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Puchnin V, Jandaliyeva A, Hurshkainen A, Solomakha G, Nikulin A, Petrova P, Lavrenteva A, Andreychenko A, Shchelokova A. Quadrature transceive wireless coil: Design concept and application for bilateral breast MRI at 1.5 T. Magn Reson Med 2023; 89:1251-1264. [PMID: 36336799 DOI: 10.1002/mrm.29507] [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: 04/21/2022] [Revised: 09/20/2022] [Accepted: 10/09/2022] [Indexed: 11/09/2022]
Abstract
PURPOSE Development of a novel quadrature inductively driven transceive wireless coil for breast MRI at 1.5 T. METHODS A quadrature wireless coil (HHMM-coil) design has been developed as a combination of two linearly polarized coils: a pair of 'metasolenoid' coils (MM-coil) and a pair of Helmholtz-type coils (HH-coil). The MM-coil consisted of an array of split-loop resonators. The HH-coil design included two electrically connected flat spirals. All the wireless coils were coupled to a whole-body birdcage coil. The HHMM-coil was studied and compared to the linear coils in terms of transmit and SAR efficiencies via numerical simulations. A prototype of HHMM-coil was built and tested on a 1.5 T scanner in a phantom and healthy volunteer. We also proposed an extended design of the HHMM-coil and compared its performance to a dedicated breast array. RESULTS Numerical simulations of the HHMM-coil with a female voxel model have shown more than a 2.5-fold increase in transmit efficiency and a 1.7-fold enhancement of SAR efficiency compared to the linearly polarized coils. Phantom and in vivo imaging showed good agreement with the numerical simulations. Moreover, the HHMM-coil provided good image quality, visualizing all areas of interest similar to a multichannel breast array with a 32% reduction in signal-to-noise ratio. CONCLUSION The proposed quadrature HHMM-coil allows the B 1 + $$ {\mathrm{B}}_1^{+} $$ -field to be significantly better focused in the region-of-interest compared to the linearly polarized coils. Thus, the HHMM-coil provides high-quality breast imaging on a 1.5 T scanner using a whole-body birdcage coil for transmit and receive.
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Affiliation(s)
- Viktor Puchnin
- School of Physics and Engineering, ITMO University, St. Petersburg, Russia
| | | | - Anna Hurshkainen
- School of Physics and Engineering, ITMO University, St. Petersburg, Russia
| | - Georgiy Solomakha
- School of Physics and Engineering, ITMO University, St. Petersburg, Russia
| | - Anton Nikulin
- School of Physics and Engineering, ITMO University, St. Petersburg, Russia
| | - Polina Petrova
- School of Physics and Engineering, ITMO University, St. Petersburg, Russia
| | - Anna Lavrenteva
- Medical Institute named after Berezin Sergey (MIBS), St. Petersburg, Russia
| | - Anna Andreychenko
- School of Physics and Engineering, ITMO University, St. Petersburg, Russia.,Research and Practical Clinical Center for Diagnostics and Telemedicine Technologies, Moscow Health Care Department, Moscow, Russia
| | - Alena Shchelokova
- School of Physics and Engineering, ITMO University, St. Petersburg, Russia
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Koloskov V, Zubkov M, Solomakha G, Puchnin V, Levchuk A, Efimtcev A, Melchakova I, Shchelokova A. Improving detection of fMRI activation at 1.5 T using high permittivity ceramics. J Magn Reson 2023; 348:107390. [PMID: 36774714 DOI: 10.1016/j.jmr.2023.107390] [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] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 01/27/2023] [Accepted: 01/29/2023] [Indexed: 06/18/2023]
Abstract
In this work, we propose an application of high permittivity materials (HPMs) to improve functional magnetic resonance imaging (fMRI) at 1.5 T, increasing the receive (Rx) sensitivity of a commercial multi-channel head coil. To evaluate the transmit efficiency, specific absorption rate (SAR), and the signal-to-noise ratio (SNR) changes introduced by the HPMs with relative permittivity of 4500, we considered the following configurations in simulation: a whole-body birdcage coil and an Rx-only multi-channel head coil with and without the HPM blocks in the presence of a homogeneous head phantom or a human body model. Experimental studies were also performed with a phantom and with volunteers. Seven healthy volunteers enrolled in a prospective study of fMRI activation in the motor cortex with and without HPMs. fMRI data were analyzed using group-level paired T-tests between acquisitions with and without HPM blocks. Both electromagnetic simulations and experimental measurements showed ∼25% improvement in the Rx sensitivity of a commercial head coil in the areas of interest when HPM blocks were placed in close proximity. It increased the detected motor cortex fMRI activation volume by an average of 56%, thus resulting in more sensitive functional imaging at 1.5 T.
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Affiliation(s)
- Vladislav Koloskov
- School of Physics and Engineering, ITMO University, St. Petersburg, Russian Federation
| | - Mikhail Zubkov
- School of Physics and Engineering, ITMO University, St. Petersburg, Russian Federation
| | - Georgiy Solomakha
- School of Physics and Engineering, ITMO University, St. Petersburg, Russian Federation
| | - Viktor Puchnin
- School of Physics and Engineering, ITMO University, St. Petersburg, Russian Federation
| | - Anatoliy Levchuk
- School of Physics and Engineering, ITMO University, St. Petersburg, Russian Federation; Department of Radiology, Federal Almazov North-West Medical Research Center, St. Petersburg, Russian Federation
| | - Alexander Efimtcev
- School of Physics and Engineering, ITMO University, St. Petersburg, Russian Federation; Department of Radiology, Federal Almazov North-West Medical Research Center, St. Petersburg, Russian Federation
| | - Irina Melchakova
- School of Physics and Engineering, ITMO University, St. Petersburg, Russian Federation
| | - Alena Shchelokova
- School of Physics and Engineering, ITMO University, St. Petersburg, Russian Federation.
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Brui E, Mikhailovskaya A, Solomakha G, Efimtcev A, Andreychenko A, Shchelokova A. Volumetric wireless coil for wrist MRI at 1.5 T as a practical alternative to Tx/Rx extremity coil: a comparative study. J Magn Reson 2022; 339:107209. [PMID: 35397309 DOI: 10.1016/j.jmr.2022.107209] [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] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 03/24/2022] [Accepted: 03/26/2022] [Indexed: 06/14/2023]
Abstract
This work performs a detailed assessment of radiofrequency (RF) safety and imaging performance of a volumetric wireless coil based on periodically coupled split-loop resonators (SLRs) for 1.5 T wrist MRI versus a commercially available transceive extremity coil. In particular, we evaluated the transmit efficiency and RF safety for three setups: a whole-body birdcage coil, a transceive extremity birdcage coil, and a volumetric wireless coil inductively coupled to the whole-body birdcage coil. The imaging performance of the two latter setups was studied experimentally for nine subjects. The signal-to-noise ratio (SNR) of the images acquired with several standard pulse sequences for osteoarthritis wrist imaging was assessed. Application of the wireless coil significantly improved the specific absorption rate (SAR) efficiency of the whole-body birdcage coil, with at least 4.3-fold and 7.6-fold improvement of local and global SAR efficiencies, respectively. This setup also outperformed the transceive extremity coil in terms of SNR (up to 1.40-fold gain) with a moderate (11%) reduction of the local SAR efficiency.
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Affiliation(s)
- Ekaterina Brui
- School of Physics and Engineering, ITMO University, St. Petersburg, Russia
| | - Anna Mikhailovskaya
- School of Physics and Engineering, ITMO University, St. Petersburg, Russia; School of Electrical Engineering, Tel Aviv University, Tel Aviv, Israel
| | - Georgiy Solomakha
- School of Physics and Engineering, ITMO University, St. Petersburg, Russia
| | - Alexander Efimtcev
- School of Physics and Engineering, ITMO University, St. Petersburg, Russia; Department of Radiology, Federal Almazov North-West Medical Research Center, St. Petersburg, Russia
| | - Anna Andreychenko
- School of Physics and Engineering, ITMO University, St. Petersburg, Russia; Research and Practical Clinical Center for Diagnostics and Telemedicine Technologies of the Moscow Health Care Department, Moscow, Russia
| | - Alena Shchelokova
- School of Physics and Engineering, ITMO University, St. Petersburg, Russia.
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Avdievich NI, Solomakha G, Ruhm L, Henning A, Scheffler K. 9.4 T double-tuned 13 C/ 1 H human head array using a combination of surface loops and dipole antennas. NMR Biomed 2021; 34:e4577. [PMID: 34169590 DOI: 10.1002/nbm.4577] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [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: 03/15/2021] [Revised: 05/17/2021] [Accepted: 06/02/2021] [Indexed: 06/13/2023]
Abstract
MRI at ultra-high field (UHF, ≥7 T) provides a natural strategy for improving the quality of X-nucleus magnetic resonance spectroscopy and imaging due to the intrinsic benefit of increased signal-to-noise ratio. Considering that RF coils require both local transmission and reception at UHF, the designs of double-tuned coils, which often consist of several layers of transmit and receive resonant elements, become quite complex. A few years ago, a new type of RF coil, ie a dipole antenna, was developed and used for human body and head imaging at UHF. Due to the mechanical and electrical simplicity of dipole antennas, combining an X-nucleus surface loop array with 1 H dipoles can substantially simplify the design of a double-tuned UHF human head array coil. Recently, we developed a novel bent folded-end dipole transceiver array for human head imaging at 9.4 T. The new eight-element dipole array demonstrated full brain coverage, and transmit efficiency comparable to that of the substantially more complex 16-element surface loop array. In this work, we developed, constructed and evaluated a double-tuned 13 C/1 H human head 9.4 T array consisting of eight 13 C transceiver surface loops and eight 1 H transceiver bent folded-end dipole antennas all placed in a single layer. We showed that interaction between loops and dipoles can be minimized by placing four 1 H traps into each 13 C loop. The presented double-tuned RF array coil substantially simplifies the design as compared with the common double-tuned surface loop arrays. At the same time, the coil demonstrated an improved 1 H longitudinal coverage and good transmit efficiency.
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Affiliation(s)
- Nikolai I Avdievich
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Georgiy Solomakha
- Department of Physics and Engineering, ITMO University, St. Petersburg, Russia
| | - Loreen Ruhm
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Anke Henning
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Klaus Scheffler
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
- Department for Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany
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Avdievich NI, Solomakha G, Ruhm L, Nikulin AV, Magill AW, Scheffler K. Folded-end dipole transceiver array for human whole-brain imaging at 7 T. NMR Biomed 2021; 34:e4541. [PMID: 33978270 DOI: 10.1002/nbm.4541] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [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: 03/01/2021] [Revised: 04/07/2021] [Accepted: 04/26/2021] [Indexed: 06/12/2023]
Abstract
The advancement of clinical applications of ultrahigh field (UHF) MRI depends heavily on advances in technology, including the development of new radiofrequency (RF) coil designs. Currently, the number of commercially available 7 T head RF coils is rather limited, implying a need to develop novel RF head coil designs that offer superior transmit and receive performance. RF coils to be used for clinical applications must be robust and reliable. In particular, for transmit arrays, if a transmit channel fails the local specific absorption rate may increase, significantly increasing local tissue heating. Recently, dipole antennas have been proposed and used to design UHF head transmit and receive arrays. The dipole provides a unique simplicity while offering comparable transmit efficiency and signal-to-noise ratio with the conventional loop design. Recently, we developed a novel array design in our laboratory using a folded-end dipole antenna. In this work, we developed, constructed and evaluated an eight-element transceiver bent folded-end dipole array for human head imaging at 7 T. Driven in the quadrature circularly polarized mode, the array demonstrated more than 20% higher transmit efficiency and significantly better whole-brain coverage than that provided by a widely used commercial array. In addition, we evaluated passive dipole antennas for decoupling the proposed array. We demonstrated that in contrast to the common unfolded dipole array, the passive dipoles moved away from the sample not only minimize coupling between the adjacent folded-end active dipoles but also produce practically no destructive interference with the quadrature mode of the array.
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Affiliation(s)
- Nikolai I Avdievich
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Georgiy Solomakha
- Department of Physics and Engineering, ITMO University, St. Petersburg, Russia
| | - Loreen Ruhm
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Anton V Nikulin
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
- Department for Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany
| | - Arthur W Magill
- Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Klaus Scheffler
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
- Department for Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany
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Avdievich NI, Solomakha G, Ruhm L, Henning A, Scheffler K. Unshielded bent folded-end dipole 9.4 T human head transceiver array decoupled using modified passive dipoles. Magn Reson Med 2021; 86:581-597. [PMID: 33629436 DOI: 10.1002/mrm.28711] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 01/14/2021] [Accepted: 01/14/2021] [Indexed: 11/10/2022]
Abstract
PURPOSE To develop an unshielded dipole transceiver array for human head imaging at 9.4 Tesla and to improve decoupling of adjacent dipole elements, a novel array design with modified passive dipole antennas was developed, evaluated, and tested. METHODS The new array consisted of 8 bent folded-end dipole elements placed in a single row and surrounding the head. Adjacent elements of RF transceiver arrays are usually decoupled by introducing circuits electrically connected to elements. These methods are difficult to use for dipole arrays because of the distant location of the adjacent antennas. A recently developed decoupling technique using passive dipoles is simple and does not require any electrical connection. However, common parallel passive dipoles can produce destructive interference with the RF field of the array itself. To minimize this interference, we placed the passive dipoles perpendicularly to the active dipoles and positioned them at the ends of the array. We also evaluated the effect of different passive dipoles on the array transmit performance. Finally, we optimized the array transmit performance by varying the length of the dipole folded portion. RESULTS By rotating the passive dipoles 90º and moving them toward the ends of the array, we minimized the destructive interference to an acceptable level without compromising decoupling and the transmit efficiency. CONCLUSION While keeping the benefits of the passive dipole decoupling method, the new modified dipoles produce substantially less destructive interference with the RF field of the array than the common design. The constructed transceiver array demonstrated good decoupling and whole-brain coverage.
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Affiliation(s)
- Nikolai I Avdievich
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Georgiy Solomakha
- Department of Physics and Engineering, ITMO University, St. Petersburg, Russia
| | - Loreen Ruhm
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Anke Henning
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.,Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Klaus Scheffler
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.,Department for Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany
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Solomakha G, Svejda JT, van Leeuwen C, Rennings A, Raaijmakers AJ, Glybovski S, Erni D. A self-matched leaky-wave antenna for ultrahigh-field magnetic resonance imaging with low specific absorption rate. Nat Commun 2021; 12:455. [PMID: 33469005 PMCID: PMC7815766 DOI: 10.1038/s41467-020-20708-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 12/09/2020] [Indexed: 01/16/2023] Open
Abstract
The technology of magnetic resonance imaging is developing towards higher magnetic fields to improve resolution and contrast. However, whole-body imaging at 7 T or even higher flux densities remains challenging due to wave interference, tissue inhomogeneities, and high RF power deposition. Nowadays, proper RF excitation of a human body in prostate and cardiac MRI is only possible to achieve by using phased arrays of antennas attached to the body (so-called surface coils). Due to safety concerns, the design of such coils aims at minimization of the local specific absorption rate (SAR), keeping the highest possible RF signal in the region of interest. Most previously demonstrated approaches were based on resonant structures such as e.g. dipoles, capacitively-loaded loops, TEM-line sections. In this study, we show that there is a better compromise between the transmit signal [Formula: see text] and the local SAR using non-resonant surface coils generating a low electric field in the proximity of their conductors. With this aim, we propose and experimentally demonstrate a leaky-wave antenna implemented as a periodically-slotted microstrip transmission line. Due to its non-resonant radiation, it induces only slightly over half the peak local SAR compared to a state-of-the-art dipole antenna but has the same transmit efficiency in prostate imaging at 7 T. Unlike other antennas for MRI, the leaky-wave antenna does not require to be tuned and matched when placed on a body, which makes it easy-to-use in prostate imaging at 7 T MRI.
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Affiliation(s)
- G Solomakha
- Department of Physics and Engineering, ITMO University, St. Petersburg, Russia
| | - J T Svejda
- General and Theoretical Electrical Engineering (ATE), Faculty of Engineering, University of Duisburg-Essen, and CENIDE - Center for Nanointegration Duisburg-Essen, Duisburg, Germany
| | - C van Leeuwen
- Imaging Division, UMC Utrecht, Utrecht, The Netherlands
| | - A Rennings
- General and Theoretical Electrical Engineering (ATE), Faculty of Engineering, University of Duisburg-Essen, and CENIDE - Center for Nanointegration Duisburg-Essen, Duisburg, Germany
| | - A J Raaijmakers
- Imaging Division, UMC Utrecht, Utrecht, The Netherlands.,Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - S Glybovski
- Department of Physics and Engineering, ITMO University, St. Petersburg, Russia.
| | - D Erni
- General and Theoretical Electrical Engineering (ATE), Faculty of Engineering, University of Duisburg-Essen, and CENIDE - Center for Nanointegration Duisburg-Essen, Duisburg, Germany
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Puchnin V, Solomakha G, Nikulin A, Magill AW, Andreychenko A, Shchelokova A. Metamaterial inspired wireless coil for clinical breast imaging. J Magn Reson 2021; 322:106877. [PMID: 33278812 DOI: 10.1016/j.jmr.2020.106877] [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] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 11/17/2020] [Accepted: 11/18/2020] [Indexed: 06/12/2023]
Abstract
In this work, we propose an application of a metamaterial inspired volumetric wireless coil (WLC) based on coupled split-loop resonators for targeted breast MRI at 1.5 T. Due to strong electromagnetic coupling with the body coil, the metamaterial inspired WLC locally focuses radiofrequency (RF) magnetic flux in the target region, thus improving both transmit and receive performance of the external body coil. This leads to substantial enhancement in local transmit efficiency and improvement of RF safety. Phantom images showed a tenfold increase of signal-to-noise ratio (SNR) in the region-of-interest (ROI) and, at the same time, an almost 50-fold reduction in transmit power relative to the same body coil used alone.
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Affiliation(s)
- Viktor Puchnin
- Department of Physics and Engineering, ITMO University, Saint Petersburg, Russia
| | - Georgiy Solomakha
- Department of Physics and Engineering, ITMO University, Saint Petersburg, Russia
| | - Anton Nikulin
- Institut Langevin, ESPCI Paris, CNRS, PSL University, Paris, France
| | - Arthur W Magill
- Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Anna Andreychenko
- Department of Physics and Engineering, ITMO University, Saint Petersburg, Russia; Research and Practical Clinical Center for Diagnostics and Telemedicine Technologies of the Moscow Health Care Department, Moscow, Russia
| | - Alena Shchelokova
- Department of Physics and Engineering, ITMO University, Saint Petersburg, Russia.
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Avdievich NI, Solomakha G, Ruhm L, Scheffler K, Henning A. Decoupling of folded-end dipole antenna elements of a 9.4 T human head array using an RF shield. NMR Biomed 2020; 33:e4351. [PMID: 32618047 DOI: 10.1002/nbm.4351] [Citation(s) in RCA: 5] [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: 03/03/2020] [Revised: 05/22/2020] [Accepted: 05/22/2020] [Indexed: 06/11/2023]
Abstract
Dipole antennas have recently been introduced to the field of MRI and successfully used, mostly as elements of ultra-high field (UHF, ≥ 7 T) human body arrays. Usage of dipole antennas for UHF human head transmit (Tx) arrays is still under development. Due to the substantially smaller size of the sample, dipoles must be made significantly shorter than in the body array. Additionally, head Tx arrays are commonly placed on the surface of rigid helmets made sufficiently large to accommodate tight-fit receive arrays. As a result, dipoles are not well loaded and are often poorly decoupled, which compromises Tx efficiency. Commonly, adjacent array elements are decoupled by circuits electrically connected to them. Placement of such circuits between distantly located dipoles is difficult. Alternatively, decoupling is provided by placing passive antennas between adjacent dipole elements. This method only works when these additional components are sufficiently small (compared with the size of active dipoles). Otherwise, RF fields produced by passive elements interfere destructively with the RF field of the array itself, and previously reported designs have used passive dipoles of about the size of array dipoles. In this work, we developed a novel method of decoupling for adjacent dipole antennas, and used this technique while constructing a 9.4 T human head eight-element transceiver array. Decoupling is provided without any additional circuits by simply folding the dipoles and using an RF shield located close to the folded portion of the dipoles. The array reported in this work demonstrates good decoupling and whole-brain coverage.
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Affiliation(s)
- Nikolai I Avdievich
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Georgiy Solomakha
- Department of Physics and Engineering, ITMO University, Saint Petersburg, Russia
| | - Loreen Ruhm
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - 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
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, USA
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Avdievich NI, Solomakha G, Ruhm L, Scheffler K, Henning A. Decoupling of folded-end dipole antenna elements of a 9.4 T human head array using an RF shield. NMR Biomed 2020. [PMID: 32618047 DOI: 10.1002/nbm.4351:e4351] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Dipole antennas have recently been introduced to the field of MRI and successfully used, mostly as elements of ultra-high field (UHF, ≥ 7 T) human body arrays. Usage of dipole antennas for UHF human head transmit (Tx) arrays is still under development. Due to the substantially smaller size of the sample, dipoles must be made significantly shorter than in the body array. Additionally, head Tx arrays are commonly placed on the surface of rigid helmets made sufficiently large to accommodate tight-fit receive arrays. As a result, dipoles are not well loaded and are often poorly decoupled, which compromises Tx efficiency. Commonly, adjacent array elements are decoupled by circuits electrically connected to them. Placement of such circuits between distantly located dipoles is difficult. Alternatively, decoupling is provided by placing passive antennas between adjacent dipole elements. This method only works when these additional components are sufficiently small (compared with the size of active dipoles). Otherwise, RF fields produced by passive elements interfere destructively with the RF field of the array itself, and previously reported designs have used passive dipoles of about the size of array dipoles. In this work, we developed a novel method of decoupling for adjacent dipole antennas, and used this technique while constructing a 9.4 T human head eight-element transceiver array. Decoupling is provided without any additional circuits by simply folding the dipoles and using an RF shield located close to the folded portion of the dipoles. The array reported in this work demonstrates good decoupling and whole-brain coverage.
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Affiliation(s)
- Nikolai I Avdievich
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Georgiy Solomakha
- Department of Physics and Engineering, ITMO University, Saint Petersburg, Russia
| | - Loreen Ruhm
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - 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
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, USA
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Avdievich NI, Solomakha G, Ruhm L, Bause J, Scheffler K, Henning A. Bent folded‐end dipole head array for ultrahigh‐field MRI turns “dielectric resonance” from an enemy to a friend. Magn Reson Med 2020; 84:3453-3467. [DOI: 10.1002/mrm.28336] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 04/16/2020] [Accepted: 05/03/2020] [Indexed: 11/05/2022]
Affiliation(s)
- Nikolai I. Avdievich
- High‐Field MR Center Max Planck Institute for Biological Cybernetics Tübingen Germany
| | - Georgiy Solomakha
- Department of Physics and Engineering ITMO University St. Petersburg Russia
| | - Loreen Ruhm
- High‐Field MR Center Max Planck Institute for Biological Cybernetics 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
| | - 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
- Advanced Imaging Research Center University of Texas Southwestern Medical Center Dallas TX USA
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Avdievich NI, Solomakha G, Ruhm L, Scheffler K, Henning A. Evaluation of short folded dipole antennas as receive elements of ultra‐high‐field human head array. Magn Reson Med 2019; 82:811-824. [DOI: 10.1002/mrm.27754] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 03/04/2019] [Accepted: 03/07/2019] [Indexed: 11/11/2022]
Affiliation(s)
- Nikolai I. Avdievich
- High‐Field MR Center, Max Planck Institute for Biological Cybernetics Tübingen Germany
| | - Georgiy Solomakha
- Department of Nanophotonics and Metamaterials ITMO University St. Petersburg Russia
| | - Loreen Ruhm
- High‐Field MR Center, Max Planck Institute for Biological Cybernetics Tübingen Germany
| | - 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
- Advanced Imaging Research Center University of Texas Southwestern Medical Center Dallas Texas
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Solomakha G, Andreychenko A, Moortele PFVD, Kroeze H, Raaijmakers AJ, Euwe FE, Lagendijk JJW, Luijten PR, Berg CATVD. A Coaxial RF Applicator for Ultra-High Field Human MRI. IEEE Trans Biomed Eng 2019; 66:2848-2854. [PMID: 30716028 DOI: 10.1109/tbme.2019.2897029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
OBJECTIVE To develop a novel radio-frequency (RF) concept for ultra-high field (UHF) human magnetic resonance imaging (MRI) based on a coaxial resonant cavity. METHODS A two-channel slotted coaxial cavity RF applicator was designed for human head MRI at 9.4T. Physical dimensions made the proposed conducting structure resonant at the required frequency without tuning lumped elements. Numerical electromagnetic modeling was used to optimize the design. RF safety was assessed with two representative human body models. MR experiments on a 9.4T scanner included gradient echo images and mapping of a circularly polarized RF magnetic field in the human head phantom. RESULTS The simulations and the phantom MR experiments agreed both qualitatively and quantitatively. The design was relatively simple, robust and required only a few additional reactive elements for the applicator's input impedance matching. The transmit efficiency and homogeneity of the excitation field were only 20% and 4% lower compared to a conventional 8-channel head array. CONCLUSION The coaxial RF applicator was feasible for human MRI at UHF and required no lumped elements for its tuning. Imaging performance of the RF applicator was only moderately lower compared to the conventional transmit array, but would be sufficient to provide an anatomical reference for the heteronuclei MRI. SIGNIFICANCE An alternative approach with the minimal involvement of lumped elements becomes feasible to design volume-type RF coils for UHF human MRI.
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Solomakha G, Leeuwen CV, Raaijmakers A, Simovski C, Popugaev A, Abdeddaim R, Melchakova I, Glybovski S. The dual‐mode dipole: A new array element for 7T body imaging with reduced SAR. Magn Reson Med 2018; 81:1459-1469. [PMID: 30226636 DOI: 10.1002/mrm.27485] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 07/05/2018] [Accepted: 07/14/2018] [Indexed: 01/13/2023]
Abstract
PURPOSE To design and test an RF-coil based on two orthogonal eigenmodes in a pair of coupled dipoles, for 7 Tesla body imaging with improved SAR, called dual-mode dipole. METHODS The proposed coil consists of two dipoles and creates two orthogonal field distributions in a sample (the even and odd modes). A coupler used to excite the modes was miniaturized with the conductor track routing technique. Numerical simulations of the dual-mode dipole in the presence of a homogeneous phantom were performed. Moreover, an array of such coils was simulated with a voxel body model. For comparison, a fractionated dipole combined with a surface loop coil was also simulated. Both coils were tested in a 7 Tesla MRI system on a phantom. Subsequently four dual-mode dipoles or dipole/loop combinations were used for a comparison of imaging performance in a human volunteer. RESULTS Using the even mode of the dual-mode dipole showed 70% SAR reduction in comparison to the fractionated dipole while having the same B 1 + in the prostate region. The odd mode of the dual-mode dipole showed a performance comparable to the surface loop both for SAR and B1 efficiency. The obtained results showed that the proposed coil while creating lower SAR gave images of the same quality as the reference coil. CONCLUSIONS It was demonstrated that the array of dual-mode dipoles provided the same SNR and prostate imaging quality as the reference array, while demonstrating lower SAR. This is due to a smoother current distribution over a sample surface.
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Affiliation(s)
- Georgiy Solomakha
- Department of Nanophotonics and Metamaterials ITMO University Saint Petersburg Russian Federation
| | - Carel van Leeuwen
- Department of Radiology University Medical Center Utrecht Utrecht The Netherlands
| | - Alexander Raaijmakers
- Department of Radiology University Medical Center Utrecht Utrecht The Netherlands
- Department of Biomedical Engineering Eindhoven University of Technology Eindhoven The Netherlands
| | - Constantin Simovski
- Department of Electronics and Nanoengineering Aalto University, School of Electrical Engineering Espoo Finland
| | - Alexander Popugaev
- RF and SatCom Systems Fraunhofer Institute for Integrated Circuits IIS Erlangen Germany
| | - Redha Abdeddaim
- Aix Marseille University, CNRS, Centrale Marseille, Institut Fresnel Marseille France
| | - Irina Melchakova
- Department of Nanophotonics and Metamaterials ITMO University Saint Petersburg Russian Federation
| | - Stanislav Glybovski
- Department of Nanophotonics and Metamaterials ITMO University Saint Petersburg Russian Federation
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