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Liu J, Wang M, Sun Z, Wang Y, Yang G, Wang W, Wang Q. Method for determining matching capacitances for floating cable traps in magnetic resonance imaging up to 14 T. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2024; 358:107612. [PMID: 38118321 DOI: 10.1016/j.jmr.2023.107612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2023] [Revised: 12/07/2023] [Accepted: 12/12/2023] [Indexed: 12/22/2023]
Abstract
Floating cable traps (FCTs) enhance coil tuning, improve the signal-to-noise ratio of magnetic resonance imaging (MRI), and reduce the risks to patients. As MRI technology continues to advance, it becomes crucial to design efficient FCTs that are tailored to different magnetic fields and nuclei. Here, a method is proposed for determining and correcting the appropriate capacitances for FCTs in MRI systems. To validate the effectiveness of this approach, FCTs were designed and manufactured for hydrogen nuclei in magnetic fields of 1.5-14 T. The results of bench testing show that the attenuation of common-mode currents was more than -20 dB, and the maximum frequency deviation in all the FCTs was 0.345%. Furthermore, the results of magnetic resonance spin-echo imaging show that the signal-to-noise ratio was improved significantly by using the FCTs. Overall, this study shows the effectiveness of the designed FCTs in improving signal-to-noise ratio, and it provides valuable insights for designing efficient FCTs tailored to different magnetic fields and nuclei in MRI applications.
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Affiliation(s)
- Jinhao Liu
- School of Electrical Engineering, Xi'an Jiaotong University, Xi'an, 710049, China.
| | - Miutian Wang
- School of Electronics, Peking University, Beijing, 100871, China.
| | - Zhen Sun
- School of Electronics, Peking University, Beijing, 100871, China.
| | - Yaohui Wang
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing, 100190, China; Division of Superconducting Magnet Science and Technology, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, 100190, China.
| | - Gang Yang
- Institute of Biomedical Engineering, Peking University Shenzhen Graduate School, Shenzhen, 518055, China.
| | - Weimin Wang
- School of Electronics, Peking University, Beijing, 100871, China; Institute of Biomedical Engineering, Peking University Shenzhen Graduate School, Shenzhen, 518055, China; Institute of Biomedical Engineering, Shenzhen Bay Laboratory, Shenzhen, 518132, China.
| | - Qiuliang Wang
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing, 100190, China; Division of Superconducting Magnet Science and Technology, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, 100190, China.
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Chai S, Yan X. Miniature and flexible Bazooka balun for high-field MRI. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 356:107577. [PMID: 37897924 PMCID: PMC10842505 DOI: 10.1016/j.jmr.2023.107577] [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: 05/18/2023] [Revised: 10/10/2023] [Accepted: 10/23/2023] [Indexed: 10/30/2023]
Abstract
Flexible coils offer improved patient comfort and better imaging quality. However, rigid and bulky baluns in RF coils limit flexibility and manufacturing. A miniaturized and flexible balun design was proposed to address this issue. It replaced rigid components with an ultra-flexible rubber tube and a flexible coaxial capacitor. Simulations validated the concept, and bench tests confirmed its performance, including a measured common-mode rejection ratio of -15.8 dB. The flexible balun was integrated into a 4-channel coil array, evaluating impedance changes caused by the "hand effect." Compared to coils without the balun, the flexible coil with the proposed balun showed improved robustness in impedance matching and inter-element couplings. Transmit efficiency of the flexible coil with the balun was compared to coils without a balun and with a rigid, shielded cable trap. Results demonstrated that the proposed balun circuit maintained high transmit efficiency. Overall, the flexible balun design offers a promising solution for improving the flexibility and performance of RF coil arrays in MRI applications.
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Affiliation(s)
- Shuyang Chai
- Department of Electrical and Computer Engineering, Vanderbilt University, Nashville, TN 37232, USA; Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Xinqiang Yan
- Department of Electrical and Computer Engineering, Vanderbilt University, Nashville, TN 37232, USA; Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
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Karasan E, Hammerschmidt A, Arias AC, Taracila V, Robb F, Lustig M. Caterpillar traps: A highly flexible, distributed system of toroidal cable traps. Magn Reson Med 2023; 89:2471-2484. [PMID: 36695296 PMCID: PMC10278796 DOI: 10.1002/mrm.29584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 12/05/2022] [Accepted: 12/29/2022] [Indexed: 01/26/2023]
Abstract
PURPOSE Coil arrays are connected to the main MRI system with long, shielded coaxial cables. RF coupling of these cables to the main transmit coil can cause high shield currents, which pose risks of heating and RF burns. High-blocking resonant RF traps are placed at distinct positions along cables to mitigate these currents. Traditional traps are designed to be stiff to avoid changes in their resonant frequency, hindering the overall system flexibility. Instead of using a few high-blocking traps, we propose the use of caterpillar traps-a distributed system of small, elastic traps that cover the full length of cables. METHODS We leverage an array of resonant toroids as traps, forming a caterpillar-like structure whereby bending only impacts individual traps minimally. Benchtop measurements are used to determine the blocking of caterpillar traps and show their robustness to bending. We also compare an anterior array system cable covered with caterpillar traps to a commercial cable with B1 + and heating measurements. RESULTS Benchtop experiments with caterpillar traps demonstrate high robustness to bending. B1 + mapping experiments of an anterior array cable show improved blocking and flexibility compared to a commercial cable. CONCLUSION Caterpillar traps provide sufficient attenuation to shield currents while allowing cable flexibility. Our distributed design can provide high blocking efficiency at different positions and orientations, even in cases where commercial cable traps cannot.
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Affiliation(s)
- Ekin Karasan
- Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, USA
| | | | - Ana Claudia Arias
- Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, USA
| | | | | | - Michael Lustig
- Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, USA
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Winter L, Seifert F, Zilberti L, Murbach M, Ittermann B. MRI‐Related Heating of Implants and Devices: A Review. J Magn Reson Imaging 2020; 53:1646-1665. [DOI: 10.1002/jmri.27194] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 04/29/2020] [Accepted: 04/30/2020] [Indexed: 12/11/2022] Open
Affiliation(s)
- Lukas Winter
- Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany
| | - Frank Seifert
- Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany
| | - Luca Zilberti
- Istituto Nazionale di Ricerca Metrologica Torino Italy
| | - Manuel Murbach
- ZMT Zurich MedTech AG Zurich Switzerland
- Institute for Molecular Instrumentation and Imaging (i3M) Universidad Politécnica de Valencia (UPV) Valencia Spain
| | - Bernd Ittermann
- Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany
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Alipour A, Meyer ES, Dumoulin CL, Watkins RD, Elahi H, Loew W, Schweitzer J, Olson G, Chen Y, Tao S, Guttman M, Kolandaivelu A, Halperin HR, Schmidt EJ. MRI Conditional Actively Tracked Metallic Electrophysiology Catheters and Guidewires With Miniature Tethered Radio-Frequency Traps: Theory, Design, and Validation. IEEE Trans Biomed Eng 2019; 67:1616-1627. [PMID: 31535979 DOI: 10.1109/tbme.2019.2941460] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
OBJECTIVE Cardiovascular interventional devices typically have long metallic braids or backbones to aid in steerability and pushability. However, electromagnetic coupling of metallic-based cardiovascular interventional devices with the radiofrequency (RF) fields present during Magnetic Resonance Imaging (MRI) can make a device unsafe for use in an MRI scanner. We aimed to develop MRI conditional actively-tracked cardiovascular interventional devices by sufficiently attenuating induced currents on the metallic braid/tube and internal-cabling using miniaturized resonant floating RF traps (MBaluns). METHOD MBaluns were designed for placement at multiple locations along a conducting cardiovascular device to prevent the establishment of standing waves and to dissipate RF-induced energy. The MBaluns were constructed with loosely-wound solenoids to be sensitive to transverse magnetic fields created by both surface currents on the device's metallic backbone and common-mode currents on internal cables. Electromagnetic simulations were used to optimize MBalun parameters. Following optimization, two different MBalun designs were applied to MR-actively-tracked metallic guidewires and metallic-braided electrophysiology ablation catheters. Control-devices were constructed without MBaluns. MBalun performance was validated using network-analyzer quantification of current attenuation, electromagnetic Specific-Absorption-Rate (SAR) analysis, thermal tests during high SAR pulse sequences, and MRI-guided cardiovascular navigation in swine. RESULTS Electromagnetic SAR simulations resulted in ≈20 dB attenuation at the tip of the wire using six successive MBaluns. Network-analyzer tests confirmed ∼17 dB/MBalun surface-current attenuation. Thermal tests indicated temperature decreases of 5.9 °C in the MBalun-equipped guidewire tip. Both devices allowed rapid vascular navigation resulting from good torquability and MR-Tracking visibility. CONCLUSION MBaluns increased device diameter by 20%, relative to conventional devices, providing a spatially-efficient means to prevent heating during MRI. SIGNIFICANCE MBaluns allow use of long metallic components, which improves mechanical performance in active MR-guided interventional devices.
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Campbell-Washburn AE, Tavallaei MA, Pop M, Grant EK, Chubb H, Rhode K, Wright GA. Real-time MRI guidance of cardiac interventions. J Magn Reson Imaging 2017; 46:935-950. [PMID: 28493526 PMCID: PMC5675556 DOI: 10.1002/jmri.25749] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 03/29/2017] [Indexed: 11/09/2022] Open
Abstract
Cardiac magnetic resonance imaging (MRI) is appealing to guide complex cardiac procedures because it is ionizing radiation-free and offers flexible soft-tissue contrast. Interventional cardiac MR promises to improve existing procedures and enable new ones for complex arrhythmias, as well as congenital and structural heart disease. Guiding invasive procedures demands faster image acquisition, reconstruction and analysis, as well as intuitive intraprocedural display of imaging data. Standard cardiac MR techniques such as 3D anatomical imaging, cardiac function and flow, parameter mapping, and late-gadolinium enhancement can be used to gather valuable clinical data at various procedural stages. Rapid intraprocedural image analysis can extract and highlight critical information about interventional targets and outcomes. In some cases, real-time interactive imaging is used to provide a continuous stream of images displayed to interventionalists for dynamic device navigation. Alternatively, devices are navigated relative to a roadmap of major cardiac structures generated through fast segmentation and registration. Interventional devices can be visualized and tracked throughout a procedure with specialized imaging methods. In a clinical setting, advanced imaging must be integrated with other clinical tools and patient data. In order to perform these complex procedures, interventional cardiac MR relies on customized equipment, such as interactive imaging environments, in-room image display, audio communication, hemodynamic monitoring and recording systems, and electroanatomical mapping and ablation systems. Operating in this sophisticated environment requires coordination and planning. This review provides an overview of the imaging technology used in MRI-guided cardiac interventions. Specifically, this review outlines clinical targets, standard image acquisition and analysis tools, and the integration of these tools into clinical workflow. LEVEL OF EVIDENCE 1 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2017;46:935-950.
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Affiliation(s)
- Adrienne E Campbell-Washburn
- Laboratory of Imaging Technology, Biochemistry and Biophysics Center, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Mohammad A Tavallaei
- Physical Sciences Platform and Schulich Heart Program, Sunnybrook Research Institute, Toronto, Ontario, Canada
- Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
| | - Mihaela Pop
- Physical Sciences Platform and Schulich Heart Program, Sunnybrook Research Institute, Toronto, Ontario, Canada
- Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
| | - Elena K Grant
- Laboratory of Imaging Technology, Biochemistry and Biophysics Center, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
- Department of Cardiology, Children's National Medical Center, Washington, DC, USA
| | - Henry Chubb
- Division of Imaging Sciences and Biomedical Engineering, King's College London, UK
| | - Kawal Rhode
- Division of Imaging Sciences and Biomedical Engineering, King's College London, UK
| | - Graham A Wright
- Physical Sciences Platform and Schulich Heart Program, Sunnybrook Research Institute, Toronto, Ontario, Canada
- Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
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