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Lakshmanan K, Wang B, Walczyk J, Collins CM, Brown R. Three-row MRI receive array with remote circuitry to preserve radiation transparency. Phys Med Biol 2024; 69:09NT02. [PMID: 38537307 DOI: 10.1088/1361-6560/ad388c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Accepted: 03/27/2024] [Indexed: 04/18/2024]
Abstract
Objective.Up to this point, 1.5 T linac-compatible coil array layouts have been restricted to one or two rows of coils because of the desire to place radiation-opaque circuitry adjacent to the coils and outside the window through which the linac beam travels. Such layouts can limit parallel imaging performance. The purpose of this work was to design and build a three-row array in which remotely located circuits permitted a central row of coils while preserving the radiolucent window.Approach.The remote circuits consisted of a phase shifter to cancel the phase introduced by the coaxial link between the circuit and coil, followed by standard components for tuning, matching, detuning, and preamplifier decoupling. Tests were performed to compare prototype single-channel coils with remote or local circuits, which were followed by tests comparing two and three-row arrays .Main results.The single-channel coil with the remote circuit maintained 85% SNR at depths of 30 mm or more as compared to a coil with local circuit. The three-row array provided similar SNR as the two-row array, along with geometry factor advantages for parallel imaging acceleration in the head-foot direction.Significance.The remote circuit strategy could potentially support future MR-linac arrays by allowing greater flexibility in array layout compared to those confined by local circuits, which can be leveraged for parallel imaging acceleration.
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Affiliation(s)
- Karthik Lakshmanan
- Center for Advanced Imaging Innovation and Research, Department of Radiology, New York University Grossman School of Medicine, NY, United States of America
- Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine, NY, United States of America
| | - Bili Wang
- Center for Advanced Imaging Innovation and Research, Department of Radiology, New York University Grossman School of Medicine, NY, United States of America
- Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine, NY, United States of America
| | - Jerzy Walczyk
- Center for Advanced Imaging Innovation and Research, Department of Radiology, New York University Grossman School of Medicine, NY, United States of America
- Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine, NY, United States of America
| | - Christopher M Collins
- Center for Advanced Imaging Innovation and Research, Department of Radiology, New York University Grossman School of Medicine, NY, United States of America
- Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine, NY, United States of America
| | - Ryan Brown
- Center for Advanced Imaging Innovation and Research, Department of Radiology, New York University Grossman School of Medicine, NY, United States of America
- Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine, NY, United States of America
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Dubovan PI, Gilbert KM, Baron CA. A correction algorithm for improved magnetic field monitoring with distal field probes. Magn Reson Med 2023; 90:2242-2260. [PMID: 37598420 DOI: 10.1002/mrm.29781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 05/15/2023] [Accepted: 06/12/2023] [Indexed: 08/22/2023]
Abstract
PURPOSE A significant source of artifacts in MRI are field fluctuations. Field monitoring is a new technology that allows measurement of field dynamics during a scan via "field probes," which can be used to improve image reconstruction. Ideally, probes are located within the volume where gradients produce nominally linear field patterns. However, in some situations probes must be located far from isocenter where rapid field variation can arise, leading to erroneous field-monitoring characterizations and images. This work aimed to develop an algorithm that improves the robustness of field dynamics in these situations. METHODS The algorithm is split into three components. Component 1 calculates field dynamics one spatial order at a time, whereas the second implements a weighted least squares solution based on probe distance. Component 3 then calculates phase residuals and removes the residual phase for distant probes before recalculation. Two volunteers and a phantom were scanned on a 7T MRI using diffusion-weighted sequences, and field monitoring was performed. Image reconstructions were informed with field dynamics calculated conventionally, and with the correction algorithm, after which in vivo images were compared qualitatively and phantom image error was quantitatively assessed. RESULTS The algorithm was able to correct corrupted field dynamics, resulting in image-quality improvements. Significant artifact reduction was observed when correcting higher-order fits. Stepwise fitting provided the most correction benefit, which was marginally improved when adding the other correction strategies. CONCLUSION The proposed algorithm can mitigate effects of phase errors in field monitoring, providing improved characterization of field dynamics.
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Affiliation(s)
- Paul I Dubovan
- Department of Medical Biophysics, Western University, London, Ontario, Canada
- Center for Functional and Metabolic Mapping, Western University, London, Ontario, Canada
| | - Kyle M Gilbert
- Department of Medical Biophysics, Western University, London, Ontario, Canada
- Center for Functional and Metabolic Mapping, Western University, London, Ontario, Canada
| | - Corey A Baron
- Department of Medical Biophysics, Western University, London, Ontario, Canada
- Center for Functional and Metabolic Mapping, Western University, London, Ontario, Canada
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Liu S, Patel KS, Peeters S, Lin J, DiRisio AC, Vinters HV, Candler RN, Sung K, Bergsneider M. Flexible in-cavity MRI receiving coil for ultra-high-resolution imaging of the pituitary gland. J Neurosurg 2023:1-8. [PMID: 37922548 DOI: 10.3171/2023.7.jns231096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Accepted: 07/27/2023] [Indexed: 11/07/2023]
Abstract
OBJECTIVE The objective of this study was the preclinical design and construction of a flexible intrasphenoid coil aiming for submillimeter resolution of the human pituitary gland. METHODS Sphenoid sinus measurements determined coil design constraints for use in > 95% of adult patients. Temperature safety parameters were tested. The 2-cm-diameter coil prototype was positioned in the sphenoid sinus of cadaveric human heads utilizing the transnasal endoscopic approach that is used clinically. Signal-to-noise ratio (SNR) was estimated for the transnasal coil prototype compared with a standard clinical head coil. One cadaveric pituitary gland was explanted and histologically examined for correlation to the imaging findings. RESULTS With the coil positioned directly atop the sella turcica at a 0° angle of the B0 static field, the craniocaudal distance (21.2 ± 0.8 mm) was the limiting constraint. Phantom experiments showed no detectable change in temperature at two sites over 15 minutes. The flexible coil was placed transnasally in cadaveric specimens using an endoscopic approach. The image quality was subjectively superior at higher spatial resolutions relative to that with the commercial 20-channel head coil. An average 17-fold increase in the SNR was achieved within the pituitary gland. Subtle findings visualized only with the transnasal coil had potential pathological correlation with immunohistochemical findings. CONCLUSIONS A transnasal radiofrequency coil feasibly provides a 17-fold boost in the SNR at 3 T. The ability to safely improve the quality of pituitary imaging may be helpful in the identification and subsequent resection of small functional pituitary lesions.
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Affiliation(s)
- Siyuan Liu
- 1Department of Electrical and Computer Engineering, Samueli School of Electrical and Computer Engineering, University of California, Los Angeles
| | - Kunal S Patel
- 2Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles
- 3Department of Radiological Sciences, Brain Tumor Imaging Laboratory, University of California, Los Angeles
| | - Sophie Peeters
- 2Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles
| | - Jiahao Lin
- 1Department of Electrical and Computer Engineering, Samueli School of Electrical and Computer Engineering, University of California, Los Angeles
- Departments of4Radiological Sciences and
| | - Aislyn C DiRisio
- 2Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles
| | | | - Rob N Candler
- 1Department of Electrical and Computer Engineering, Samueli School of Electrical and Computer Engineering, University of California, Los Angeles
- 6California NanoSystems Institute, Los Angeles, California
| | | | - Marvin Bergsneider
- 2Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles
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Rios NL, Gilbert KM, Papp D, Cereza G, Foias A, Rangaprakash D, May MW, Guerin B, Wald LL, Keil B, Stockmann JP, Barry RL, Cohen-Adad J. An 8-channel Tx dipole and 20-channel Rx loop coil array for MRI of the cervical spinal cord at 7 Tesla. NMR Biomed 2023; 36:e5002. [PMID: 37439129 PMCID: PMC10733907 DOI: 10.1002/nbm.5002] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 05/10/2023] [Accepted: 06/15/2023] [Indexed: 07/14/2023]
Abstract
The quality of cervical spinal cord images can be improved by the use of tailored radiofrequency (RF) coil solutions for ultrahigh field imaging; however, very few commercial and research 7-T RF coils currently exist for the spinal cord, and in particular, those with parallel transmission (pTx) capabilities. This work presents the design, testing, and validation of a pTx/Rx coil for the human neck and cervical/upper thoracic spinal cord. The pTx portion is composed of eight dipoles to ensure high homogeneity over this large region of the spinal cord. The Rx portion is made up of twenty semiadaptable overlapping loops to produce high signal-to-noise ratio (SNR) across the patient population. The coil housing is designed to facilitate patient positioning and comfort, while also being tight fitting to ensure high sensitivity. We demonstrate RF shimming capabilities to optimize B1 + uniformity, power efficiency, and/or specific absorption rate efficiency. B1 + homogeneity, SNR, and g-factor were evaluated in adult volunteers and demonstrated excellent performance from the occipital lobe down to the T4-T5 level. We compared the proposed coil with two state-of-the-art head and head/neck coils, confirming its superiority in the cervical and upper thoracic regions of the spinal cord. This coil solution therefore provides a convincing platform for producing the high image quality necessary for clinical and research scanning of the upper spinal cord.
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Affiliation(s)
- Nibardo Lopez Rios
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montréal, Montréal, QC, Canada
| | - Kyle M. Gilbert
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, ON, Canada
| | - Daniel Papp
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montréal, Montréal, QC, Canada
| | - Gaspard Cereza
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montréal, Montréal, QC, Canada
| | - Alexandru Foias
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montréal, Montréal, QC, Canada
| | - D. Rangaprakash
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA
- Harvard Medical School, Boston, MA, USA
| | - Markus W. May
- Erwin L. Hahn Institute for Magnetic Resonance Imaging, University of Duisburg-Essen, Essen, Germany
- High Field and Hybrid MR Imaging, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Bastien Guerin
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA
- Harvard Medical School, Boston, MA, USA
| | - Lawrence L. Wald
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA
- Harvard Medical School, Boston, MA, USA
- Harvard-Massachusetts Institute of Technology Health Sciences & Technology, Cambridge, MA, USA
| | - Boris Keil
- Institute of Medical Physics and Radiation Protection, University of Applied Sciences Mittelhessen, Giessen, Germany
- Department of Diagnostic and Interventional Radiology, University Hospital Marburg, Philipps University of Marburg, Marburg, Germany
| | - Jason P. Stockmann
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA
- Harvard Medical School, Boston, MA, USA
| | - Robert L. Barry
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA
- Harvard Medical School, Boston, MA, USA
- Harvard-Massachusetts Institute of Technology Health Sciences & Technology, Cambridge, MA, USA
| | - Julien Cohen-Adad
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montréal, Montréal, QC, Canada
- Functional Neuroimaging Unit, CRIUGM, Université de Montréal, Montreal, QC, Canada
- Mila – Quebec AI Institute, Montreal, QC, Canada
- Centre de recherche du CHU Sainte-Justine, Université de Montréal, Montréal, QC, Canada
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Obermann M, Nohava L, Frass-Kriegl R, Soanca O, Ginefri JC, Felblinger J, Clauser P, Baltzer PA, Laistler E. Panoramic Magnetic Resonance Imaging of the Breast With a Wearable Coil Vest. Invest Radiol 2023; 58:799-810. [PMID: 37227137 PMCID: PMC10581436 DOI: 10.1097/rli.0000000000000991] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 04/21/2023] [Indexed: 05/26/2023]
Abstract
BACKGROUND Breast cancer, the most common malignant cancer in women worldwide, is typically diagnosed by x-ray mammography, which is an unpleasant procedure, has low sensitivity in women with dense breasts, and involves ionizing radiation. Breast magnetic resonance imaging (MRI) is the most sensitive imaging modality and works without ionizing radiation, but is currently constrained to the prone imaging position due to suboptimal hardware, therefore hampering the clinical workflow. OBJECTIVES The aim of this work is to improve image quality in breast MRI, to simplify the clinical workflow, shorten measurement time, and achieve consistency in breast shape with other procedures such as ultrasound, surgery, and radiation therapy. MATERIALS AND METHODS To this end, we propose "panoramic breast MRI"-an approach combining a wearable radiofrequency coil for 3 T breast MRI (the "BraCoil"), acquisition in the supine position, and a panoramic visualization of the images. We demonstrate the potential of panoramic breast MRI in a pilot study on 12 healthy volunteers and 1 patient, and compare it to the state of the art. RESULTS With the BraCoil, we demonstrate up to 3-fold signal-to-noise ratio compared with clinical standard coils and acceleration factors up to 6 × 4. Panoramic visualization of supine breast images reduces the number of slices to be viewed by a factor of 2-4. CONCLUSIONS Panoramic breast MRI allows for high-quality diagnostic imaging and facilitated correlation to other diagnostic and interventional procedures. The developed wearable radiofrequency coil in combination with dedicated image processing has the potential to improve patient comfort while enabling more time-efficient breast MRI compared with clinical coils.
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Abel F, Tan ET, Lunenburg M, van Leeuwen C, van Hooren T, van Uden M, Arteaga C, Vincent J, Robb F, Sneag DB. Flexible array coil for cervical and extraspinal (FACE) MRI at 3.0 Tesla. Phys Med Biol 2023; 68:215011. [PMID: 37816375 DOI: 10.1088/1361-6560/ad0217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2023] [Accepted: 10/10/2023] [Indexed: 10/12/2023]
Abstract
Objective.High-resolution MRI of the cervical spine (c-spine) and extraspinal neck region requires close-fitting receiver coils to maximize the signal-to-noise ratio (SNR). Conventional, rigid C-spine receiver coils do not adequately contour to the neck to accommodate varying body shapes, resulting in suboptimal SNR. Recent innovations in flexible surface coil array designs may provide three-dimensional (3D) bendability and conformability to optimize SNR, while improving capabilities for higher acceleration factors.Approach.This work describes the design, implementation, and preliminaryin vivotesting of a novel, conformal 23-channel receive-only flexible array for cervical and extraspinal (FACE) MRI at 3-Tesla (T), with use of high-impedance elements to enhance the coil's flexibility. Coil performance was tested by assessing SNR and geometry factors (g-factors) in a phantom compared to a conventional 21-channel head-neck-unit (HNU).In vivoimaging was performed in healthy human volunteers and patients using high-resolution c-spine and neck MRI protocols at 3T, including MR neurography (MRN).Main results.Mean SNR with the FACE was 141%-161% higher at left, right, and posterior off-isocenter positions and 4% higher at the isocenter of the phantom compared to the HNU. Parallel imaging performance was comparable for an acceleration factor (R) = 2 × 2 between the two coils, but improved forR= 3 × 3 with meang-factors ranging from 1.46-2.15 with the FACE compared to 2.36-3.62 obtained with the HNU. Preliminary human volunteer and patient testing confirmed that equivalent or superior image quality could be obtained for evaluation of osseous and soft tissue structures of the cervical region with the FACE.Significance.A conformal and highly flexible cervical array with high-impedance coil elements can potentially enable higher-resolution imaging for cervical imaging.
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Affiliation(s)
- Frederik Abel
- Hospital for Special Surgery, 535 East 70th Street, NY 10021, United States of America
| | - Ek T Tan
- Hospital for Special Surgery, 535 East 70th Street, NY 10021, United States of America
| | - Martijn Lunenburg
- Tesla Dynamic Coils, Schimminck 12, 5301 Zaltbommel, The Netherlands
| | - Carel van Leeuwen
- Tesla Dynamic Coils, Schimminck 12, 5301 Zaltbommel, The Netherlands
| | - Thijs van Hooren
- Tesla Dynamic Coils, Schimminck 12, 5301 Zaltbommel, The Netherlands
| | - Mark van Uden
- Tesla Dynamic Coils, Schimminck 12, 5301 Zaltbommel, The Netherlands
| | - Catalina Arteaga
- Tesla Dynamic Coils, Schimminck 12, 5301 Zaltbommel, The Netherlands
| | - Jana Vincent
- GE HealthCare, 1515 Danner Dr, 44202 Aurora, OH, United States of America
| | - Fraser Robb
- GE HealthCare, 1515 Danner Dr, 44202 Aurora, OH, United States of America
| | - Darryl B Sneag
- Hospital for Special Surgery, 535 East 70th Street, NY 10021, United States of America
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Motovilova E, Ching T, Vincent J, Shin J, Tan ET, Taracila V, Robb F, Hashimoto M, Sneag DB, Winkler SA. Dual-Channel Stretchable, Self-Tuning, Liquid Metal Coils and Their Fabrication Techniques. Sensors (Basel) 2023; 23:7588. [PMID: 37688046 PMCID: PMC10490642 DOI: 10.3390/s23177588] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Revised: 08/28/2023] [Accepted: 08/29/2023] [Indexed: 09/10/2023]
Abstract
Flexible and stretchable radiofrequency coils for magnetic resonance imaging represent an emerging and rapidly growing field. The main advantage of such coil designs is their conformal nature, enabling a closer anatomical fit, patient comfort, and freedom of movement. Previously, we demonstrated a proof-of-concept single element stretchable coil design with a self-tuning smart geometry. In this work, we evaluate the feasibility of scaling this coil concept to a multi-element coil array and the associated engineering and manufacturing challenges. To this goal, we study a dual-channel coil array using full-wave simulations, bench testing, in vitro, and in vivo imaging in a 3 T scanner. We use three fabrication techniques to manufacture dual-channel receive coil arrays: (1) single-layer casting, (2) double-layer casting, and (3) direct-ink-writing. All fabricated arrays perform equally well on the bench and produce similar sensitivity maps. The direct-ink-writing method is found to be the most advantageous fabrication technique for fabrication speed, accuracy, repeatability, and total coil array thickness (0.6 mm). Bench tests show excellent frequency stability of 128 ± 0.6 MHz (0% to 30% stretch). Compared to a commercial knee coil array, the stretchable coil array is more conformal to anatomy and provides 50% improved signal-to-noise ratio in the region of interest.
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Affiliation(s)
- Elizaveta Motovilova
- Department of Radiology, Weill Cornell Medicine, New York, NY 10065, USA
- Department of Radiology and Imaging, Hospital for Special Surgery, New York, NY 10021, USA
| | - Terry Ching
- Pillar of Engineering Product Development, Singapore University of Technology and Design, Singapore 487372, Singapore
- Digital Manufacturing and Design (DManD) Centre, Singapore University of Technology and Design, Singapore 487372, Singapore
- Department of Biomedical Engineering, National University of Singapore, Singapore 117583, Singapore
| | | | - James Shin
- Department of Radiology, Weill Cornell Medicine, New York, NY 10065, USA
| | - Ek Tsoon Tan
- Department of Radiology and Imaging, Hospital for Special Surgery, New York, NY 10021, USA
| | | | | | - Michinao Hashimoto
- Pillar of Engineering Product Development, Singapore University of Technology and Design, Singapore 487372, Singapore
- Digital Manufacturing and Design (DManD) Centre, Singapore University of Technology and Design, Singapore 487372, Singapore
| | - Darryl B. Sneag
- Department of Radiology and Imaging, Hospital for Special Surgery, New York, NY 10021, USA
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8
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Gilbert KM, Nichols ES, Gati JS, Duerden EG. A radiofrequency coil for infants and toddlers. NMR Biomed 2023:e4928. [PMID: 36939270 DOI: 10.1002/nbm.4928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 03/06/2023] [Accepted: 03/07/2023] [Indexed: 06/18/2023]
Abstract
Infants and toddlers are a challenging population upon which to perform magnetic resonance imaging (MRI) of the brain, both in research and clinical settings. Because of the large range in head size during the early years of development, paediatric neuro-MRI requires a radiofrequency (RF) coil, or set of coils, that is tailored to head size to provide the highest image quality. Mitigating techniques must also be employed to reduce and correct for subject motion. This manuscript describes an RF coil with a tailored mechanical-electrical design that can adapt to the head size of 3-month-old infants to 3-year-old toddlers. The RF coil was designed with tight-fitting coil elements to improve the signal-to-noise ratio (SNR) in comparison with commercially available adult head coils, while simultaneously aiding in immobilization. The coil was designed without visual obstruction to facilitate an unimpeded view of the child's face and the potential application of camera or motion-tracking systems. Despite the lack of elements over the face, the paediatric coil produced higher SNR over most of the brain compared with adult coils, including more than twofold in the periphery. Acceleration rates of fourfold in each Cartesian direction could be achieved. High SNR allowed for short acquisition times through accelerated imaging protocols and reduced the probability of motion during a scan. Modification of the acquisition protocol, with immobilization of the head through the adjustable coil geometry, and subsequently being combined with a motion-tracking system, provides a compelling platform for scanning paediatric populations without sedation and with improved image quality.
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Affiliation(s)
- Kyle M Gilbert
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, Ontario, Canada
- Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
| | - Emily S Nichols
- Applied Psychology, Faculty of Education, The University of Western Ontario, London, Ontario, Canada
- Western Institute for Neuroscience, The University of Western Ontario, London, Ontario, Canada
| | - Joseph S Gati
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, Ontario, Canada
- Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
| | - Emma G Duerden
- Applied Psychology, Faculty of Education, The University of Western Ontario, London, Ontario, Canada
- Western Institute for Neuroscience, The University of Western Ontario, London, Ontario, Canada
- Department of Pediatrics, Schulich School of Medicine and Dentistry, London, Ontario, Canada
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9
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Rios NL, Gilbert KM, Papp D, Cereza G, Foias A, Rangaprakash D, May MW, Guerin B, Wald LL, Keil B, Stockmann JP, Barry RL, Cohen-Adad J. 8-channel Tx dipole and 20-channel Rx loop coil array for MRI of the cervical spinal cord at 7 Tesla. bioRxiv 2023:2023.02.08.527664. [PMID: 36798276 PMCID: PMC9934596 DOI: 10.1101/2023.02.08.527664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
The quality of cervical spinal cord images can be improved by the use of tailored radiofrequency coil solutions for ultra-high field imaging; however, very few commercial and research 7 Tesla radiofrequency coils currently exist for the spinal cord, and in particular those with parallel transmit capabilities. This work presents the design, testing and validation of a pTx/Rx coil for the human neck and cervical/upper-thoracic spinal cord. The pTx portion is composed of 8 dipoles to ensure high homogeneity over this large region of the spinal cord. The Rx portion is made of 20 semi-adaptable overlapping loops to produce high Signal-to-noise ratio (SNR) across the patient population. The coil housing is designed to facilitate patient positioning and comfort, while being tight fitting to ensure high sensitivity. We demonstrate RF shimming capabilities to optimize B 1 + uniformity, power efficiency and/or specific absorption rate (SAR) efficiency. B 1 + homogeneity, SNR and g-factor was evaluated in adult volunteers and demonstrated excellent performance from the occipital lobe down to the T4-T5 level. We compared the proposed coil with two state-of-the-art head and head/neck coils, confirming its superiority in the cervical and upper-thoracic regions of the spinal cord. This coil solution therefore provides a convincing platform for producing the high image quality necessary for clinical and research scanning of the upper spinal cord.
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Affiliation(s)
- Nibardo Lopez Rios
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montréal, Montreal, QC, Canada
| | - Kyle M. Gilbert
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, ON, Canada
| | - Daniel Papp
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montréal, Montreal, QC, Canada
| | - Gaspard Cereza
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montréal, Montreal, QC, Canada
| | - Alexandru Foias
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montréal, Montreal, QC, Canada
| | - D. Rangaprakash
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA
- Harvard Medical School, Boston, MA, USA
| | - Markus W. May
- Erwin L. Hahn Institute for Magnetic Resonance Imaging, University of Duisburg-Essen, Essen, Germany
- High Field and Hybrid MR Imaging, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Bastien Guerin
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA
- Harvard Medical School, Boston, MA, USA
| | - Lawrence L. Wald
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA
- Harvard Medical School, Boston, MA, USA
- Harvard-Massachusetts Institute of Technology Health Sciences & Technology, Cambridge, MA, USA
| | - Boris Keil
- Institute of Medical Physics and Radiation Protection, University of Applied Sciences Mittelhessen, Giessen, Germany
- Department of Diagnostic and Interventional Radiology, University Hospital Marburg, Philipps University of Marburg, Marburg, Germany
| | - Jason P. Stockmann
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA
- Harvard Medical School, Boston, MA, USA
| | - Robert L. Barry
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA
- Harvard Medical School, Boston, MA, USA
- Harvard-Massachusetts Institute of Technology Health Sciences & Technology, Cambridge, MA, USA
| | - Julien Cohen-Adad
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montréal, Montreal, QC, Canada
- Functional Neuroimaging Unit, CRIUGM, Université de Montréal, Montreal, QC, Canada
- Mila – Quebec AI Institute, Montreal, QC, Canada
- Centre de recherche du CHU Sainte-Justine, Université de Montréal, Montréal, QC, Canada
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Giannakopoulos II, Guryev GD, Serralles JEC, Paska J, Zhang B, Daniel L, White JK, Collins CM, Lattanzi R. A Hybrid Volume-Surface Integral Equation Method for Rapid Electromagnetic Simulations in MRI. IEEE Trans Biomed Eng 2023; 70:105-114. [PMID: 35759593 PMCID: PMC9875343 DOI: 10.1109/tbme.2022.3186235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
OBJECTIVE We developed a hybrid volume surface integral equation (VSIE) method based on domain decomposition to perform fast and accurate magnetic resonance imaging (MRI) simulations that include both remote and local conductive elements. METHODS We separated the conductive surfaces present in MRI setups into two domains and optimized electromagnetic (EM) modeling for each case. Specifically, interactions between the body and EM waves originating from local radiofrequency (RF) coils were modeled with the precorrected fast Fourier transform, whereas the interactions with remote conductive surfaces (RF shield, scanner bore) were modeled with a novel cross tensor train-based algorithm. We compared the hybrid-VSIE with other VSIE methods for realistic MRI simulation setups. RESULTS The hybrid-VSIE was the only practical method for simulation using 1 mm voxel isotropic resolution (VIR). For 2 mm VIR, our method could be solved at least 23 times faster and required 760 times lower memory than traditional VSIE methods. CONCLUSION The hybrid-VSIE demonstrated a marked improvement in terms of convergence times of the numerical EM simulation compared to traditional approaches in multiple realistic MRI scenarios. SIGNIFICANCE The efficiency of the novel hybrid-VSIE method could enable rapid simulations of complex and comprehensive MRI setups.
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11
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Lee YH, Song K, Yang J, Kang WJ, Lee KS, Kim MJ, Kim E, Heo D, Choe B, Suh J. Fabrication and evaluation of bilateral Helmholtz radiofrequency coil for thermo-stable breast image with reduced artifacts. J Appl Clin Med Phys 2022; 23:e13483. [PMID: 34854217 PMCID: PMC8803304 DOI: 10.1002/acm2.13483] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 09/26/2021] [Accepted: 11/10/2021] [Indexed: 11/17/2022] Open
Abstract
PURPOSE The positron emission tomography (PET)-magnetic resonance (MR) system is a newly emerging technique that yields hybrid images with high-resolution anatomical and metabolic information. With PET-MR imaging, a definitive diagnosis of breast abnormalities will be possible with high spatial accuracy and images will be acquired for the optimal fusion of anatomic locations. Therefore, we propose a PET-compatible two-channel breast MR coil with minimal disturbance to image acquisition which can be used for simultaneous PET-MR imaging in patients with breast cancer. MATERIALS AND METHODS For coil design and construction, the conductor loops of the Helmholtz coil were tuned, matched, and subdivided with nonmagnetic components. Element values were optimized with an electromagnetic field simulation. Images were acquired on a GE 600 PET-computed tomography (CT) and GE 3.0 T MR system. For this study, we used the T1-weighted image (volunteer; repetition time (TR), 694 ms; echo time (TE), 9.6 ms) and T2-weighted image (phantom; TR, 8742 ms; TE, 104 ms) with the fast spin-echo sequence. RESULTS The results of measuring image factors with the proposed radiofrequency (RF) coil and standard conventional RF coil were as follows: signal-to-noise ratio (breast; 207.7 vs. 175.2), percent image uniformity (phantom; 89.22%-91.27% vs. 94.63%-94.77%), and Hounsfield units (phantom; -4.51 vs. 2.38). CONCLUSIONS Our study focused on the feasibility of proposed two-channel Helmholtz loops (by minimizing metallic components and soldering) for PET-MR imaging and found the comparable image quality to the standard conventional coil. We believe our work will help significantly to improve image quality with the development of a less metallic breast MR coil.
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Affiliation(s)
- Young Han Lee
- Department of RadiologySeverance HospitalResearch Institute of Radiological ScienceYonsei University College of MedicineSeoulRepublic of Korea
| | - Kyu‐Ho Song
- Department of RadiologyWashington University School of MedicineSt. LouisMissouriUSA
| | - Jaemoon Yang
- Department of RadiologySeverance HospitalResearch Institute of Radiological ScienceYonsei University College of MedicineSeoulRepublic of Korea
| | - Won Jun Kang
- Department of Nuclear MedicineSeverance HospitalYonsei University College of MedicineSeoulRepublic of Korea
| | - Keum Sil Lee
- Department of RadiologyStanford University School of MedicineStanfordCaliforniaUSA
| | - Min Jung Kim
- Department of Nuclear MedicineSeverance HospitalYonsei University College of MedicineSeoulRepublic of Korea
| | - Eun‐Kyung Kim
- Department of RadiologySeverance HospitalResearch Institute of Radiological ScienceYonsei University College of MedicineSeoulRepublic of Korea
| | - Dan Heo
- Department of RadiologySeverance HospitalResearch Institute of Radiological ScienceYonsei University College of MedicineSeoulRepublic of Korea
| | - Bo‐Young Choe
- Department of Biomedical EngineeringCollege of Medicineand Research Institute of Biomedical EngineeringThe Catholic University of KoreaSeoulRepublic of Korea
| | - Jin‐Suck Suh
- Department of RadiologySeverance HospitalResearch Institute of Radiological ScienceYonsei University College of MedicineSeoulRepublic of Korea
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12
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Gilbert KM, Dubovan PI, Gati JS, Menon RS, Baron CA. Integration of an RF coil and commercial field camera for ultrahigh-field MRI. Magn Reson Med 2021; 87:2551-2565. [PMID: 34932225 DOI: 10.1002/mrm.29130] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 11/16/2021] [Accepted: 12/03/2021] [Indexed: 11/08/2022]
Abstract
PURPOSE To develop an RF coil with an integrated commercial field camera for ultrahigh field (7T) neuroimaging. The RF coil would operate within a head-only gradient coil and be subject to the corresponding design constraints. The RF coil can thereafter be used for subject-specific correction of k-space trajectories-notably in gradient-sensitive sequences such as single-shot spiral imaging. METHODS The transmit and receive performance was evaluated before and after the integration of field probes, whereas field probes were evaluated when in an optimal configuration external to the coil and after their integration. Diffusion-weighted EPI and single-shot spiral acquisitions were employed to evaluate the efficacy of correcting higher order field perturbations and the consequent effect on image quality. RESULTS Field probes had a negligible effect on RF-coil performance, including the transmit efficiency, transmit uniformity, and mean SNR over the brain. Modest reductions in field-probe signal lifetimes were observed, caused primarily by nonidealities in the gradient and shim fields of the head-only gradient coil at the probe positions. The field-monitoring system could correct up to second-order field perturbations in single-shot spiral imaging. CONCLUSION The integrated RF coil and field camera was capable of concurrent-field monitoring within a 7T head-only scanner and facilitated the subsequent correction of k-space trajectories during spiral imaging.
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Affiliation(s)
- Kyle M Gilbert
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, Ontario, Canada.,Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
| | - Paul I Dubovan
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, Ontario, Canada.,Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
| | - Joseph S Gati
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, Ontario, Canada.,Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
| | - Ravi S Menon
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, Ontario, Canada.,Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
| | - Corey A Baron
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, Ontario, Canada.,Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
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13
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Gilbert KM, Klassen LM, Mashkovtsev A, Zeman P, Menon RS, Gati JS. Radiofrequency coil for routine ultra-high-field imaging with an unobstructed visual field. NMR Biomed 2021; 34:e4457. [PMID: 33305466 DOI: 10.1002/nbm.4457] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 11/17/2020] [Indexed: 06/12/2023]
Abstract
Many neuroscience applications have adopted functional MRI as a tool to investigate the healthy and diseased brain during the completion of a task. While ultra-high-field MRI has allowed for improved contrast and signal-to-noise ratios during functional MRI studies, it remains a challenge to create local radiofrequency coils that can accommodate an unobstructed visual field and be suitable for routine use, while at the same time not compromise performance. Performance (both during transmission and reception) can be improved by using close-fitting coils; however, maintaining sensitivity over the whole brain often requires the introduction of coil elements proximal to the eyes, thereby partially occluding the subject's visual field. This study presents a 7 T head coil, with eight transmit dipoles and 32 receive loops, that is designed to remove visual obstructions from the subject's line of sight, allowing for an unencumbered view of visual stimuli, the reduction of anxiety induced from small enclosures, and the potential for eye-tracking measurements. The coil provides a practical solution for routine imaging, including a split design (anterior and posterior halves) that facilitates subject positioning, including those with impaired mobility, and the placement of devices required for patient comfort and motion reduction. The transmit and receive coils displayed no degradation of performance due to adaptions to the design topology (both mechanical and electrical) required to create an unobstructed visual field. All computer-aided design files, electromagnetic simulation models, transmit field maps and local specific absorption rate matrices are provided to promote reproduction.
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Affiliation(s)
- Kyle M Gilbert
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, Ontario, Canada
- Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
| | - L Martyn Klassen
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, Ontario, Canada
| | - Alexander Mashkovtsev
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, Ontario, Canada
| | - Peter Zeman
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, Ontario, Canada
| | - Ravi S Menon
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, Ontario, Canada
- Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
| | - Joseph S Gati
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, Ontario, Canada
- Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
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14
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Li X, Gong H, Pan JW, Hetherington HP, Rispoli JV. Modelling and B1 Shim Analysis of 16-Element Transceiver Array at 7 T. Int Conf Electromagn Adv Appl 2019; 2019:1291-1295. [PMID: 32181448 PMCID: PMC7075652 DOI: 10.1109/iceaa.2019.8879006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The work examines the workflow of using commercially available software for electromagnetic modelling and validation of a transceiver array coil operating at 298 MHz for magnetic resonance imaging and spectroscopy at 7 T. The coneshaped, tight-fit parallel transmit head array consists of two rows with eight loop coils per row and transmits two distinct spatial distributions by means of B 1 shimming. Considerations for finite-difference time-domain simulation setup and post-processing with circuit-domain co-simulation are examined, as is the generation of virtual observation points suitable for online safety monitoring.
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Affiliation(s)
- Xin Li
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
| | - Haoda Gong
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, USA
| | - Jullie W Pan
- Department of Neurology, University of Pittsburgh, Pittsburgh, PA, USA
| | | | - Joseph V Rispoli
- Weldon School of Biomedical Engineering, School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, USA
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15
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Navarro de Lara LI, Frass-Kriegl R, Renner A, Sieg J, Pichler M, Bogner T, Moser E, Beyer T, Birkfellner W, Figl M, Laistler E. Design, Implementation, and Evaluation of a Head and Neck MRI RF Array Integrated with a 511 keV Transmission Source for Attenuation Correction in PET/MR. Sensors (Basel) 2019; 19:s19153297. [PMID: 31357545 PMCID: PMC6696210 DOI: 10.3390/s19153297] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 07/23/2019] [Accepted: 07/25/2019] [Indexed: 01/13/2023]
Abstract
The goal of this work is to further improve positron emission tomography (PET) attenuation correction and magnetic resonance (MR) sensitivity for head and neck applications of PET/MR. A dedicated 24-channel receive-only array, fully-integrated with a hydraulic system to move a transmission source helically around the patient and radiofrequency (RF) coil array, is designed, implemented, and evaluated. The device enables the calculation of attenuation coefficients from PET measurements at 511 keV including the RF coil and the particular patient. The RF coil design is PET-optimized by minimizing photon attenuation from coil components and housing. The functionality of the presented device is successfully demonstrated by calculating the attenuation map of a water bottle based on PET transmission measurements; results are in excellent agreement with reference values. It is shown that the device itself has marginal influence on the static magnetic field B0 and the radiofrequency transmit field B1 of the 3T PET/MR system. Furthermore, the developed RF array is shown to outperform a standard commercial 16-channel head and neck coil in terms of signal-to-noise ratio (SNR) and parallel imaging performance. In conclusion, the presented hardware enables accurate calculation of attenuation maps for PET/MR systems while improving the SNR of corresponding MR images in a single device without degrading the B0 and B1 homogeneity of the scanner.
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Affiliation(s)
- Lucia Isabel Navarro de Lara
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Roberta Frass-Kriegl
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Andreas Renner
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
- Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria
| | - Jürgen Sieg
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Michael Pichler
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Thomas Bogner
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Ewald Moser
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Thomas Beyer
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Wolfgang Birkfellner
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Michael Figl
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Elmar Laistler
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria.
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16
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Abstract
PURPOSE To describe a new bench measurement based on quality (Q) factors to estimate the coil noise relative to the sample noise of dipole antennas at 7 T. METHODS Placing a dipole antenna close to a highly conductive sample surrogate (HCSS) greatly reduces radiation loss, and using QHCSS gives a more accurate estimate of coil resistance than Qunloaded . Instead of using the ratio of unloaded and sample-loaded Q factors, the ratio of HCSS-loaded and sample-loaded Q factors should be used at ultra-high fields. A series of simulations were carried out to analyze the power budget of sample-loaded or HCSS-loaded dipole antennas. Two prototype dipole antennas were also constructed for bench measurements to validate the simulations. RESULTS Simulations showed that radiation loss was suppressed when the dipole antenna was HCSS-loaded, and coil loss was largely the same as when the dipole was loaded by the sample. Bench measurements also showed good alignment with simulations. CONCLUSIONS Using the ratio QHCSS /Qloaded gives a good estimate of the coil loss for dipole antennas at 7 T, and provides a convenient bench measurement to predict the body noise dominance of dipole antenna designs. The new approach also applies to conventional surface loop coils at ultra-high fields. Magn Reson Med 79:1773-1780, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Gang Chen
- Center for Advanced Imaging Innovation and Research (CAI2R) and Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York, USA.,The Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, New York, New York, USA
| | - Christopher M Collins
- Center for Advanced Imaging Innovation and Research (CAI2R) and Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York, USA.,The Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, New York, New York, USA
| | - Daniel K Sodickson
- Center for Advanced Imaging Innovation and Research (CAI2R) and Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York, USA.,The Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, New York, New York, USA
| | - Graham C Wiggins
- Center for Advanced Imaging Innovation and Research (CAI2R) and Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York, USA
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17
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Abstract
The birdcage (BC) coil is currently being utilized for uniform radiofrequency (RF) transmit/receive (Tx/Rx) or Tx-only configuration in many magnetic resonance (MR) imaging applications, but insufficient magnetic flux (|B1|) density and their non-uniform distribution still exists in high-field (HF) environments. We demonstrate that the asymmetric birdcage (ABC) transmit/receive (Tx/Rx) volume coil, which is a modified standard birdcage (SBC) coil with the end ring split into two halves, is suitable for improving the |B1| sensitivity in 7T small-animal MR imaging. Cylindrical SBC and ABC coils with 35 mm diameter were constructed and bench tested for mouse body MR imaging at 300 MHz using a 7T scanner. To assess the ABC coil performance, computational electromagnetic (EM) simulation and 7T MR experiment were performed by using a cylindrical phantom and in vivo mouse body and quantitatively compared with the SBC coil in terms of |B1| distribution, RF transmit (|B1+|) field, and signal-to-noise ratio (SNR). The bench measurements of the two BC coils are similar, yielding a quality value (Q-value) of 74.42 for the SBC coil and 77.06 for the ABC coil. The computational calculation results clearly show that the proposed ABC coil offers superior |B1| field and |B1+| field sensitivity in the central axial slice compared with the SBC coil. There was also high SNR and uniformly distributed flip angle (FA) under the loaded condition of mouse body in the 7T experiment. Although ABC geometry allows a further increase in the |B1| field and |B1+| field sensitivity in only the central axial slice, the geometrical modification of the SBC coil can make a high performance RF coil feasible in the central axial slice and also make target imaging possible in the diagonal direction.
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Affiliation(s)
- Kyoung-Nam Kim
- Center for Molecular and Cellular Imaging, Samsung Biomedical Research Institute
| | - Sang-Doc Han
- Center for Molecular and Cellular Imaging, Samsung Biomedical Research Institute
| | - Jeung-Hoon Seo
- Center for Molecular and Cellular Imaging, Samsung Biomedical Research Institute
| | - Phil Heo
- Department of Health Sciences and Technology, Samsung Advanced Institute for Health Science and Technology, Sungkyunkwan University
| | - Dongkyeom Yoo
- Center for Molecular and Cellular Imaging, Samsung Biomedical Research Institute
| | - Geun Ho Im
- Center for Molecular and Cellular Imaging, Samsung Biomedical Research Institute
| | - Jung Hee Lee
- Department of Health Sciences and Technology, Samsung Advanced Institute for Health Science and Technology, Sungkyunkwan University.,Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine
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18
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Linz P, Santoro D, Renz W, Rieger J, Ruehle A, Ruff J, Deimling M, Rakova N, Muller DN, Luft FC, Titze J, Niendorf T. Skin sodium measured with ²³Na MRI at 7.0 T. NMR Biomed 2015; 28:54-62. [PMID: 25328128 DOI: 10.1002/nbm.3224] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Revised: 09/10/2014] [Accepted: 09/10/2014] [Indexed: 06/04/2023]
Abstract
Skin sodium (Na(+) ) storage, as a physiologically important regulatory mechanism for blood pressure, volume regulation and, indeed, survival, has recently been rediscovered. This has prompted the development of MRI methods to assess Na(+) storage in humans ((23) Na MRI) at 3.0 T. This work examines the feasibility of high in-plane spatial resolution (23) Na MRI in skin at 7.0 T. A two-channel transceiver radiofrequency (RF) coil array tailored for skin MRI at 7.0 T (f = 78.5 MHz) is proposed. Specific absorption rate (SAR) simulations and a thorough assessment of RF power deposition were performed to meet the safety requirements. Human skin was examined in an in vivo feasibility study using two-dimensional gradient echo imaging. Normal male adult volunteers (n = 17; mean ± standard deviation, 46 ± 18 years; range, 20-79 years) were investigated. Transverse slices of the calf were imaged with (23) Na MRI using a high in-plane resolution of 0.9 × 0.9 mm(2) . Skin Na(+) content was determined using external agarose standards covering a physiological range of Na(+) concentrations. To assess the intra-subject reproducibility, each volunteer was examined three to five times with each session including a 5-min walk and repositioning/preparation of the subject. The age dependence of skin Na(+) content was investigated. The (23) Na RF coil provides improved sensitivity within a range of 1 cm from its surface versus a volume RF coil which facilitates high in-plane spatial resolution imaging of human skin. Intra-subject variability of human skin Na(+) content in the volunteer population was <10.3%. An age-dependent increase in skin Na(+) content was observed (r = 0.78). The assignment of Na(+) stores with (23) Na MRI techniques could be improved at 7.0 T compared with current 3.0 T technology. The benefits of such improvements may have the potential to aid basic research and clinical applications designed to unlock questions regarding the Na(+) balance and Na(+) storage function of skin.
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Affiliation(s)
- Peter Linz
- Interdisciplinary Center for Clinical Research, Nikolaus-Fiebiger-Center for Molecular Medicine, Friedrich-Alexander-University Erlangen-Nürnberg, Germany
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19
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Abstract
Proton and heteronuclear MRI/MRS using dual-tuned (DT) coils could provide both anatomical and metabolic images without repositioning the subject. However, it is technologically challenging to attain sufficiently electromagnetic (EM) decoupling between the heteronuclear channel and proton channel, and keep the imaging areas and profiles of two nuclear channels highly matched. In this study, a hybrid monopole/loop technique was proposed for DT coil design and this technique was validated by implementing and testing a DT (1)H/(23)Na coil for MR imaging at 7T. The RF fields of the monopole ((1)H channel) and regular L/C loop ((23)Na channel) were orthogonal and intrinsically EM decoupled. Bench measurement results demonstrated the isolation between the two nuclear channels was better than -28 dB at both nuclear frequencies. Compared with the conventional DT coil using trap circuits, the monopole/loop DT coil had higher MR sensitivity for sodium imaging. The experimental results indicated that the monopole/loop technique might be a simple and efficient design for multinuclear imaging at ultrahigh fields. Additionally, the proposed DT coils based on the monopole/loop technique can be used as building blocks in designing multichannel DT coil arrays.
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Affiliation(s)
- Xinqiang Yan
- 1 State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China ; 2 Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China ; 3 Beijing Engineering Research Center of Radiographic Techniques and Equipment, Beijing 100049, China ; 4 Beijing Institute for Brain Disorders, Beijing 100053, China ; 5 Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California 94158, USA ; 6 UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco, California 94158, USA
| | - Rong Xue
- 1 State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China ; 2 Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China ; 3 Beijing Engineering Research Center of Radiographic Techniques and Equipment, Beijing 100049, China ; 4 Beijing Institute for Brain Disorders, Beijing 100053, China ; 5 Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California 94158, USA ; 6 UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco, California 94158, USA
| | - Xiaoliang Zhang
- 1 State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China ; 2 Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China ; 3 Beijing Engineering Research Center of Radiographic Techniques and Equipment, Beijing 100049, China ; 4 Beijing Institute for Brain Disorders, Beijing 100053, China ; 5 Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California 94158, USA ; 6 UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco, California 94158, USA
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20
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Lohezic M, Bollensdorff C, Korn M, Lanz T, Grau V, Kohl P, Schneider JE. Optimized radiofrequency coil setup for MR examination of living isolated rat hearts in a horizontal 9.4T magnet. Magn Reson Med 2014; 73:2398-405. [PMID: 25045897 DOI: 10.1002/mrm.25369] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Revised: 06/12/2014] [Accepted: 06/24/2014] [Indexed: 12/12/2022]
Abstract
PURPOSE (i) To optimize an MR-compatible organ perfusion setup for the nondestructive investigation of isolated rat hearts by placing the radiofrequency (RF) coil inside the perfusion chamber; (ii) to characterize the benefit of this system for diffusion tensor imaging and proton ((1) H-) MR spectroscopy. METHODS Coil quality assessment was conducted both on the bench, and in the magnet. The benefit of the new RF-coil was quantified by measuring signal-to-noise ratio (SNR), accuracy, and precision of diffusion tensor imaging/error in metabolite amplitude estimation, and compared to an RF-coil placed externally to the perfusion chamber. RESULTS The new design provided a 59% gain in signal-to-noise ratio on a fixed rat heart compared to using an external resonator, which found reflection in an improvement of living heart data quality, compared to previous external resonator studies. This resulted in 14-29% improvement in accuracy and precision of diffusion tensor imaging. The Cramer-Rao lower bounds for metabolite amplitude estimations were up to 5-fold smaller. CONCLUSION Optimization of MR-compatible perfusion equipment advances the study of rat hearts with improved signal-to-noise ratio performance, and thus improved accuracy/precision.
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Affiliation(s)
- Maelene Lohezic
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Christian Bollensdorff
- National Heart and Lung Institute, Imperial College London, London, UK.,Qatar Cardiovascular Research Center, Qatar Foundation, Doha, Qatar
| | | | | | - Vicente Grau
- Department of Engineering Science, University of Oxford, Oxford, UK
| | - Peter Kohl
- National Heart and Lung Institute, Imperial College London, London, UK.,Department of Computer Science, University of Oxford, Oxford, UK
| | - Jürgen E Schneider
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
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21
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Dardzinski BJ, Schneider E. Radiofrequency (RF) coil impacts the value and reproducibility of cartilage spin-spin (T2) relaxation time measurements. Osteoarthritis Cartilage 2013; 21:710-20. [PMID: 23376528 DOI: 10.1016/j.joca.2013.01.006] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Revised: 12/08/2012] [Accepted: 01/12/2013] [Indexed: 02/02/2023]
Abstract
INTRODUCTION T2 (spin-spin) relaxation time is frequently used for compositional assessment of articular cartilage. However little is known about the influence of magnetic resonance (MR) system components on these measurements. The reproducibility and range of cartilage T2 values were evaluated using different extremity radiofrequency (RF) coils with potential differences in flip angle uniformity and signal-to-noise ratio (SNR). METHOD Ten knees underwent 3 T MR exams using RF coils with different SNR: quadrature transmit/receive (QTR); quadrature transmit/eight-channel phased-array receive (QT8PAR). Each knee was scanned twice per coil (four exams total). T2 values were calculated for the central medial and lateral femoral (cMF, cLF) and medial and lateral tibial (MT, LT) cartilage. RESULTS The flip angle varied across a central 40 mm diameter region-of-interest of each coil by <1.5%. However SNR was significantly higher using QT8PAR than QTR (P < 0.001). T2 values for cMF (50.7 msec/45.9 msec) and MT (48.2 msec/41.6 msec) were significantly longer with QT8PAR than QTR (P < 0.05). T2 reproducibility was improved using QT8PAR for cMF and cLF (4.8%/5.8% and 4.1%/6.5%; P < 0.001), similar for LT (3.8%/3.6%; P = 1.0), and worse for MT (3.7%/3.3%; P < 0.001). T2 varied spatially, with cLF having the longest (52.0 msec) and the LT having the shortest (40.6 msec) values. All deep cartilage had significantly longer, and less variable, T2 values using QT8PAR (higher SNR; P < 0.03). CONCLUSIONS SNR varied spatially (significant) depending upon coil, but refocusing flip angle only slightly. With higher SNR, significantly longer T2 values were measured for deep (all plates) and global (MT, cMF) cartilage. T2 values varied by depth and plate, in agreement with prior studies.
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