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Karasawa T, Saikawa J, Munaka T, Kobayashi T. Homogeneous B0 coil design method for open-access ultra-low field magnetic resonance imaging: A simulation study. Magn Reson Imaging 2024; 112:128-135. [PMID: 38986889 DOI: 10.1016/j.mri.2024.07.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 06/10/2024] [Accepted: 07/03/2024] [Indexed: 07/12/2024]
Abstract
A multimodal brain function measurement system integrating functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) is expected to be a tool that will provide new insights into neuroscience. To integrate fMRI and MEG, an ultra-low-field MRI (ULF-MRI) scanner that can generate a static magnetic field (B0) with an electromagnetic coil and turn off the B0 during MEG measurements is desirable. While electromagnetic B0 coil has the above advantages, it also has a trade-off between size and the broadness of the magnetic field homogeneity. In this study, we proposed a method for designing a B0 multi-stage circular coil arrangement that determines the number of coils required to maximize magnetic field homogeneity and minimize the total wiring length of the coils. The optimized multi-stage coil arrangement had an external shape of 600 mm in diameter and a maximum height of 600 mm, with an aperture of 600 mm in diameter and 300 mm in height. The magnetic field homogeneity was <100 ppm over a 210 mm diameter spherical volume (DSV). Compared to a previous two coil pairs arrangement with the same magnetic field homogeneity, the diameter was 1/1.9 times smaller, indicating that the newly designed B0 coil arrangement realized a smaller size and wider magnetic field homogeneity.
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Affiliation(s)
- Tomohiro Karasawa
- Technology Research Laboratory, Shimadzu corporation, 3-9-4, Hikaridai, Seika-cho, Soraku-gun 619-0237, Japan
| | - Jiro Saikawa
- Technology Research Laboratory, Shimadzu corporation, 3-9-4, Hikaridai, Seika-cho, Soraku-gun 619-0237, Japan
| | - Tatsuya Munaka
- Technology Research Laboratory, Shimadzu corporation, 3-9-4, Hikaridai, Seika-cho, Soraku-gun 619-0237, Japan
| | - Tetsuo Kobayashi
- Office of Institutional Advancement and Communications, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501, Japan.
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2
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Roth BJ. Can MRI Be Used as a Sensor to Record Neural Activity? SENSORS (BASEL, SWITZERLAND) 2023; 23:1337. [PMID: 36772381 PMCID: PMC9918955 DOI: 10.3390/s23031337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 01/17/2023] [Accepted: 01/24/2023] [Indexed: 06/18/2023]
Abstract
Magnetic resonance provides exquisite anatomical images and functional MRI monitors physiological activity by recording blood oxygenation. This review attempts to answer the following question: Can MRI be used as a sensor to directly record neural behavior? It considers MRI sensing of electrical activity in the heart and in peripheral nerves before turning to the central topic: recording of brain activity. The primary hypothesis is that bioelectric current produced by a nerve or muscle creates a magnetic field that influences the magnetic resonance signal, although other mechanisms for detection are also considered. Recent studies have provided evidence that using MRI to sense neural activity is possible under ideal conditions. Whether it can be used routinely to provide functional information about brain processes in people remains an open question. The review concludes with a survey of artificial intelligence techniques that have been applied to functional MRI and may be appropriate for MRI sensing of neural activity.
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Affiliation(s)
- Bradley J Roth
- Department of Physics, Oakland University, Rochester, MI 48309, USA
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3
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Capiglioni M, Turco F, Wiest R, Kiefer C. Analysis of the robustness and dynamics of spin-locking preparations for the detection of oscillatory magnetic fields. Sci Rep 2022; 12:16965. [PMID: 36216858 PMCID: PMC9550815 DOI: 10.1038/s41598-022-21232-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Accepted: 09/23/2022] [Indexed: 12/29/2022] Open
Abstract
Extracting quantitative information of neuronal signals by non-invasive imaging is an outstanding challenge for understanding brain function and pathology. However, state-of-the-art techniques offer low sensitivity to deep electrical sources. Stimulus induced rotary saturation is a recently proposed magnetic resonance imaging sequence that detects oscillatory magnetic fields using a spin-lock preparation. Phantom experiments and simulations proved its efficiency and sensitivity, but the susceptibility of the method to field inhomogeneities is still not well understood. In this study, we simulated and analyzed the dynamic of three spin-lock preparations and their response to field inhomogeneities in the presence of a resonant oscillating field. We show that the composite spin-lock preparation is more robust against field variations within the double resonance effect. In addition, we tested the capability of the chosen composite spin-lock preparation to recover information about the spectral components of a composite signal. This study sets the bases to move one step further towards the clinical application of MR-based neuronal current imaging.
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Affiliation(s)
- Milena Capiglioni
- grid.5734.50000 0001 0726 5157Institute for Diagnostic and Interventional Neuroradiology, Support Center for Advanced Neuroimaging (SCAN), University of Bern, Freiburgstrasse 16, 3010 Bern, Switzerland
| | - Federico Turco
- grid.5734.50000 0001 0726 5157Institute for Diagnostic and Interventional Neuroradiology, Support Center for Advanced Neuroimaging (SCAN), University of Bern, Freiburgstrasse 16, 3010 Bern, Switzerland
| | - Roland Wiest
- grid.5734.50000 0001 0726 5157Institute for Diagnostic and Interventional Neuroradiology, Support Center for Advanced Neuroimaging (SCAN), University of Bern, Freiburgstrasse 16, 3010 Bern, Switzerland
| | - Claus Kiefer
- grid.5734.50000 0001 0726 5157Institute for Diagnostic and Interventional Neuroradiology, Support Center for Advanced Neuroimaging (SCAN), University of Bern, Freiburgstrasse 16, 3010 Bern, Switzerland
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4
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Towards robust in vivo quantification of oscillating biomagnetic fields using Rotary Excitation based MRI. Sci Rep 2022; 12:15375. [PMID: 36100634 PMCID: PMC9469076 DOI: 10.1038/s41598-022-19275-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 08/26/2022] [Indexed: 11/28/2022] Open
Abstract
Spin-lock based functional magnetic resonance imaging (fMRI) has the potential for direct spatially-resolved detection of neuronal activity and thus may represent an important step for basic research in neuroscience. In this work, the corresponding fundamental effect of Rotary EXcitation (REX) is investigated both in simulations as well as in phantom and in vivo experiments. An empirical law for predicting optimal spin-lock pulse durations for maximum magnetic field sensitivity was found. Experimental conditions were established that allow robust detection of ultra-weak magnetic field oscillations with simultaneous compensation of static field inhomogeneities. Furthermore, this work presents a novel concept for the emulation of brain activity utilizing the built-in MRI gradient system, which allows REX sequences to be validated in vivo under controlled and reproducible conditions. Via transmission of Rotary EXcitation (tREX), we successfully detected magnetic field oscillations in the lower nano-Tesla range in brain tissue. Moreover, tREX paves the way for the quantification of biomagnetic fields.
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5
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Serša I. Electric Current Detection Based on the MR Signal Magnitude Decay. Magn Reson Med 2022; 88:1282-1291. [PMID: 35510691 PMCID: PMC9325414 DOI: 10.1002/mrm.29278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 04/03/2022] [Accepted: 04/04/2022] [Indexed: 11/18/2022]
Abstract
Purpose Conventional current density imaging method, which relies on the detection of the magnetic field induced by the current in an image phase, is demanding and difficult to perform. In this study, a much simpler signal‐magnitude‐decay (SMD)–based current detection method is proposed. Methods Conductive test and biological samples were imaged at various TE times using the gradient‐ or spin‐echo imaging sequences with superimposed constant or bipolar currents, respectively. The SMD curve was sampled for each image voxel, which enabled voxel‐vise current density calculation by fitting an appropriate SMD model curve to the measured SMD curve. Effect of the voxel size on the signal decay and precision of the current density calculation was studied as well. Results It was shown theoretically, as well as verified by experiments on test and biological samples, that the current flowing though the sample creates an inhomogeneous magnetic field, which, as a consequence has a faster signal decay. Estimated current density from the measured signal decay increase agreed reasonably well with the actual current density, especially with the larger voxel sizes and longer times to signal acquisition. The sensitivity of the SMD method is up to 1/6 the sensitivity of the current density imaging method. Conclusion SMD method of current detection is not limited to any particular sample orientation or geometry, and any pulse sequence capable of acquisition of the current‐induced signal evolution in a voxel can be used for it. This widens the scope of its application from tissues to in vivo studies on animals and humans.
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Affiliation(s)
- Igor Serša
- Jožef Stefan Institute, Ljubljana, Slovenia.,Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
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Ueda H, Ito Y, Oida T, Taniguchi Y, Kobayashi T. Magnetic resonance imaging simulation with spin-lock preparations to detect tiny oscillatory magnetic fields. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2021; 324:106910. [PMID: 33482529 DOI: 10.1016/j.jmr.2020.106910] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 11/27/2020] [Accepted: 12/25/2020] [Indexed: 06/12/2023]
Abstract
Spin-lock preparation was studied to detect tiny oscillatory magnetic fields such as a neural magnetic field without the blood oxygen level-dependent effect. This approach is a direct measurement and independent of static magnetic field strength. Accordingly, it is anticipated as a feasible functional magnetic resonance imaging (fMRI) in low and ultra-low-field MRI. Several reports have been published on spin-lock preparation but reports on imaging simulation are rare. Research in this area can assist in investigating magnetic resonance signal changes and, accordingly, can help to develop new spin-lock methods. In this study, we propose an imaging simulation method with an analytical solution using the Bloch equation. To demonstrate the feasibility of our proposed method, we compared simulated images with experimental results in which the number of sub-voxels and the amplitude and phase of the target oscillatory magnetic fields varied. In addition, we also applied graphics processing unit parallel computing and investigated the feasibility of avoiding an impracticable calculation time by doing so.
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Affiliation(s)
- Hiroyuki Ueda
- Department of Electrical Engineering, Graduate School of Engineering, Kyoto University, Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
| | - Yosuke Ito
- Department of Electrical Engineering, Graduate School of Engineering, Kyoto University, Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Takenori Oida
- Central Research Laboratory, Hamamatsu Photonics K.K., Japan
| | - Yo Taniguchi
- Research & Development Group, Hitachi, Ltd., Japan
| | - Tetsuo Kobayashi
- Department of Electrical Engineering, Graduate School of Engineering, Kyoto University, Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
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7
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Sogabe T, Ueda H, Ito Y, Taniguchi Y, Kobayashi T. Dependence of stimulus-induced rotary saturation on the direction of target oscillating magnetic fields: A phantom and simulation study. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 321:106849. [PMID: 33128915 DOI: 10.1016/j.jmr.2020.106849] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 09/23/2020] [Accepted: 10/09/2020] [Indexed: 06/11/2023]
Abstract
Several noninvasive techniques for the direct measurement of the neuronal activity using magnetic resonance imaging (MRI) have recently been reported. As a promising candidate, we focus on a spin-lock MRI sequence (i.e., stimulus-induced rotary saturation (SIRS)) directly measuring a tiny oscillating magnetic field. Previous phantom studies on SIRS have applied the target oscillating magnetic field parallel to the direction of the static magnetic field B0. However, in practice, the neuromagnetic fields are not always aligned in the same direction as in such a condition. This study investigates the MR signal changes during SIRS when the target magnetic field direction is not the same as that of the B0 field through both phantom experiments and Bloch simulations. The experimental results indicate that only the target magnetic field component along the B0 field affects the signal change, indicating that SIRS has partial sensitivity, even if the target magnetic fields are tilted from the B0 field. Furthermore, the simulation results show good agreements with the experimental results. These results clarify the sensitivity direction of SIRS-based fMRI and lead to the possibility that the direction of the generated neuromagnetic fields can be estimated, such that we can separate directional information from the other information contained in neuromagnetic fields (e.g., phase information).
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Affiliation(s)
- Tomoyuki Sogabe
- Department of Electrical Engineering, Graduate School of Engineering, Kyoto University, Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Hiroyuki Ueda
- Department of Electrical Engineering, Graduate School of Engineering, Kyoto University, Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Yosuke Ito
- Department of Electrical Engineering, Graduate School of Engineering, Kyoto University, Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Yo Taniguchi
- Research & Development Group, Hitachi, Ltd., Japan
| | - Tetsuo Kobayashi
- Department of Electrical Engineering, Graduate School of Engineering, Kyoto University, Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
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8
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Ueda H, Ito Y, Oida T, Taniguchi Y, Kobayashi T. Detection of tiny oscillatory magnetic fields using low-field MRI: A combined phantom and simulation study. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 319:106828. [PMID: 33002769 DOI: 10.1016/j.jmr.2020.106828] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 08/28/2020] [Accepted: 09/05/2020] [Indexed: 06/11/2023]
Abstract
We demonstrated the feasibility of the spin-lock preparation sequence using low-field magnetic resonance (MR) imaging that prevents interference from blood-oxygenation-level-dependent effects. We focused on two spin-lock preparations: spin-lock Mz (SL-Mz) and stimulus-induced rotary saturation (SIRS) and analyzed the magnetization dynamics during the sequences using the Bloch equation. Next, we performed phantom experiments using a loop coil to investigate the MR signal change as a function of the target signal strength and phase. Furthermore, we performed curve fittings to consider the radio frequency, which agreed with the experimental results. Then, we investigated the detectable strength of the magnetic field, and the SL-Mz detected a signal strength of 2.34 nT. In conclusion, our experimental results showed good agreement with the results obtained using the Bloch equation.
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Affiliation(s)
- Hiroyuki Ueda
- Department of Electrical Engineering, Graduate School of Engineering, Kyoto University, Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
| | - Yosuke Ito
- Department of Electrical Engineering, Graduate School of Engineering, Kyoto University, Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Takenori Oida
- Central Research Laboratory, Hamamatsu Photonics K.K, Japan
| | - Yo Taniguchi
- Research & Development Group, Hitachi, Ltd, Japan
| | - Tetsuo Kobayashi
- Department of Electrical Engineering, Graduate School of Engineering, Kyoto University, Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
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9
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Sveinsson B, Koonjoo N, Zhu B, Witzel T, Rosen MS. Detection of nanotesla AC magnetic fields using steady-state SIRS and ultra-low field MRI. J Neural Eng 2020; 17:034001. [PMID: 32268305 DOI: 10.1088/1741-2552/ab87fe] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Functional magnetic resonance imaging (fMRI) is commonly used to measure brain activity through the blood oxygen level dependent (BOLD) signal mechanism, but this only provides an indirect proxy signal to neuronal activity. Magnetoencephalography (MEG) provides a more direct measurement of the magnetic fields created by neuronal currents in the brain, but requires very specialized hardware and only measures these fields at the scalp. Recently, progress has been made to directly detect neuronal fields with MRI using the stimulus-induced rotary saturation (SIRS) effect, but interference from the BOLD response complicates such measurements. Here, we describe an approach to detect nanotesla-level, low-frequency alternating magnetic fields with an ultra-low field (ULF) MRI scanner, unaffected by the BOLD signal. APPROACH A steady-state implementation of the stimulus-induced rotary saturation (SIRS) method is developed. The method is designed to generate a strong signal at ultra-low magnetic field as well as allowing for efficient signal averaging, giving a high contrast-to-noise ratio (CNR). The method is tested in computer simulations and in phantom scans. MAIN RESULTS The simulations and phantom scans demonstrated the ability of the method to measure magnetic fields at different frequencies at ULF with a stronger contrast than non-steady-state approaches. Furthermore, the rapid imaging functionality of the method reduced noise efficiently. The results demonstrated sufficient CNR down to 7 nT, but the sensitivity will depend on the imaging parameters. SIGNIFICANCE A steady-state SIRS method is able to detect low-frequency alternating magnetic fields at ultra-low main magnetic field strengths with a large signal response and contrast-to-noise, presenting an important step in sensing biological fields with ULF MRI.
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Affiliation(s)
- Bragi Sveinsson
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, United States of America. Department of Radiology, Harvard Medical School, Boston, MA, United States of America. Author to whom any correspondence should be addressed
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10
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Ito Y, Ueno M, Kobayashi T. Neural magnetic field dependent fMRI toward direct functional connectivity measurements: A phantom study. Sci Rep 2020; 10:5463. [PMID: 32214147 PMCID: PMC7096527 DOI: 10.1038/s41598-020-62277-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Accepted: 03/10/2020] [Indexed: 11/16/2022] Open
Abstract
Recently, the main issue in neuroscience has been the imaging of the functional connectivity in the brain. No modality that can measure functional connectivity directly, however, has been developed yet. Here, we show the novel MRI sequence, called the partial spinlock sequence toward direct measurements of functional connectivity. This study investigates a probable measurement of phase differences directly associated with functional connectivity. By employing partial spinlock imaging, the neural magnetic field might influence the magnetic resonance signals. Using simulation and phantom studies to model the neural magnetic fields, we showed that magnetic resonance signals vary depending on the phase of an externally applied oscillating magnetic field with non-right flip angles. These results suggest that the partial spinlock sequence is a promising modality for functional connectivity measurements.
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Affiliation(s)
- Yosuke Ito
- Department of Electrical Engineering, Graduate School of Engineering, Kyoto University, Kyoto-Daigaku-Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan.
| | - Masahito Ueno
- Department of Electrical Engineering, Graduate School of Engineering, Kyoto University, Kyoto-Daigaku-Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan
| | - Tetsuo Kobayashi
- Department of Electrical Engineering, Graduate School of Engineering, Kyoto University, Kyoto-Daigaku-Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan
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11
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Mohammadi M, Silletta EV, Ilott AJ, Jerschow A. Diagnosing current distributions in batteries with magnetic resonance imaging. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 309:106601. [PMID: 31574355 DOI: 10.1016/j.jmr.2019.106601] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 09/09/2019] [Accepted: 09/15/2019] [Indexed: 06/10/2023]
Abstract
Batteries and their defects are notoriously difficult to analyze non-destructively, and consequently, many defects and failures remain little noticed and characterized until they cause grave damage. The measurement of the current density distributions inside a battery could reveal information about deviations from ideal cell behavior, and could thus provide early signs of deterioration or failures. Here, we describe methodology for fast nondestructive assessment and visualization of the effects of current distributions inside Li-ion pouch cells. The technique, based on magnetic resonance imaging (MRI), allows measuring magnetic field maps during charging/discharging. Marked changes in the distributions are observed as a function of the state of charge, and also upon sustaining damage. In particular, it is shown that nonlinearities and asymmetries of current distributions could be mapped at different charge states. Furthermore, hotspots of current flow are also shown to correlate with hotspots in charge storage. This technique could potentially be of great utility in diagnosing the health of cells and their behavior under different charging or environmental conditions.
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Affiliation(s)
- Mohaddese Mohammadi
- Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003, USA
| | - Emilia V Silletta
- Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003, USA
| | - Andrew J Ilott
- Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003, USA
| | - Alexej Jerschow
- Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003, USA.
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12
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Truong TK, Roberts KC, Woldorff MG, Song AW. Toward direct MRI of neuro-electro-magnetic oscillations in the human brain. Magn Reson Med 2019; 81:3462-3475. [PMID: 30652351 DOI: 10.1002/mrm.27654] [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] [Received: 06/14/2018] [Revised: 11/12/2018] [Accepted: 12/13/2018] [Indexed: 11/07/2022]
Abstract
PURPOSE Neuroimaging techniques are widely used to investigate the function of the human brain, but none are currently able to accurately localize neuronal activity with both high spatial and temporal specificity. Here, a new in vivo MRI acquisition and analysis technique based on the spin-lock mechanism is developed to noninvasively image local magnetic field oscillations resulting from neuroelectric activity in specifiable frequency bands. METHODS Simulations, phantom experiments, and in vivo experiments using an eyes-open/eyes-closed task in 8 healthy volunteers were performed to demonstrate its sensitivity and specificity for detecting oscillatory neuroelectric activity in the alpha-band (8-12 Hz). A comprehensive postprocessing procedure was designed to enhance the neuroelectric signal, while minimizing any residual hemodynamic and physiological confounds. RESULTS The phantom results show that this technique can detect 0.06-nT magnetic field oscillations, while the in vivo results demonstrate that it can image task-based modulations of neuroelectric oscillatory activity in the alpha-band. Multiple control experiments and a comparison with conventional BOLD functional MRI suggest that the activation was likely not due to any residual hemodynamic or physiological confounds. CONCLUSION These initial results provide evidence suggesting that this new technique has the potential to noninvasively and directly image neuroelectric activity in the human brain in vivo. With further development, this approach offers the promise of being able to do so with a combination of spatial and temporal specificity that is beyond what can be achieved with existing neuroimaging methods, which can advance our ability to study the functions and dysfunctions of the human brain.
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Affiliation(s)
- Trong-Kha Truong
- Brain Imaging and Analysis Center, Duke University, Durham, North Carolina
| | - Kenneth C Roberts
- Center for Cognitive Neuroscience, Duke University, Durham, North Carolina
| | - Marty G Woldorff
- Center for Cognitive Neuroscience, Duke University, Durham, North Carolina
| | - Allen W Song
- Brain Imaging and Analysis Center, Duke University, Durham, North Carolina
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13
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Chai Y, Sheng J, Men W, Fan Y, Wu B, Gao JH. MR imaging of oscillatory magnetic field changes: Progressing from phantom to human. Magn Reson Imaging 2016; 36:167-174. [PMID: 27826081 DOI: 10.1016/j.mri.2016.11.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 11/02/2016] [Indexed: 11/17/2022]
Abstract
Detection of ultra-weak oscillatory magnetic field changes using MRI is of great research interest not only for neuronal current MRI of endogenous neuronal oscillations but also for direct visualization of exogenous transcranial currents or iron oxide contrast agent distribution. In this work, we present a novel oscillatory-selective detection (OSD) method that is magnitude-sensitive to the oscillatory magnetic field changes and immune to the main field inhomogeneity. In OSD, a train of 180° pulses with alternating polarity and mirror symmetry are used to refocus and accumulate magnetization changes induced by external oscillatory fields. After taking both the signal change and image signal-to-noise ratio (SNR) into account, a final 90° pulse with a phase offset of 45° is applied to store a combination of the current-induced signal change and background magnetization for the subsequent EPI acquisition. Its performance was demonstrated in phantom and human studies, both of which showed much better detection in the comparison with the recently proposed spin-lock oscillatory excitation (SLOE) method. OSD was further successfully applied in imaging transcranial alternating current stimulation (tACS) induced field changes in the human brain. These promising results suggest that OSD can overcome the limitation of field inhomogeneity impeding previous oscillatory current MRI sensitivity and be a viable tool in future tACS study.
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Affiliation(s)
- Yuhui Chai
- Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China; Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Jingwei Sheng
- Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China; Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Weiwei Men
- Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China; Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Yang Fan
- GE Healthcare MR Research China, Beijing, China
| | - Bing Wu
- GE Healthcare MR Research China, Beijing, China
| | - Jia-Hong Gao
- Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China; Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China; McGovern Institute for Brain Research, Peking University, Beijing, China.
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14
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Elsayed HH, Mostafa AM, Soliman S, El-Bawab HY, Moharram AA, El-Nori AA. A magnet built on bronchoscopic suction for extraction of tracheobronchial headscarf pins: a novel technique and review of a tertiary centre experience. Interact Cardiovasc Thorac Surg 2016; 22:531-6. [PMID: 26850113 DOI: 10.1093/icvts/ivw006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 11/02/2015] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES Airway metal pins are one of the most commonly inhaled foreign bodies in Eastern societies in young females wearing headscarves. We innovated a modified bronchoscopic technique to extract tracheobronchial headscarf pins by the insertion of a magnet to allow an easy and non-traumatic extraction of the pins. The aim of this study was to assess the feasibility and safety of our new technique and compare it with our large previous experience with the classic bronchoscopic method of extraction of tracheobronchial headscarf pins. METHODS We performed a study comparing our retrospective experience of classic bronchoscopic extraction from February 2004 to January 2014 and prospective experience with our modified technique using the magnet from January 2014 to June 2015. An institutional review board and new device approval were obtained. RESULTS Three hundred and twenty-six procedures on 315 patients were performed during our initial 10-year experience. Of them, 304 patients were females. The median age of our group was 13 (0-62). The median time from inhalation to procedure was 1 day (0-1022). After introducing our modified new technique using the magnet, 20 procedures were performed. Nineteen were females. The median time of the procedure and the need to forcefully bend the pin for extraction were in favour of the new technique in comparison with our classic approach (2 vs 6 min; P < 0.001) (2 patients = 20% vs 192 = 58%; P < 0.001). The conversion rate to surgery was also in favour of the modified technique but did not reach statistical significance (0 = 0% vs 15 = 4.8%; P = 0.32). All patients who underwent the modified technique were discharged home on the same day of the procedure. No procedural complications were recorded. All remain well on a follow-up period of up to 14 months. CONCLUSIONS Bronchoscopic extraction of tracheobronchial inhaled headscarf pins using a novel technique using homemade magnets was safer and simpler in comparison with our large experience with the classic approach. We advise the use of this device (or concept) in selected patients in centres dealing with this problem.
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Affiliation(s)
- Hany H Elsayed
- Department of Thoracic Surgery, Ain Shams University, Cairo, Egypt
| | - Ahmed M Mostafa
- Department of Thoracic Surgery, Ain Shams University, Cairo, Egypt
| | - Saleh Soliman
- Department of Thoracic Surgery, Ain Shams University, Cairo, Egypt
| | - Hatem Y El-Bawab
- Department of Thoracic Surgery, Ain Shams University, Cairo, Egypt
| | - Adel A Moharram
- Department of Medical Engineering, Cairo University, Cairo, Egypt
| | - Ahmed A El-Nori
- Department of Thoracic Surgery, Ain Shams University, Cairo, Egypt
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15
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Kiefer C, Abela E, Schindler K, Wiest R. Focal Epilepsy: MR Imaging of Nonhemodynamic Field Effects by Using a Phase-cycled Stimulus-induced Rotary Saturation Approach with Spin-Lock Preparation. Radiology 2016; 280:237-43. [PMID: 26824710 DOI: 10.1148/radiol.2016150368] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Purpose To investigate whether nonhemodynamic resonant saturation effects can be detected in patients with focal epilepsy by using a phase-cycled stimulus-induced rotary saturation (PC-SIRS) approach with spin-lock (SL) preparation and whether they colocalize with the seizure onset zone and surface interictal epileptiform discharges (IED). Materials and Methods The study was approved by the local ethics committee, and all subjects gave written informed consent. Eight patients with focal epilepsy undergoing presurgical surface and intracranial electroencephalography (EEG) underwent magnetic resonance (MR) imaging at 3 T with a whole-brain PC-SIRS imaging sequence with alternating SL-on and SL-off and two-dimensional echo-planar readout. The power of the SL radiofrequency pulse was set to 120 Hz to sensitize the sequence to high gamma oscillations present in epileptogenic tissue. Phase cycling was applied to capture distributed current orientations. Voxel-wise subtraction of SL-off from SL-on images enabled the separation of T2* effects from rotary saturation effects. The topography of PC-SIRS effects was compared with the seizure onset zone at intracranial EEG and with surface IED-related potentials. Bayesian statistics were used to test whether prior PC-SIRS information could improve IED source reconstruction. Results Nonhemodynamic resonant saturation effects ipsilateral to the seizure onset zone were detected in six of eight patients (concordance rate, 0.75; 95% confidence interval: 0.40, 0.94) by means of the PC-SIRS technique. They were concordant with IED surface negativity in seven of eight patients (0.88; 95% confidence interval: 0.51, 1.00). Including PC-SIRS as prior information improved the evidence of the standard EEG source models compared with the use of uninformed reconstructions (exceedance probability, 0.77 vs 0.12; Wilcoxon test of model evidence, P < .05). Nonhemodynamic resonant saturation effects resolved in patients with favorable postsurgical outcomes, but persisted in patients with postsurgical seizure recurrence. Conclusion Nonhemodynamic resonant saturation effects are detectable during interictal periods with the PC-SIRS approach in patients with epilepsy. The method may be useful for MR imaging-based detection of neuronal currents in a clinical environment. (©) RSNA, 2016 Online supplemental material is available for this article.
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Affiliation(s)
- Claus Kiefer
- From the Support Center for Advanced Neuroimaging (SCAN), Institute of Diagnostic and Interventional Neuroimaging (C.K., E.A., R.W.), and Department of Neurology (K.S.), University Hospital Inselspital and University of Bern, Freiburgstrasse 4, 3010 Bern, Switzerland
| | - Eugenio Abela
- From the Support Center for Advanced Neuroimaging (SCAN), Institute of Diagnostic and Interventional Neuroimaging (C.K., E.A., R.W.), and Department of Neurology (K.S.), University Hospital Inselspital and University of Bern, Freiburgstrasse 4, 3010 Bern, Switzerland
| | - Kaspar Schindler
- From the Support Center for Advanced Neuroimaging (SCAN), Institute of Diagnostic and Interventional Neuroimaging (C.K., E.A., R.W.), and Department of Neurology (K.S.), University Hospital Inselspital and University of Bern, Freiburgstrasse 4, 3010 Bern, Switzerland
| | - Roland Wiest
- From the Support Center for Advanced Neuroimaging (SCAN), Institute of Diagnostic and Interventional Neuroimaging (C.K., E.A., R.W.), and Department of Neurology (K.S.), University Hospital Inselspital and University of Bern, Freiburgstrasse 4, 3010 Bern, Switzerland
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16
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Sheng J, Liu Y, Chai Y, Tang W, Wu B, Gao JH. A comprehensive study of sensitivity in measuring oscillatory magnetic fields using rotary saturation pulse sequences. Magn Reson Imaging 2015; 34:326-33. [PMID: 26616004 DOI: 10.1016/j.mri.2015.11.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 11/02/2015] [Accepted: 11/17/2015] [Indexed: 11/16/2022]
Abstract
Detecting the oscillatory currents with a specific frequency distribution may have the potential to make neuronal current MRI (ncMRI) come true. The phase shift or dephasing induced by both positive and negative episodes of oscillatory neuronal currents is likely to be canceled out over the echo time in typical BOLD-contrast fMRI experiments. Based on the contrast of rotary saturation, both of the recently developed spin-locked oscillatory excitation (SLOE) and stimulus-induced rotary saturation (SIRS) pulse sequences have been demonstrated to be able to detect weak oscillatory magnetic fields in phantoms with 3T MR scanners. In this report, through Bloch equation simulation as well as water phantom and anesthetic rats experiments, we comprehensively evaluate and compare the sensitivities of these two methods (SLOE and SIRS) in detecting the oscillatory magnetic fields for both high (100 Hz) and low (10 Hz) oscillation frequencies, while using their respective optimal imaging parameters. In agreement with the theoretical predications, both the simulated and experimental results showed that the SLOE method features a much higher detection sensitivity of weak magnetic fields than that of the SIRS method. SLOE was able to detect applied oscillatory magnetic fields as low as 0.1 nT in a water phantom and 0.5 nT in rat brains and the deteriorated noise levels in rat data may account for the reduced sensitivity in vivo. These promising results form the foundation for direct detection of in vivo neuronal currents using MRI.
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Affiliation(s)
- Jingwei Sheng
- Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China; Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China
| | - Yun Liu
- Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China; Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China
| | - Yuhui Chai
- Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China; Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China
| | - Weinan Tang
- Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China; Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China; McGovern Institute for Brain Research, Peking University, Beijing, China
| | - Bing Wu
- GE Healthcare China, Beijing, China
| | - Jia-Hong Gao
- Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China; Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China; McGovern Institute for Brain Research, Peking University, Beijing, China.
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17
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Jiang X, Sheng J, Li H, Chai Y, Zhou X, Wu B, Guo X, Gao JH. Detection of subnanotesla oscillatory magnetic fields using MRI. Magn Reson Med 2015; 75:519-26. [PMID: 25753110 DOI: 10.1002/mrm.25553] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 10/14/2014] [Accepted: 11/07/2014] [Indexed: 11/09/2022]
Abstract
PURPOSE Direct mapping of neuronal currents using MRI would have fundamental impacts on brain functional imaging. Previous reports indicated that the stimulus-induced rotary saturation (SIRS) mechanism had the best potential of direct detection of neural oscillations; however, it lacked the high-sensitivity level needed. In this study, a novel strategy is proposed in an effort to improve the detection sensitivity. METHODS In our modified SIRS sequence, an external oscillatory magnetic field is used as the excitation pulse in place of the standard 90-degree excitation pulse. This approach could potentially lead to tens or even hundreds times of enhancement in the detection sensitivity for low field signals. It also helps to lower the physiological noise, allows for shorter pulse repetition time, and is less affected by the blood oxygen level. RESULTS We demonstrate that a 100-Hz oscillatory magnetic field with magnitude as low as 0.25 nanotesla generated in a current loop can be robustly detected using a 3-Tesla MRI scanner. CONCLUSION The modified SIRS sequence offers higher detection sensitivity as well as several additional advantages. These promising results suggest that the direct detection of neural oscillation might be within the grasp of the current MRI technology.
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Affiliation(s)
- Xia Jiang
- Brain Research Imaging Center, University of Chicago, Chicago, IL, 60637
| | - Jingwei Sheng
- Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.,Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China
| | - Huanjie Li
- Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.,Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China
| | - Yuhui Chai
- Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.,Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China
| | - Xin Zhou
- Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, China
| | - Bing Wu
- GE Healthcare MR Research China, Beijing, China
| | - Xiaodong Guo
- Brain Research Imaging Center, University of Chicago, Chicago, IL, 60637
| | - Jia-Hong Gao
- Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.,Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China.,McGovern Institute for Brain Research, Peking University, Beijing, China
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18
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Zhu B, Witzel T, Jiang S, Huang SY, Rosen BR, Wald LL. Selective magnetic resonance imaging of magnetic nanoparticles by acoustically induced rotary saturation. Magn Reson Med 2014; 75:97-106. [PMID: 25537578 DOI: 10.1002/mrm.25522] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2014] [Revised: 09/14/2014] [Accepted: 10/17/2014] [Indexed: 12/21/2022]
Abstract
PURPOSE The goal of this study was to introduce a new method to selectively detect iron oxide contrast agents using an acoustic wave to perturb the spin-locked water signal in the vicinity of the magnetic particles. The acoustic drive can be modulated externally to turn the effect on and off, allowing sensitive and quantitative statistical comparison and removal of confounding image background variations. METHODS We demonstrated the effect in spin-locking experiments using piezoelectric actuators to generate vibrational displacements of iron oxide samples. We observed a resonant behavior of the signal changes with respect to the acoustic frequency where iron oxide is present. We characterized the effect as a function of actuator displacement and contrast agent concentration. RESULTS The resonant effect allowed us to generate block-design "modulation response maps" indicating the contrast agent's location, as well as positive contrast images with suppressed background signal. We found that the acoustically induced rotary saturation (AIRS) effect stayed approximately constant across acoustic frequency and behaved monotonically over actuator displacement and contrast agent concentration. CONCLUSION AIRS is a promising method capable of using acoustic vibrations to modulate the contrast from iron oxide nanoparticles and thus perform selective detection of the contrast agents, potentially enabling more accurate visualization of contrast agents in clinical and research settings.
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Affiliation(s)
- Bo Zhu
- Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts, USA.,Harvard-MIT Division of Health Sciences Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Thomas Witzel
- Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts, USA
| | - Shan Jiang
- David H Koch Institute for Integrative Cancer Research, Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Susie Y Huang
- Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts, USA
| | - Bruce R Rosen
- Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts, USA.,Department of Meridian & Acupuncture, Collaborating Center for Traditional Medicine, East-West Medical Research Institute and School of Korean Medicine, Kyung Hee University, Seoul, Republic of Korea.,Harvard-MIT Division of Health Sciences Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Lawrence L Wald
- Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts, USA.,Harvard-MIT Division of Health Sciences Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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19
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Balasubramanian M, Mulkern RV, Wells WM, Sundaram P, Orbach DB. Magnetic resonance imaging of ionic currents in solution: the effect of magnetohydrodynamic flow. Magn Reson Med 2014; 74:1145-55. [PMID: 25273917 DOI: 10.1002/mrm.25445] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Revised: 07/25/2014] [Accepted: 08/15/2014] [Indexed: 11/06/2022]
Abstract
PURPOSE Reliably detecting MRI signals in the brain that are more tightly coupled to neural activity than blood-oxygen-level-dependent fMRI signals could not only prove valuable for basic scientific research but could also enhance clinical applications such as epilepsy presurgical mapping. This endeavor will likely benefit from an improved understanding of the behavior of ionic currents, the mediators of neural activity, in the presence of the strong magnetic fields that are typical of modern-day MRI scanners. THEORY Of the various mechanisms that have been proposed to explain the behavior of ionic volume currents in a magnetic field, only one-magnetohydrodynamic flow-predicts a slow evolution of signals, on the order of a minute for normal saline in a typical MRI scanner. METHODS This prediction was tested by scanning a volume-current phantom containing normal saline with gradient-echo-planar imaging at 3 T. RESULTS Greater signal changes were observed in the phase of the images than in the magnitude, with the changes evolving on the order of a minute. CONCLUSION These results provide experimental support for the MHD flow hypothesis. Furthermore, MHD-driven cerebrospinal fluid flow could provide a novel fMRI contrast mechanism.
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Affiliation(s)
- Mukund Balasubramanian
- Department of Radiology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Robert V Mulkern
- Department of Radiology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - William M Wells
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Padmavathi Sundaram
- Department of Radiology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Darren B Orbach
- Department of Radiology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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20
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Laakso I, Matsumoto H, Hirata A, Terao Y, Hanajima R, Ugawa Y. Multi-scale simulations predict responses to non-invasive nerve root stimulation. J Neural Eng 2014; 11:056013. [DOI: 10.1088/1741-2560/11/5/056013] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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21
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Marblestone AH, Zamft BM, Maguire YG, Shapiro MG, Cybulski TR, Glaser JI, Amodei D, Stranges PB, Kalhor R, Dalrymple DA, Seo D, Alon E, Maharbiz MM, Carmena JM, Rabaey JM, Boyden ES, Church GM, Kording KP. Physical principles for scalable neural recording. Front Comput Neurosci 2013; 7:137. [PMID: 24187539 PMCID: PMC3807567 DOI: 10.3389/fncom.2013.00137] [Citation(s) in RCA: 134] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2013] [Accepted: 09/23/2013] [Indexed: 12/20/2022] Open
Abstract
Simultaneously measuring the activities of all neurons in a mammalian brain at millisecond resolution is a challenge beyond the limits of existing techniques in neuroscience. Entirely new approaches may be required, motivating an analysis of the fundamental physical constraints on the problem. We outline the physical principles governing brain activity mapping using optical, electrical, magnetic resonance, and molecular modalities of neural recording. Focusing on the mouse brain, we analyze the scalability of each method, concentrating on the limitations imposed by spatiotemporal resolution, energy dissipation, and volume displacement. Based on this analysis, all existing approaches require orders of magnitude improvement in key parameters. Electrical recording is limited by the low multiplexing capacity of electrodes and their lack of intrinsic spatial resolution, optical methods are constrained by the scattering of visible light in brain tissue, magnetic resonance is hindered by the diffusion and relaxation timescales of water protons, and the implementation of molecular recording is complicated by the stochastic kinetics of enzymes. Understanding the physical limits of brain activity mapping may provide insight into opportunities for novel solutions. For example, unconventional methods for delivering electrodes may enable unprecedented numbers of recording sites, embedded optical devices could allow optical detectors to be placed within a few scattering lengths of the measured neurons, and new classes of molecularly engineered sensors might obviate cumbersome hardware architectures. We also study the physics of powering and communicating with microscale devices embedded in brain tissue and find that, while radio-frequency electromagnetic data transmission suffers from a severe power-bandwidth tradeoff, communication via infrared light or ultrasound may allow high data rates due to the possibility of spatial multiplexing. The use of embedded local recording and wireless data transmission would only be viable, however, given major improvements to the power efficiency of microelectronic devices.
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Affiliation(s)
- Adam H. Marblestone
- Biophysics Program, Harvard UniversityBoston, MA, USA
- Wyss Institute for Biologically Inspired Engineering at Harvard UniversityBoston, MA, USA
| | | | - Yael G. Maguire
- Department of Genetics, Harvard Medical SchoolBoston, MA, USA
- Plum Labs LLCCambridge, MA, USA
| | - Mikhail G. Shapiro
- Division of Chemistry and Chemical Engineering, California Institute of TechnologyPasadena, CA, USA
| | | | - Joshua I. Glaser
- Interdepartmental Neuroscience Program, Northwestern UniversityChicago, IL, USA
| | - Dario Amodei
- Department of Radiology, Stanford UniversityPalo Alto, CA, USA
| | | | - Reza Kalhor
- Department of Genetics, Harvard Medical SchoolBoston, MA, USA
| | - David A. Dalrymple
- Biophysics Program, Harvard UniversityBoston, MA, USA
- NemaloadSan Francisco, CA, USA
- Media Laboratory, Massachusetts Institute of TechnologyCambridge, MA, USA
| | - Dongjin Seo
- Department of Electrical Engineering and Computer Sciences, University of California at BerkeleyBerkeley, CA, USA
| | - Elad Alon
- Department of Electrical Engineering and Computer Sciences, University of California at BerkeleyBerkeley, CA, USA
| | - Michel M. Maharbiz
- Department of Electrical Engineering and Computer Sciences, University of California at BerkeleyBerkeley, CA, USA
| | - Jose M. Carmena
- Department of Electrical Engineering and Computer Sciences, University of California at BerkeleyBerkeley, CA, USA
- Helen Wills Neuroscience Institute, University of California at BerkeleyBerkeley, CA, USA
| | - Jan M. Rabaey
- Department of Electrical Engineering and Computer Sciences, University of California at BerkeleyBerkeley, CA, USA
| | - Edward S. Boyden
- Media Laboratory, Massachusetts Institute of TechnologyCambridge, MA, USA
- Departments of Brain and Cognitive Sciences and Biological Engineering, Massachusetts Institute of TechnologyCambridge, MA, USA
| | - George M. Church
- Biophysics Program, Harvard UniversityBoston, MA, USA
- Wyss Institute for Biologically Inspired Engineering at Harvard UniversityBoston, MA, USA
- Department of Genetics, Harvard Medical SchoolBoston, MA, USA
| | - Konrad P. Kording
- Departments of Physical Medicine and Rehabilitation and of Physiology, Northwestern University Feinberg School of MedicineChicago, IL, USA
- Sensory Motor Performance Program, The Rehabilitation Institute of ChicagoChicago, IL, USA
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22
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Hernandez-Garcia L, Bhatia V, Prem-Kumar K, Ulfarsson M. Magnetic resonance imaging of time-varying magnetic fields from therapeutic devices. NMR IN BIOMEDICINE 2013; 26:718-724. [PMID: 23355446 PMCID: PMC3645268 DOI: 10.1002/nbm.2919] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Revised: 11/26/2012] [Accepted: 12/16/2012] [Indexed: 06/01/2023]
Abstract
While magnetic resonance imaging of static magnetic fields generated by external probes has been previously demonstrated, there is an unmet need to image time-varying magnetic fields such as those generated by transcranial magnetic stimulators and radiofrequency hyperthermia probes. A method to image such time-varying magnetic fields is introduced in this study. This article presents the theory behind the method and provides proof of concept by imaging time-varying magnetic fields generated by a figure-eight coil inside simple phantoms over a range of frequencies and intensities using a 7T small animal MRI scanner. The method was able to reconstruct the three-dimensional components of the oscillating magnetic field vector.
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Nagahara S, Kobayashi T. Bloch simulations towards direct detection of oscillating magnetic fields using MRI with spin-lock sequence. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2013; 2013:1061-1064. [PMID: 24109874 DOI: 10.1109/embc.2013.6609687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A new MRI method using the spin-lock sequence has attracted wide attention because of its potential for detecting small oscillating magnetic fields. However, as the mechanism involved is complicated, we visualized the magnetization performance during the spin-lock sequence in order to better understand interaction of the spin-lock pulse and the externally applied oscillating magnetic fields by means of a fast-and-simple method using matrix operations to solve a time-dependent Bloch equation. To improve spin-lock imaging in the detection of small magnetic fields (in an fMRI experiment that modeled neural magnetic fields), we observed that the phenomenon decreases MR signals, which led us to investigate how spin-lock parameters cause the MR signal to decrease; based on this, we determined that MR signals decrease in oscillating magnetic fields that are resonant with the spin-lock pulse. We also determined that MR signals decrease is directly proportional to spin-lock duration. Our results suggest that MRI can feasibly detect oscillating magnetic fields directly by using of the spin-lock sequence.
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NAGAHARA S, UENO M, KOBAYASHI T. Spin-Lock Imaging for Direct Detection of Oscillating Magnetic Fields with MRI: Simulations and Phantom Studies. ADVANCED BIOMEDICAL ENGINEERING 2013. [DOI: 10.14326/abe.2.63] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Affiliation(s)
- Shizue NAGAHARA
- Department of Electrical Engineering, Graduate School of Engineering, Kyoto University
- Research Fellow of the Japan Society for the Promotion of Science
| | - Masahito UENO
- Department of Electrical Engineering, Graduate School of Engineering, Kyoto University
| | - Tetsuo KOBAYASHI
- Department of Electrical Engineering, Graduate School of Engineering, Kyoto University
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25
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De Luca F. Direct fMRI by random spin-lock along the neural field. Magn Reson Imaging 2011; 29:951-7. [DOI: 10.1016/j.mri.2011.04.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Revised: 03/29/2011] [Accepted: 04/03/2011] [Indexed: 10/18/2022]
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