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Zhu H, Lang ML, Yang Y, Martin M, Zhang G, Zhang Q, Chen Y, Yan X. Detunable wireless Litzcage coil for human head MRI at 1.5 T. NMR IN BIOMEDICINE 2024; 37:e5068. [PMID: 37964107 DOI: 10.1002/nbm.5068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 10/09/2023] [Accepted: 10/11/2023] [Indexed: 11/16/2023]
Abstract
Inductively coupled radiofrequency (RF) coils are an inexpensive and simple method to realize wireless RF coils in magnetic resonance imaging (MRI), which can significantly ease the MRI scan setup and improve patient comfort because they do not require bulky components such as cables, baluns, preamplifiers, and connectors. However, volume-type wireless coils are typically operated in transmit/receive mode because detuning such coils is much more challenging due to their complex structure and multiple resonant modes. Meanwhile, adding too many detuning circuits to a wireless coil would decrease the coil's quality factor, impair the signal-to-noise ratio, and increase the cost. In this work, we proposed, constructed, and tested a novel wireless volume coil based on the Litzcage design for 1.5-T head imaging. Being an inductively coupled coil, it has a much simpler structure, resulting in a lighter weight and less bulky design. Despite its simpler structure, it exhibits comparable imaging performance with a commercial receive array, providing an alternative to conventional wired coils with a high cost and complex structure. The unique figure-of-8 conductor pattern within the rungs ensures that the proposed wireless Litzcage can be efficiently detuned with minimal detuning circuits.
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Affiliation(s)
- Haoqin Zhu
- Sino Canada Health Institute Inc., Winnipeg, Manitoba, Canada
| | - Michael L Lang
- Sino Canada Health Institute Inc., Winnipeg, Manitoba, Canada
- Department of Physics, The University of Winnipeg, Winnipeg, Manitoba, Canada
| | - Yijin Yang
- Department of Electrical and Computer Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Melanie Martin
- Department of Physics, The University of Winnipeg, Winnipeg, Manitoba, Canada
| | - Gong Zhang
- Hubei Key Laboratory of Intelligent Conveying Technology and Device, Hubei Polytechnic University, Huangshi, China
| | - Qiang Zhang
- The Affiliated Hospital of Inner Mongolia Medical University, Hohhot, China
| | - Yuanyuan Chen
- Sino Canada Health Engineering Research Institute (Hefei) Ltd., Hefei, Anhui, China
| | - Xinqiang Yan
- Department of Electrical and Computer Engineering, Vanderbilt University, Nashville, Tennessee, USA
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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Chen Y, Wang Q, Choi S, Zeng H, Takahashi K, Qian C, Yu X. Focal fMRI signal enhancement with implantable inductively coupled detectors. Neuroimage 2022; 247:118793. [PMID: 34896291 PMCID: PMC8842502 DOI: 10.1016/j.neuroimage.2021.118793] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2021] [Revised: 12/02/2021] [Accepted: 12/07/2021] [Indexed: 12/16/2022] Open
Abstract
Despite extensive efforts to increase the signal-to-noise ratio (SNR) of fMRI images for brain-wide mapping, technical advances of focal brain signal enhancement are lacking, in particular, for animal brain imaging. Emerging studies have combined fMRI with fiber optic-based optogenetics to decipher circuit-specific neuromodulation from meso to macroscales. High-resolution fMRI is needed to integrate hemodynamic responses into cross-scale functional dynamics, but the SNR remains a limiting factor given the complex implantation setup of animal brains. Here, we developed a multimodal fMRI imaging platform with an implanted inductive coil detector. This detector boosts the tSNR of MRI images, showing a 2-3-fold sensitivity gain over conventional coil configuration. In contrast to the cryoprobe or array coils with limited spaces for implanted brain interface, this setup offers a unique advantage to study brain circuit connectivity with optogenetic stimulation and can be further extended to other multimodal fMRI mapping schemes.
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Affiliation(s)
- Yi Chen
- Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany; Max Planck Institute for the Science of Light, 91058, Erlangen, Germany
| | - Qi Wang
- Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany; Graduate Training Centre of Neuroscience, University of Tuebingen, 72076 Tuebingen, Germany
| | - Sangcheon Choi
- Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany; Graduate Training Centre of Neuroscience, University of Tuebingen, 72076 Tuebingen, Germany
| | - Hang Zeng
- Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany; Graduate Training Centre of Neuroscience, University of Tuebingen, 72076 Tuebingen, Germany
| | - Kengo Takahashi
- Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany; Graduate Training Centre of Neuroscience, University of Tuebingen, 72076 Tuebingen, Germany
| | - Chunqi Qian
- Department of Radiology, Michigan State University, East Lansing, MI 48824, USA.
| | - Xin Yu
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA.
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Gulyaev MV, Pavlova OS, Volkov DV, Sadykhov EG, Anisimov NV, Pirogov YA. Application of copper plates for frequency tuning of surface wired and wireless MRI coils. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 309:106626. [PMID: 31678914 DOI: 10.1016/j.jmr.2019.106626] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 10/14/2019] [Accepted: 10/23/2019] [Indexed: 05/27/2023]
Abstract
This study shows how a copper plate could be used for frequency tuning of surface wired and wireless MRI coils. For this purpose, it is proposed to place the copper plate directly on their conducting circuit. This leads to increase in the resonance frequency of coils. The effect is most perceptible if the copper plate is comparable in size to the conducting circuit of radiofrequency (RF) coil. The experimental work was performed on a 7.05 T MR scanner using surface MRI coils operating on different resonance frequencies: 1H (300 MHz), 31P (121 MHz), 23Na (79 MHz), 13C (75 MHz). Application of copper plate for frequency tuning of wireless multi-turn multi-gap transmission line resonator (MTMG-TLR) was considered for the first time. The proposed method can be claimed if the nominal variable inductance or capacitance is not enough for tuning the resonance frequency of the MRI coil to a higher frequency range.
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Affiliation(s)
| | - Olga S Pavlova
- Lomonosov Moscow State University, Moscow 119991, Russia.
| | | | - Elnur G Sadykhov
- National Research Nuclear University "MEPhI", Moscow 115409, Russia
| | | | - Yury A Pirogov
- Lomonosov Moscow State University, Moscow 119991, Russia; National Research Nuclear University "MEPhI", Moscow 115409, Russia
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Jouda M, Kamberger R, Leupold J, Spengler N, Hennig J, Gruschke O, Korvink JG. A comparison of Lenz lenses and LC resonators for NMR signal enhancement. CONCEPTS IN MAGNETIC RESONANCE. PART B, MAGNETIC RESONANCE ENGINEERING 2017; 47B:e21357. [PMID: 29541005 PMCID: PMC5839471 DOI: 10.1002/cmr.b.21357] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 09/11/2017] [Accepted: 10/26/2017] [Indexed: 06/09/2023]
Abstract
High signal-to-noise ratio (SNR) of the NMR signal has always been a key target that drives massive research effort in many fields. Among several parameters, a high filling factor of the MR coil has proven to boost the SNR. In case of small-volume samples, a high filling factor and thus a high SNR can be achieved through miniaturizing the MR coil. However, under certain circumstances, this can be impractical. In this paper, we present an extensive theoretical and experimental investigation of the inductively coupled LC resonator and the magnetic Lenz lens as two candidate approaches that can enhance the SNR in such circumstances. The results demonstrate that the narrow-band LC resonator is superior in terms of SNR, while the non-tuned nature of the Lenz lens makes it preferable in broadband applications.
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Affiliation(s)
- Mazin Jouda
- Karlsruhe Institute of Technology‐KITInstitute of Microstructure Technology‐IMTEggenstein‐LeopoldshafenGermany
| | - Robert Kamberger
- BrainLinks‐BrainTools Cluster of ExcellenceInstitute of Microsystems Technology‐IMTEKUniversity of FreiburgFreiburgGermany
| | - Jochen Leupold
- Department of RadiologyMedical PhysicsMedical Center ‐ University of FreiburgFaculty of MedicineUniversity of FreiburgFreiburgGermany
| | | | - Jürgen Hennig
- Department of RadiologyMedical PhysicsMedical Center ‐ University of FreiburgFaculty of MedicineUniversity of FreiburgFreiburgGermany
| | | | - Jan G. Korvink
- Karlsruhe Institute of Technology‐KITInstitute of Microstructure Technology‐IMTEggenstein‐LeopoldshafenGermany
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Mett RR, Sidabras JW, Hyde JS. MRI surface-coil pair with strong inductive coupling. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:124704. [PMID: 28040909 PMCID: PMC5201604 DOI: 10.1063/1.4972391] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 12/04/2016] [Indexed: 05/31/2023]
Abstract
A novel inductively coupled coil pair was used to obtain magnetic resonance phantom images. Rationale for using such a structure is described in R. R. Mett et al. [Rev. Sci. Instrum. 87, 084703 (2016)]. The original rationale was to increase the Q-value of a small diameter surface coil in order to achieve dominant loading by the sample. A significant improvement in the vector reception field (VRF) is also seen. The coil assembly consists of a 3-turn 10 mm tall meta-metallic self-resonant spiral (SRS) of inner diameter 10.4 mm and outer diameter 15.1 mm and a single-loop equalization coil of 25 mm diameter and 2 mm tall. The low-frequency parallel mode was used in which the rf currents on each coil produce magnetic fields that add constructively. The SRS coil assembly was fabricated and data were collected using a tissue-equivalent 30% polyacrylamide phantom. The large inductive coupling of the coils produces phase-coherency of the rf currents and magnetic fields. Finite-element simulations indicate that the VRF of the coil pair is about 4.4 times larger than for a single-loop coil of 15 mm diameter. The mutual coupling between coils influences the current ratio between the coils, which in turn influences the VRF and the signal-to-noise ratio (SNR). Data on a tissue-equivalent phantom at 9.4 T show a total SNR increase of 8.8 over the 15 mm loop averaged over a 25 mm depth and diameter. The experimental results are shown to be consistent with the magnetic resonance theory of the emf induced by spins in a coil, the theory of inductively coupled resonant circuits, and the superposition principle. The methods are general for magnetic resonance and other types of signal detection and can be used over a wide range of operating frequencies.
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Affiliation(s)
- Richard R Mett
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
| | - Jason W Sidabras
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
| | - James S Hyde
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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Ginefri JC, Rubin A, Tatoulian M, Woytasik M, Boumezbeur F, Djemaï B, Poirier-Quinot M, Lethimonnier F, Darrasse L, Dufour-Gergam E. Implanted, inductively-coupled, radiofrequency coils fabricated on flexible polymeric material: application to in vivo rat brain MRI at 7 T. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 224:61-70. [PMID: 23041797 DOI: 10.1016/j.jmr.2012.09.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Revised: 09/01/2012] [Accepted: 09/09/2012] [Indexed: 06/01/2023]
Abstract
Combined with high-field MRI scanners, small implanted coils allow for high resolution imaging with locally improved SNR, as compared to external coils. Small flexible implantable coils dedicated to in vivo MRI of the rat brain at 7 T were developed. Based on the Multi-turn Transmission Line Resonator design, they were fabricated with a Teflon substrate using copper micromolding process and a specific metal-polymer adhesion treatment. The implanted coils were made biocompatible by PolyDimethylSiloxane (PDMS) encapsulation. The use of low loss tangent material achieves low dielectric losses within the substrate and the use of the PDMS layer reduces the parasitic coupling with the surrounding media. An implanted coil was implemented in a 7 T MRI system using inductive coupling and a dedicated external pick-up coil for signal transmission. In vivo images of the rat brain acquired with in plane resolution of (150 μm)(2) thanks to the implanted coil revealed high SNR near the coil, allowing for the visualization of fine cerebral structures.
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Affiliation(s)
- J-C Ginefri
- IR4M, Université Paris-Sud, UMR8081, F-91405 Orsay, France.
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Takeda K. Microcoils and microsamples in solid-state NMR. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2012; 47-48:1-9. [PMID: 23083521 DOI: 10.1016/j.ssnmr.2012.09.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Revised: 09/13/2012] [Accepted: 09/14/2012] [Indexed: 06/01/2023]
Abstract
Recent reports on microcoils are reviewed. The first part of the review includes a discussion of how the geometries of the sample and coil affect the NMR signal intensity. In addition to derivation of the well-known result that the signal intensity increases as the coil size decreases, the prediction that dilution of a small sample with magnetically inert matter leads to better sensitivity if a tiny coil is not available is given. The second part of the review focuses on the issues specific to solid-state NMR. They include realization of magic-angle spinning (MAS) using a microcoil and harnessing of such strong pulses that are feasible only with a microcoil. Two strategies for microcoil MAS, the piggyback method and magic-angle coil spinning (MACS), are reviewed. In addition, MAS of flat, disk-shaped samples is discussed in the context of solid-state NMR of small-volume samples. Strong RF irradiation, which has been exploited in wide-line spectral excitation, multiple-quantum MAS (MQMAS), and dipolar decoupling experiments, has been accompanied by new challenges regarding the Bloch-Siegert effect, the minimum time resolution of the spectrometer, and the time scale of pulse transient effects. For a possible solution to the latter problem, recent reports on active compensation of pulse transients are described.
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Affiliation(s)
- Kazuyuki Takeda
- Division of Chemistry, Graduate School of Science, Kyoto University, 606-8502 Kyoto, Japan.
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Fabrication and Packaging of Flexible Polymeric Microantennae for in Vivo Magnetic Resonance Imaging. Polymers (Basel) 2012. [DOI: 10.3390/polym4010656] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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