved quality factor, we demonstrate the effect of adding a shorted transmission line stub to increase the bandwidth and reduce the rise/fall time of 13C irradiation pulses. Initial NMR measurements verify 13C NMR sensitivity is significantly improved while preserving detection bandwidth. The probe will be used for applications in metabolomics.
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Affiliation(s)
- J N Thomas
- National High Magnetic Field Laboratory, Tallahassee FL, USA
| | - T L Johnston
- National High Magnetic Field Laboratory, Tallahassee FL, USA
| | - I M Litvak
- National High Magnetic Field Laboratory, Tallahassee FL, USA
| | | | | | - J R Rocca
- University of Florida, Gainesville FL, USA
| | | | - W W Brey
- National High Magnetic Field Laboratory, Tallahassee FL, USA
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Thomas JN, Ramaswamy V, Litvak IM, Johnston TL, Edison AS, Brey WW. Progress Towards a Higher Sensitivity 13C-Optimized 1.5 mm HTS NMR Probe. IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY : A PUBLICATION OF THE IEEE SUPERCONDUCTIVITY COMMITTEE 2021; 31:1500504. [PMID: 33867781 PMCID: PMC8045891 DOI: 10.1109/tasc.2021.3061042] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Nuclear magnetic resonance (NMR) probes using thin-film high temperature superconducting (HTS) resonators offer high sensitivity and are particularly suitable for small-sample applications. We are developing an improved 1.5 mm HTS NMR probe designed for operation at 14.1 T and optimized for 13C detection. The total sample volume is about 35 μL and the active sample volume is 20 μL. The probe employs HTS resonators for 13C and 1H transmission and detection and the 2H lock. We examine the interactions of multiple superconducting resonators and normal metal tuning loops on coil resonance frequency and probe sensitivity. We test a recently introduced 13C resonator design, engineered to significantly increase 13C detection sensitivity over previous all-HTS probes. At zero field, we observe a 13C quality factor of 6000 which is several times higher than previous resonators. In this work the coil design considerations and probe build-out procedure are discussed.
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Affiliation(s)
- Jeremy N Thomas
- National High Magnetic Laboratory and the Department of Physics, Florida State University, Tallahassee, FL 32310 USA
| | | | - Ilya M Litvak
- National High Magnetic Laboratory, Florida State University, Tallahassee, FL 32310 USA
| | - Taylor L Johnston
- National High Magnetic Laboratory and the Department of Chemistry, Florida State University, Tallahassee, FL 32310 USA
| | | | - William W Brey
- National High Magnetic Laboratory, Florida State University, Tallahassee, FL 32310 USA
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Thomas JN, Ramaswamy V, Johnston TL, Belc DC, Freytag N, Hornak LA, Edison AS, Brey WW. Modeling the Resonance Shifts Due to Coupling Between HTS Coils in NMR Probes. JOURNAL OF PHYSICS. CONFERENCE SERIES 2020; 1559. [PMID: 33868445 PMCID: PMC8049185 DOI: 10.1088/1742-6596/1559/1/012022] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Nuclear magnetic resonance (NMR) probes using thin-film HTS coils offer high sensitivity and are particularly suitable for small-sample applications. Typically, HTS probes are optimized for the detection of multiple nuclei and require several coils to be located within a small volume near the sample. Coupling between the coils shifts coil resonances and complicates coil trimming when tuning HTS probes. We have modeled the magnetic coupling between the coils of a 1.5-mm all-HTS NMR probe with 13C, 1H, and 2H channels. By measuring the magnetic coupling coefficients between individual coils, we solve the general coupling matrix given by KVL for six coupled resonators. Our results indicate that required trims can be accurately predicted by applying single coil trimming simulations to this magnetic coupling model. Use of the magnetic coupling model significantly improves the efficiency of tuning HTS probes.
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Affiliation(s)
- J N Thomas
- National High Magnetic Field Laboratory, Florida State University, Tallahassee FL, USA
| | | | - T L Johnston
- National High Magnetic Field Laboratory, Florida State University, Tallahassee FL, USA
| | - D C Belc
- National High Magnetic Field Laboratory, Florida State University, Tallahassee FL, USA
| | - N Freytag
- Bruker Biospin, Faellanden, Switzerland
| | | | | | - W W Brey
- National High Magnetic Field Laboratory, Florida State University, Tallahassee FL, USA
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Edison AS, Le Guennec A, Delaglio F, Kupče Ē. Practical Guidelines for 13C-Based NMR Metabolomics. Methods Mol Biol 2019; 2037:69-95. [PMID: 31463840 DOI: 10.1007/978-1-4939-9690-2_5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
We present an overview of 13C-based NMR metabolomics. At first glance, the low sensitivity of 13C relative to 1H NMR might seem like too great an obstacle to use this approach. However, there are several advantages to 13C NMR, whether samples can be isotopically enriched or not. At natural abundance, peaks are sharp and largely resolved, and peak frequencies are more stable to pH and other sample conditions. Statistical approaches can be used to obtain C-C and C-H correlation maps, which greatly aid in compound identification. With 13C isotopic enrichment, other experiments are possible, including both 13C-J-RES and INADEQUATE, which can be used for de novo identification of metabolites not in databases.NMR instrumentation and software has significantly improved, and probes are now commercially available that can record useful natural abundance 1D 13C spectra from real metabolomics samples in 2 h or less. Probe technology continues to improve, and the next generation should be even better. Combined with new methods of simultaneous data acquisition, which allows for two or more 1D or 2D NMR experiments to be collected using multiple receivers, very rich datasets can be collected in a reasonable amount of time that should improve metabolomics data analysis and compound identification.
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Affiliation(s)
- Arthur S Edison
- Department of Biochemistry, University of Georgia, Athens, GA, USA. .,Department of Genetics, University of Georgia, Athens, GA, USA. .,Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA.
| | - Adrien Le Guennec
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA.,NMR Facility, Guy's Campus, King's College London, London, UK
| | - Frank Delaglio
- Institute for Bioscience and Biotechnology Research, National Institute of Standards and Technology, University of Maryland, Rockville, MD, USA
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Combined Conformal Strongly-Coupled Magnetic Resonance for Efficient Wireless Power Transfer. ENERGIES 2017. [DOI: 10.3390/en10040498] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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