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Wilcox M, Ogier S, Cheshkov S, Dimitrov I, Malloy C, Wright S, McDougall M. A 16-Channel 13C Array Coil for Magnetic Resonance Spectroscopy of the Breast at 7T. IEEE Trans Biomed Eng 2021; 68:2036-2046. [PMID: 33651680 DOI: 10.1109/tbme.2021.3063061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
OBJECTIVE Considering the reported elevation of ω-6/ω-3 fatty acid ratios in breast neoplasms, one particularly important application of 13C MRS could be in more fully understanding the breast lipidome's relationship to breast cancer incidence. However, the low natural abundance and gyromagnetic ratio of the 13C isotope lead to detection sensitivity challenges. Previous 13C MRS studies have relied on the use of small surface coils with limited field-of-view and shallow penetration depths to achieve adequate signal-to-noise ratio (SNR), and the use of receive array coils is still mostly unexplored. METHODS This work presents a unilateral breast 16-channel 13C array coil and interfacing hardware designed to retain the surface sensitivity of a single small loop coil while improving penetration depth and extending the field-of-view over the entire breast at 7T. The coil was characterized through bench measurements and phantom 13C spectroscopy experiments. RESULTS Bench measurements showed receive coil matching better than -17 dB and average preamplifier decoupling of 16.2 dB with no evident peak splitting. Phantom MRS studies show better than a three-fold increase in average SNR over the entirety of the breast region compared to volume coil reception alone as well as an ability for individual array elements to be used for coarse metabolite localization without the use of single-voxel or spectroscopic imaging methods. CONCLUSION Our current study has shown the benefits of the array. Future in vivo lipidomics studies can be pursued. SIGNIFICANCE Development of the 16-channel breast array coil opens possibilities of in vivo lipidomics studies to elucidate the link between breast cancer incidence and lipid metabolics.
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Qian W, Yu X, Qian C. Wireless Powered Encoding and Broadcasting of Frequency Modulated Detection Signals. IEEE ACCESS : PRACTICAL INNOVATIONS, OPEN SOLUTIONS 2020; 8:200450-200460. [PMID: 33828933 PMCID: PMC8023641 DOI: 10.1109/access.2020.3035938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Wireless transmission of locally detected RF signals is necessary for long-term operation of batteryless and embedded transducers. To improve signal transmission efficiency over larger distances, multi-stage circuits were employed to down-convert RF signals before encoding them onto the emitted carrier wave. Such multi-stage arrangement had complicated design and high-power consumption. Here, a compact and low-power wireless modulator is introduced to directly encode input RF signals onto its oscillation carrier wave. The modulator consists of a double frequency parametric resonator that is overlaid with a single frequency passive resonator to create three resonance modes. By properly adjusting the substrate thickness between resonators, the highest resonance frequency is tuned to approximately the sum of lower two resonance frequencies, enabling efficient conversion of wireless pumping power into sustained oscillation currents. When an input RF signal is present with a certain frequency offset, the oscillation signal can be frequency modulated by the input signal to create multiple modulation sidebands separated by the offset frequency. The frequency encoded carrier wave can transmit MRI signals over larger distance separations to maintain constant image sensitivity, making the modulator useful to improve the remote detectability of miniaturized implantable and interventional devices.
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Affiliation(s)
- Wei Qian
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824, USA
| | - Xin Yu
- Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA
| | - Chunqi Qian
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824, USA
- Department of Radiology, Michigan State University, East Lansing, MI 48824, USA
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Qian W, Yu X, Qian C. Wireless Reconfigurable RF Detector Array for Focal and Multiregional Signal Enhancement. IEEE ACCESS : PRACTICAL INNOVATIONS, OPEN SOLUTIONS 2020; 8:136594-136604. [PMID: 33747678 PMCID: PMC7971173 DOI: 10.1109/access.2020.3011905] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Wirelessly Amplified NMR Detectors (WAND) can utilize wireless pumping power to amplify MRI signals in situ for sensitivity enhancement of deep-lying tissues that are difficult to access by conventional surface coils. To reconfigure between selective and simultaneous activation in a multielement array, each WAND has a dipole resonance mode for MR signal acquisition and two butterfly modes that support counter-rotating current circulation. Because detectors in the same row share the same lower butterfly frequency but different higher butterfly frequency, a pumping signal at the sum frequency of the dipole mode and the higher butterfly mode can selectively activate individual resonators, leading to 4-fold sensitivity gain over passive coupling. Meanwhile, a pumping signal at the sum frequency of the dipole mode and the lower butterfly mode can simultaneously activate multiple resonators in the same row, leading to 3-fold sensitivity gain over passive coupling. When multiple rows of detectors are parallelly aligned, each row has a unique lower butterfly frequency for consecutive activation during the acquisition interval of the others. This wireless detector array can be embedded beneath a headpost that is normally required for multi-modal brain imaging, enabling easy reconfiguration between focal imaging of individual vessels and multiregional mapping of brain connectivity.
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Affiliation(s)
- Wei Qian
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824, USA
| | - Xin Yu
- Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA
| | - Chunqi Qian
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824, USA
- Department of Radiology, Michigan State University, East Lansing, MI 48824, USA
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Timilsina R, Qian C. Parallel magnetic resonance image reconstruction from a single-element parametric amplifier. Magn Reson Imaging 2019; 63:147-154. [PMID: 31425798 PMCID: PMC6861694 DOI: 10.1016/j.mri.2019.08.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 07/22/2019] [Accepted: 08/15/2019] [Indexed: 11/30/2022]
Abstract
In magnetic resonance imaging (MRI), acquisition speed is always an important issue. In this paper, we propose a promising technique to achieve parallel MRI (pMRI) on a single-channel spectrometer, using a novel Wireless Amplified Nuclear MR Detector (WAND) for spatial encoding in image reconstruction. For this, a planar structure double frequency WAND is designed and fabricated, where two of its frequencies - 'signal', ω1 and 'idler', ω2 are effectively utilized as two separate "channels" for accelerated acquisition. We provided a thorough background needed for the method and subsequently parallel imaging algorithms. Sum-of-Squares (SoS) reconstruction and GeneRalized Autocalibrating Partially Parallel Acquisition (GRAPPA) reconstruction are used to reconstruct as well as to analyze the SNR in the resulting images and validate our hypothesis. Experimental results using phantom datasets demonstrate that the proposed method of parallel imaging yield a better sensitivity for the combined images ('idler' + 'signal') than the sensitivity acquired for each individual image and thus significantly improving the reconstruction quality with optimal signal-to-noise ratio. We also demonstrated the achievable acceleration factor of this approach.
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Affiliation(s)
- Roshan Timilsina
- Department of Physics, Oakland University, Rochester, MI 48309, USA; Department of Radiology, Michigan State University, East Lansing, MI 48824, USA
| | - Chunqi Qian
- Department of Physics, Oakland University, Rochester, MI 48309, USA; Department of Radiology, Michigan State University, East Lansing, MI 48824, USA.
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Avdievich NI, Giapitzakis IA, Bause J, Shajan G, Scheffler K, Henning A. Double-row 18-loop transceive-32-loop receive tight-fit array provides for whole-brain coverage, high transmit performance, and SNR improvement near the brain center at 9.4T. Magn Reson Med 2018; 81:3392-3405. [PMID: 30506725 DOI: 10.1002/mrm.27602] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 09/12/2018] [Accepted: 10/19/2018] [Indexed: 11/06/2022]
Abstract
PURPOSE To improve the transmit (Tx) and receive (Rx) performance of a human head array and provide whole-brain coverage at 9.4T, a novel 32-element array design was developed, constructed, and tested. METHODS The array consists of 18 transceiver (TxRx) surface loops and 14 Rx-only vertical loops all placed in a single layer. The new design combines benefits of both TxRx and transmit-only-receive-only (ToRo) designs. The general idea of the design is that the total number of array elements (both TxRx and Rx) should not exceed the number of required Rx elements. First, the necessary number of TxRx loops is placed around the object tightly to optimize the Tx performance. The rest of the elements are loops, which are used only for reception. We also compared the performance of the new array with that of a state-of-the-art ToRo array consisting of 16 Tx-only loops and 31 Rx-only loops. RESULTS The new array provides whole-brain coverage, ~1.5 times greater Tx efficiency and 1.3 times higher SNR near the brain center as compared to the ToRo array, while the latter delivers higher (up to 1.5 times) peripheral SNR. CONCLUSION In general, the new approach of constructing a single-layer array consisting of both TxRx- and Rx-only elements simplifies the array construction by minimizing the total number of elements and makes the entire design more robust and, therefore, safe. Overall, our work provides a recipe for a Tx- and Rx-efficient head array coil suitable for parallel transmission and reception as well as whole-brain imaging at UHF.
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Affiliation(s)
- Nikolai I Avdievich
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Ioannis-Angelos Giapitzakis
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.,Graduate School of Neural and Behavioral Sciences, Tübingen, Germany
| | - Jonas Bause
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.,Graduate School of Neural and Behavioral Sciences, Tübingen, Germany
| | - Gunamony Shajan
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.,Institute of Neuroscience and Psychology, University of Glasgow, Glasgow, United Kingdom
| | - Klaus Scheffler
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.,Department for Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany
| | - Anke Henning
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
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Avdievich NI, Giapitzakis IA, Pfrommer A, Borbath T, Henning A. Combination of surface and 'vertical' loop elements improves receive performance of a human head transceiver array at 9.4 T. NMR IN BIOMEDICINE 2018; 31:e3878. [PMID: 29244225 DOI: 10.1002/nbm.3878] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 10/26/2017] [Accepted: 11/13/2017] [Indexed: 06/07/2023]
Abstract
Ultra-high-field (UHF, ≥7 T) human magnetic resonance imaging (MRI) provides undisputed advantages over low-field MRI (≤3 T), but its development remains challenging because of numerous technical issues, including the low efficiency of transmit (Tx) radiofrequency (RF) coils caused by the increase in tissue power deposition with frequency. Tight-fit human head transceiver (TxRx) arrays improve Tx efficiency in comparison with Tx-only arrays, which are larger in order to fit multi-channel receive (Rx)-only arrays inside. A drawback of the TxRx design is that the number of elements in an array is limited by the number of available high-power RF Tx channels (commonly 8 or 16), which is not sufficient for optimal Rx performance. In this work, as a proof of concept, we developed a method for increasing the number of Rx elements in a human head TxRx surface loop array without the need to move the loops away from a sample, which compromises the array Tx performance. We designed and constructed a prototype 16-channel tight-fit array, which consists of eight TxRx surface loops placed on a cylindrical holder circumscribing a head, and eight Rx-only vertical loops positioned along the central axis (parallel to the magnetic field B0 ) of each TxRx loop, perpendicular to its surface. We demonstrated both experimentally and numerically that the addition of the vertical loops has no measurable effect on the Tx efficiency of the array. An increase in the maximum local specific absorption rate (SAR), evaluated using two human head voxel models (Duke and Ella), measured 3.4% or less. At the same time, the 16-element array provided 30% improvement of central signal-to-noise ratio (SNR) in vivo relative to a surface loop eight-element array. The novel array design also demonstrated an improvement in the parallel Rx performance in the transversal plane. Thus, using this method, both the Rx and Tx performance of the human head array can be optimized simultaneously.
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Affiliation(s)
- N I Avdievich
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
- Institute of Physics, Ernst-Moritz-Arndt University Greifswald, Greifswald, Germany
| | - I A Giapitzakis
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
- Graduate School of Neural and Behavioral Sciences, Tübingen, Germany
| | - A Pfrommer
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - T Borbath
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - A Henning
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
- Institute of Physics, Ernst-Moritz-Arndt University Greifswald, Greifswald, Germany
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Yoon JH, Lee JM, Yu MH, Kim EJ, Han JK, Choi BI. High-resolution T1-weighted gradient echo imaging for liver MRI using parallel imaging at high-acceleration factors. ACTA ACUST UNITED AC 2014; 39:711-21. [DOI: 10.1007/s00261-014-0099-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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He W, Qin X, Jiejing R, Gengying L. Four-channel magnetic resonance imaging receiver using frequency domain multiplexing. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2007; 78:015102. [PMID: 17503941 DOI: 10.1063/1.2424426] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
An alternative technique that uses frequency domain multiplexing to acquire phased array magnetic resonance images is discussed in detail. The proposed method has advantages over traditional independent receiver chains in that it utilizes an analog-to-digital converter and a single-chip multicarrier receiver with high performance to reduce the size and cost of the phased array receiver system. A practical four-channel digital receiver using frequency domain multiplexing was implemented and verified on a home-built 0.3 T magnetic resonance imaging system. The experimental results confirmed that the cross talk between each channel was below -60 dB, the phase fluctuations were about 1 degrees , and there was no obvious signal-to-noise ratio degradation. It is demonstrated that the frequency domain multiplexing is a valuable and economical technique, particularly for array coil systems where the multichannel receiver is indispensable and dynamic range is not a critical problem.
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Affiliation(s)
- Wang He
- Shanghai Key Laboratory of Functional Magnetic Resonance Imaging, East China Normal University, Shanghai 200062, People's Republic of China
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Beuf O, Jaillon F, Saint-Jalmes H. Small-animal MRI: signal-to-noise ratio comparison at 7 and 1.5 T with multiple-animal acquisition strategies. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2006; 19:202-8. [PMID: 16957937 DOI: 10.1007/s10334-006-0048-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2006] [Accepted: 08/01/2006] [Indexed: 10/24/2022]
Abstract
OBJECTIVE The purpose of this study was to compare the signal-to-noise ratio (SNR) of phantom and rat brain images performed at 1.5 T on a clinical MR system and at 7 T on a small-animal experimental system. Comparison was carried out by taking into account SNR values based on a single sample acquisition at 1.5 and 7 T as well as on simultaneous imaging of multiple samples at 1.5 T. METHODS SNR was experimentally assessed on a phantom and rat brains at 1.5 and 7 T using 25 mm surface coils and compared to theoretical SNR gain estimations. The feasibility of multiple-animal imaging, using the hardware capabilities available on the 1.5 T system, was demonstrated. Finally, rat brain images obtained on a single animal at 7 T and on multiple animals acquired simultaneously at 1.5 T were compared. RESULTS Experimentally determined SNR at 7 T was far below theoretical estimations. Taking into account chemical shift, susceptibility artifacts and modifications of T1 and T2 relaxation times at higher field, a 7-T system holds limited advantage over a 1.5-T system. Instead, a multiple-animal acquisition methodology was demonstrated on a clinical 1.5-T scanner. This acquisition method significantly increases imaging efficiency and competes with single animal acquisitions at higher field. CONCLUSION Multiple-animal imaging using a standard clinical scanner has a great potential as a high-throughput acquisition method for small animals.
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Affiliation(s)
- Olivier Beuf
- Laboratoire de RMN, CNRS UMR 5012, Université Lyon1, ESCPE, 43 Boulevard du 11 Novembre 1918, 69616 Villeurbanne, France.
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Hadley JR, Roberts JA, Goodrich KC, Buswell HR, Parker DL. Relative RF coil performance in carotid imaging. Magn Reson Imaging 2005; 23:629-39. [PMID: 16051037 DOI: 10.1016/j.mri.2005.04.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2004] [Accepted: 04/11/2005] [Indexed: 11/17/2022]
Abstract
PURPOSE Computer simulations and measurements on human volunteers were used to test the extent to which the quality of carotid imaging might be improved by coil arrays that are not limited by a constraint on the number of RF coil receiver ports. METHODS Analytic near-field equations for the magnetic and electric fields of a rectangular loop resonator were used to estimate the relative signal-to-noise ratio (rSNR) along the length of a simulated carotid artery as a function of loop size, loop position and vessel depth. The sizes, positions and number of elements in a linear coil array that resulted in the maximum composite SNR along the length of a simulated carotid artery were then estimated. The linear array results were used to predict the total number of elements needed for optimal imaging of the carotid arteries. Also, three normal volunteers were imaged with a variety of RF coils, and the rSNR measurements along the lengths of the carotid artery were evaluated for each coil combination. RESULTS The analytic simulation and the human volunteer measurements both show that improved SNR (e.g., >300% at the bifurcation) can be obtained with coils tailored to each specific region of the carotid artery in comparison to that obtained with four-element arrays designed and used to image the entire carotid artery. CONCLUSIONS The resulting number of coil ports, 16 to 24, required for full coverage of the carotid arteries is consistent with the number of channels just becoming available on recently developed clinical scanners.
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Affiliation(s)
- J Rock Hadley
- Department of Radiology, Utah Center for Advanced Imaging Research, UCAIR, University of Utah, Salt Lake City, 84108, USA.
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Abstract
MRI faces fundamental limitations in terms of sensitivity and speed. These limitations can be effectively tackled by the transition to higher field strengths and parallel imaging technology. Owing to largely independent physics, the two approaches can be readily combined. Considering the specific advantages and disadvantages of high field strength and parallel imaging, it is found that the combination is particularly synergistic. In the joint approach, the two concepts play different roles. Higher field strength acts as a source of higher baseline signal-to-noise ratio (SNR), while parallelization acts as a means of converting added SNR into a variety of alternative benefits. This interplay holds promise for a broad range of clinical applications, as recently illustrated by several imaging studies at 3 T. As a consequence, clinical MRI at 3 T and higher is expected to rely more on parallel acquisition than at lower field strength. The specific synergy with parallel imaging may even make 3 T the field strength of choice for a range of exams that conventionally work best at 1.5 T or less.
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Affiliation(s)
- Klaas P Pruessmann
- Institute for Biomedical Engineering, University of Zurich and Swiss Federal Institute of Technology, Zurich, Switzerland.
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