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Ariando D, Mandal S. A pulsed current-mode class-D low-voltage high-bandwidth power amplifier for portable NMR systems. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 348:107367. [PMID: 36689787 DOI: 10.1016/j.jmr.2023.107367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 01/04/2023] [Accepted: 01/05/2023] [Indexed: 06/17/2023]
Abstract
Low-field NMR has seen growing interest in recent years, especially for portable applications. The lower homogeneity magnets used for portable applications require short RF pulses to ensure enough transmit bandwidth to excite the sample volume and also support short echo periods. Furthermore, the preferred use of a high-Q coil to improve signal-to-noise ratio (SNR) prolongs the pulse transients. Thus, at such low Larmor frequencies, the excitation pulse transients become comparable or longer than the pulse length, such that the transmit bandwidth begins to limit measurement SNR. This paper describes the design of a pulsed current-mode class-D power (PCMCD) transmitter that addresses this issue by generating high power in a tuned sample coil while maintaining short transients, thus resulting in high output bandwidth. The transmitter also uses a charge recycling mechanism to maximize power efficiency for RF train excitation, which also results in faster pulse repetition rate and reduces allowable echo time. Experimental results from a small form-factor PCMCD transmitter are presented. This design generates a peak RF power of 240 W into a 9.16 μH coil at 4 MHz while operating off a single 12 V power supply. NMR measurement results using the transmitter are also described, showing minimum achievable echo time of 70 μs and 25 μs depending on the transmitter mode of operation.
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Affiliation(s)
- David Ariando
- University of Florida, 1064 Center Drive, Gainesville, FL 32611, USA.
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2
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Bidinosti CP, Tastevin G, Nacher PJ. Generating accurate tip angles for NMR outside the rotating-wave approximation. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2022; 345:107306. [PMID: 36434882 DOI: 10.1016/j.jmr.2022.107306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 09/26/2022] [Accepted: 09/28/2022] [Indexed: 06/16/2023]
Abstract
The generation of accurate tip angles is critical for many applications of nuclear magnetic resonance. In low static field, with a linear rather than circular polarized rf field, the rotating-wave approximation may no longer hold and significant deviations from expected trajectories on the Bloch sphere can occur. For rectangular rf pulses, the effects depend strongly on the phase of the rf field and can be further compounded by transients at the start and end of the pulse. The desired terminus can be still be achieved, however, through the application of a phase-dependent Bloch-Siegert shift and appropriate consideration of pulse timings. For suitably shaped rf pulses, the Bloch-Siegert shift is largely phase independent, but its magnitude can vary significantly depending on details of the pulse shape as well as the characteristics of the rf coil circuit. We present numerical simulations and low-field NMR experiments with 1H and 3He that demonstrate several main consequences and accompanying strategies that one should consider when wanting to generate accurate tip angles outside the validity of the rotating-wave approximation and in low static field.
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Affiliation(s)
| | - Geneviève Tastevin
- Laboratoire Kastler Brossel, ENS-Université PSL, CNRS, Sorbonne Université, Collège de France, 24 rue Lhomond, 75005 Paris, France
| | - Pierre-Jean Nacher
- Laboratoire Kastler Brossel, ENS-Université PSL, CNRS, Sorbonne Université, Collège de France, 24 rue Lhomond, 75005 Paris, France.
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3
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O'Neill KT, Hopper TAJ, Fridjonsson EO, Johns ML. Quantifying motional dynamics in nuclear magnetic resonance logging. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2022; 337:107167. [PMID: 35217380 DOI: 10.1016/j.jmr.2022.107167] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 01/06/2022] [Accepted: 02/08/2022] [Indexed: 06/14/2023]
Abstract
The motional dynamics of nuclear magnetic resonance (NMR) logging tools can significantly influence the measurement performance of such tools. NMR logging is used for geophysical evaluation in geological environments, primarily quantifying formation porosity and fluid volumes, as well as providing a qualitative estimation of permeability. NMR logging tools are conveyed via two main mechanisms; wireline logging and logging while drilling (LWD). We conduct detailed simulations to quantify the impact of tool motion on NMR measurements during logging. This involves conducting electromagnetic simulations which quantify the magnetic fields generated by a logging tool, and subsequently introducing motion profiles within the relevant spin dynamic calculations. This enables tool motional dynamics to be imposed on the signal acquisition. Several movement profiles are considered: linear axial movement to replicate wireline logging tool motion, as well as axial harmonic and lateral harmonic movement to simulate the shocks and vibrations experienced during logging while drilling. Lateral motion is observed to cause a greater degree of signal attenuation relative to axial motion due to the cylindrical shape of the excited volume. The magnitude of motion (e.g. the velocity of linear motion or the amplitude of harmonic motion) is demonstrated to increase the severity of signal attenuation, as expected. However, the frequency of harmonic motion demonstrates a more complex effect on the measured signal. The harmonic interaction between the motion frequency and measurement frequency (determined by the echo spacing) can cause wave interference which results in enhanced or diminished signal attenuation. Finally, we demonstrate that reducing both the magnetic field gradient as well as the echo spacing reduce the degree of signal attenuation observed during measurement. The results presented in this work demonstrate how the optimisation of key design parameters can be used to control the sensitivity of NMR logging tools towards motion.
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Affiliation(s)
- Keelan T O'Neill
- Department of Chemical Engineering, University of Western Australia, Crawley, WA 6009, Australia.
| | - Timothy A J Hopper
- RIG Technologies International Pty Ltd, 46 Beaconsfield Avenue, Midvale, WA 6056, Australia
| | - Einar O Fridjonsson
- Department of Chemical Engineering, University of Western Australia, Crawley, WA 6009, Australia
| | - Michael L Johns
- Department of Chemical Engineering, University of Western Australia, Crawley, WA 6009, Australia
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Greer M, Ariando D, Hurlimann M, Song YQ, Mandal S. Analytical models of probe dynamics effects on NMR measurements. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2021; 327:106975. [PMID: 33873092 DOI: 10.1016/j.jmr.2021.106975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 03/23/2021] [Accepted: 03/24/2021] [Indexed: 06/12/2023]
Abstract
This paper provides a detailed analysis of three common NMR probe circuits (untuned, tuned, and impedance-matched) and studies their effects on multi-pulse experiments, such as those based on the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence. The magnitude of probe dynamics effects on broadband refocusing pulses are studied as a function of normalized RF bandwidth. Finally, the probe circuit models are integrated with spin dynamics simulations to design hardware-specific RF excitation and refocusing pulses for optimizing user-specified metrics such as signal-to-noise ratio (SNR) in grossly inhomogeneous fields. Preliminary experimental results on untuned probes are also presented.
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Affiliation(s)
- Mason Greer
- Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106, USA.
| | - David Ariando
- University of Florida, 1064 Center Drive, Gainesville, FL 32611, USA.
| | | | - Yi-Qiao Song
- Massachusetts General Hospital, Charlestown, MA 02129, USA.
| | - Soumyajit Mandal
- University of Florida, 1064 Center Drive, Gainesville, FL 32611, USA.
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Parasram T, Daoud R, Xiao D. T 2 analysis using artificial neural networks. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2021; 325:106930. [PMID: 33640586 DOI: 10.1016/j.jmr.2021.106930] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Revised: 11/11/2020] [Accepted: 01/28/2021] [Indexed: 06/12/2023]
Abstract
Quantitative analysis of magnetic resonance signal lifetimes could reveal molecular scale information. However, it is non-trivial to recover the relaxation times from MR experiments in the multi-component exponential decay analysis. Constraints are required for the ill-posed problem in conventional inversion methods, which could lead to biased solutions. Artificial neural networks (ANNs) are a series of densely connected information processing nodes which cumulatively map a set of inputs to a set of outputs. They have proven to be universal approximators and powerful tools for solving complex nonlinear problems. In this work, ANNs were trained to recover T2 relaxation times. Both the discrete T2 spectrum and continuous T2 distribution were considered. Increased accuracy was achieved compared to the traditional methods. The continuous spectrum peak widths, generally not reliable in the traditional approach, could be determined accurately with ANN when the signal-to-noise ratio permitted.
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Affiliation(s)
- Tristhal Parasram
- Department of Physics, University of Windsor, 401 Sunset Avenue, Windsor, Canada
| | - Rebecca Daoud
- Department of Physics, University of Windsor, 401 Sunset Avenue, Windsor, Canada
| | - Dan Xiao
- Department of Physics, University of Windsor, 401 Sunset Avenue, Windsor, Canada.
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Fechete R, Morar IA, Moldovan D, Chelcea RI, Crainic R, Nicoară SC. Fourier and Laplace-like low-field NMR spectroscopy: The perspectives of multivariate and artificial neural networks analyses. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2021; 324:106915. [PMID: 33648679 DOI: 10.1016/j.jmr.2021.106915] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 12/20/2020] [Accepted: 01/17/2021] [Indexed: 06/12/2023]
Abstract
Low field Nuclear Magnetic Resonance (LF-NMR) is a rich source of information for a wide range of samples types. These can be hard or soft solids, such as plastics or elastomers; bulk liquids or liquids absorbed in porous materials, and can come from biomaterials, biological tissues, archaeological artifacts, cultural heritage objects. LF-NMR instruments present a significant advance especially for in situ, ex situ and in vivo measurement of relaxation and diffusion. Moreover, high resolution 1D and 2D spectroscopy, as well as magnetic resonance (MR) imaging are available in these fields. In this work we discuss the advanced analysis of the data measured in LF-NMR from the perspectives of tertiary level that implies the analysis on principal components (PCA), and on the quaternary analysis that uses an artificial neural network (ANN). The principles of PCA and ANN are largely discussed. For the PCA analysis, a series of 52 spectra were analyzed, having been recorded in vivo by LF-NMR. Of these spectra, 38 were generated from normal uterus, 7 by uterus tissue with endometrial cancer, and another 7 were obtained from tissues of women with uterine cervical cancer. The PC1 vs PC2 plot was further analyzed using an artificial neural network, and the results are presented as 2D maps of probability. Furthermore, the perspectives of applying an ANN to solve the problem of Laplace-like inversion are discussed. An example of such ANN was presented and the performance was discussed. Finally, a model of complex ANN, capable to sequentially solve this kind of problems specific to LF-NMR is proposed and discussed.
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Affiliation(s)
- Radu Fechete
- Technical University of Cluj-Napoca, 28 Memorandumului str. 400114, Cluj-Napoca, Romania; Babeş-Bolyai University, Faculty of Physics, Doctoral School, 1 Kogălniceanu str., 400084 Cluj-Napoca, Romania.
| | - Iris Adina Morar
- Babeş-Bolyai University, Faculty of Physics, Doctoral School, 1 Kogălniceanu str., 400084 Cluj-Napoca, Romania; IMOGEN, County Emergency Hospital, Cluj-Napoca, Romania
| | - Dumitrița Moldovan
- Technical University of Cluj-Napoca, 28 Memorandumului str. 400114, Cluj-Napoca, Romania
| | - Ramona Ioana Chelcea
- Technical University of Cluj-Napoca, 28 Memorandumului str. 400114, Cluj-Napoca, Romania
| | - Ramona Crainic
- Technical University of Cluj-Napoca, 28 Memorandumului str. 400114, Cluj-Napoca, Romania; Babeş-Bolyai University, Faculty of Physics, Doctoral School, 1 Kogălniceanu str., 400084 Cluj-Napoca, Romania
| | - Simona Cornelia Nicoară
- Technical University of Cluj-Napoca, 28 Memorandumului str. 400114, Cluj-Napoca, Romania; STEM Faculty, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
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Ropp C, Chen C, Greer M, Glickstein J, Mair L, Hale O, Ariando D, Jafari S, Hevaganinge A, Mandal S, Weinberg IN. Electropermanent magnets for variable-field NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 303:82-90. [PMID: 31026669 DOI: 10.1016/j.jmr.2019.04.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 04/15/2019] [Accepted: 04/16/2019] [Indexed: 06/09/2023]
Abstract
In this work, a dynamically tunable B0 field is used to perform variable-field NMR. The system consists of an array of electropermanent AlNiCo-5 magnets whose magnetizations are individually programmed using pulse-power control. This design allows the field strength to be varied for field-dispersion measurements. An ultra-broadband front-end is utilized that maintains efficient power transmission over a broad range of frequencies for robust operation without probe tuning. We perform T1-T2 correlation measurements at various B0 field strengths (0.5-2 MHz) and demonstrate discrimination of different dairy products. We observe variation in the frequency dependence of the proton spin-lattice relaxation for the different products as a function of the degree of protein hydration. This variable-field technique provides a low-cost alternative to fast field-cycling NMR and could open possibilities for novel contrast measurements and spatial encoding in magnetic resonance imaging.
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Affiliation(s)
- Chad Ropp
- Weinberg Medical Physics, 12156 Parklawn Dr, Rockville, MD 20852, USA
| | - Cheng Chen
- Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106, USA.
| | - Mason Greer
- Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106, USA
| | - Jarred Glickstein
- Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106, USA
| | - Lamar Mair
- Weinberg Medical Physics, 12156 Parklawn Dr, Rockville, MD 20852, USA
| | - Olivia Hale
- Weinberg Medical Physics, 12156 Parklawn Dr, Rockville, MD 20852, USA
| | - David Ariando
- Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106, USA
| | - Sahar Jafari
- Weinberg Medical Physics, 12156 Parklawn Dr, Rockville, MD 20852, USA
| | | | - Soumyajit Mandal
- Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106, USA.
| | - Irving N Weinberg
- Weinberg Medical Physics, 12156 Parklawn Dr, Rockville, MD 20852, USA
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Ariando D, Chen C, Greer M, Mandal S. An autonomous, highly portable NMR spectrometer based on a low-cost System-on-Chip (SoC). JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 299:74-92. [PMID: 30590351 DOI: 10.1016/j.jmr.2018.12.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 12/05/2018] [Accepted: 12/07/2018] [Indexed: 05/13/2023]
Abstract
This paper describes the development of a portable and self-optimizing NMR spectrometer based on a miniaturized custom analog front-end and a System-on-Chip (SoC)-based digital back-end. The SoC integrates a field-programmable gate array (FPGA) fabric with a hard processor running a Linux operating system, thus enabling fully-autonomous operation without the need for an external computer. In the proposed approach, data captured by the FPGA fabric during regular operation is transported to the hard processor using an integrated on-chip bus for further processing. The processed results are then used to automatically estimate parameter values that optimize a suitable cost function, such as signal-to-noise ratio (SNR) per unit time. Finally, the optimized values of both electrical and NMR-related tuning parameters (e.g., preamplifier gain and frequency response, pulse length and amplitude, operating frequency, etc.) are programmed back into the front-end and back-end hardware. Experimental NMR results from various samples in a ∼0.1 T permanent magnet are presented to verify the operation of the proposed spectrometer. These demonstrate on-board Laplace inversion and automated frequency tuning to compensate for temperature changes. Preliminary 14N NQR results are also presented.
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Affiliation(s)
- David Ariando
- Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
| | - Cheng Chen
- Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
| | - Mason Greer
- Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
| | - Soumyajit Mandal
- Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
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