1
|
Novel materials in magnetic resonance imaging: high permittivity ceramics, metamaterials, metasurfaces and artificial dielectrics. MAGNETIC RESONANCE MATERIALS IN PHYSICS, BIOLOGY AND MEDICINE 2022; 35:875-894. [PMID: 35471464 PMCID: PMC9596558 DOI: 10.1007/s10334-022-01007-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 02/18/2022] [Accepted: 03/07/2022] [Indexed: 11/01/2022]
Abstract
AbstractThis article reviews recent developments in designing and testing new types of materials which can be: (i) placed around the body for in vivo imaging, (ii) be integrated into a conventional RF coil, or (iii) form the resonator itself. These materials can improve the quality of MRI scans for both in vivo and magnetic resonance microscopy applications. The methodological section covers the basic operation and design of two different types of materials, namely high permittivity materials constructed from ceramics and artificial dielectrics/metasurfaces formed by coupled conductive subunits, either in air or surrounded by dielectric material. Applications of high permittivity materials and metasurfaces placed next to the body to neuroimaging and extremity imaging at 7 T, body and neuroimaging at 3 T, and extremity imaging at 1.5 T are shown. Results using ceramic resonators for both high field in vivo imaging and magnetic resonance microscopy are also shown. The development of new materials to improve MR image quality remains an active area of research, but has not yet found significant use in clinical applications. This is mainly due to practical issues such as specific absorption rate modelling, accurate and reproducible placement, and acceptable size/weight of such materials. The most successful area has been simple “dielectric pads” for neuroimaging at 7 T which were initially developed somewhat as a stop-gap while parallel transmit technology was being developed, but have continued to be used at many sites. Some of these issues can potentially be overcome using much lighter metasurfaces and artificial dielectrics, which are just beginning to be assessed.
Collapse
|
2
|
Okada T, Handa S, Ding B, Urayama SI, Fujimoto K, Shima A, Yoshii D, Ayaki T, Sawamoto N, Takahashi R, Onoe H, Isa T, Petropoulos L. Insertable inductively coupled volumetric coils for MR microscopy in a human 7T MR system. Magn Reson Med 2021; 87:1613-1620. [PMID: 34719801 PMCID: PMC9297907 DOI: 10.1002/mrm.29062] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 10/07/2021] [Accepted: 10/13/2021] [Indexed: 11/08/2022]
Abstract
PURPOSE To demonstrate the capability of insertable inductively coupled volumetric coils for MR microscopy in a human 7T MR system. METHODS Insertable inductively coupled volume coils with diameters of 26 and 64 mm (D26 and D64 coils) targeted for monkey and mouse brain specimen sizes were designed and fabricated. These coils were placed inside the imaging volume of a transmit/receive knee coil without wired connections to the main system. Signal-to-noise ratio (SNR) evaluations were conducted with and without the insertable coils, and the g-factor maps of parallel imaging (PI) were also calculated for the D64 coil. Brain specimens were imaged using 3D T 2 ∗ -weighted images with spatial resolution of isotropic 50 and 160 μm using D26 and D64 coils, respectively. RESULTS Relative average (SD) SNRs compared with knee coil alone were 12.54 (0.30) and 2.37 (0.05) at the center for the D26 and D64 coils, respectively. The mean g-factors of PI with the D64 coil for the factor of 2 were less than 1.1 in the left-right and anterior-posterior directions, and around 1.5 in the superior-inferior direction or when the PI factor of 3 was used. Acceleration in two directions showed lower g-factors but suffered from intrinsic low SNR. Representative T 2 ∗ -weighted images of the specimen showed structural details. CONCLUSION Inductively coupled small diameter coils insertable to the knee coil demonstrated high SNR and modest PI capability. The concept was successfully used to visualize fine structures of the brain specimen. The insertable coils are easy to handle and enable MR microscopy in a human whole-body 7T MRI system.
Collapse
Affiliation(s)
- Tomohisa Okada
- Human Brain Research Center, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Shinya Handa
- Quality Electrodynamics, Mayfield Village, Ohio, USA
| | - Bill Ding
- Quality Electrodynamics, Mayfield Village, Ohio, USA
| | - Shin-Ichi Urayama
- Human Brain Research Center, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Koji Fujimoto
- Human Brain Research Center, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Atsushi Shima
- Human Brain Research Center, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Daisuke Yoshii
- Department of Neurology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Takashi Ayaki
- Department of Neurology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Nobukatsu Sawamoto
- Department of Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Ryosuke Takahashi
- Department of Neurology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Hirotaka Onoe
- Human Brain Research Center, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Tadashi Isa
- Human Brain Research Center, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | | |
Collapse
|
3
|
Ceramic resonators for targeted clinical magnetic resonance imaging of the breast. Nat Commun 2020; 11:3840. [PMID: 32737293 PMCID: PMC7395080 DOI: 10.1038/s41467-020-17598-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Accepted: 06/25/2020] [Indexed: 12/02/2022] Open
Abstract
Currently, human magnetic resonance (MR) examinations are becoming highly specialized with a pre-defined and often relatively small target in the body. Conventionally, clinical MR equipment is designed to be universal that compromises its efficiency for small targets. Here, we present a concept for targeted clinical magnetic resonance imaging (MRI), which can be directly integrated into the existing clinical MR systems, and demonstrate its feasibility for breast imaging. The concept comprises spatial redistribution and passive focusing of the radiofrequency magnetic flux with the aid of an artificial resonator to maximize the efficiency of a conventional MR system for the area of interest. The approach offers the prospect of a targeted MRI and brings novel opportunities for high quality specialized MR examinations within any existing MR system. Here, the authors present a concept for targeted clinical magnetic resonance imaging for relatively small targets in the body. They use an artificial resonator for spatial redistribution and passive focusing of the radiofrequency magnetic flux and demonstrate feasibility for targeted breast imaging.
Collapse
|
4
|
Hosseinnezhadian S, Frass-Kriegl R, Goluch-Roat S, Pichler M, Sieg J, Vít M, Poirier-Quinot M, Darrasse L, Moser E, Ginefri JC, Laistler E. A flexible 12-channel transceiver array of transmission line resonators for 7 T MRI. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 296:47-59. [PMID: 30205313 DOI: 10.1016/j.jmr.2018.08.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 08/08/2018] [Accepted: 08/30/2018] [Indexed: 06/08/2023]
Abstract
A flexible transceiver array based on transmission line resonators (TLRs) combining the advantages of coil arrays with the possibility of form-fitting targeting cardiac MRI at 7 T is presented. The design contains 12 elements which are fabricated on a flexible substrate with rigid PCBs attached on the center of each element to place the interface components, i.e. transmit/receive (T/R) switch, power splitter, pre-amplifier and capacitive tuning/matching circuitry. The mutual coupling between elements is cancelled using a decoupling ring-based technique. The performance of the developed array is evaluated by 3D electromagnetic simulations, bench tests, and MR measurements using phantoms. Efficient inter-element decoupling is demonstrated in flat configuration on a box-shaped phantom (Sij < -19 dB), and bent on a human torso phantom (Sij < -16 dB). Acceleration factors up to 3 can be employed in bent configuration with reasonable g-factors (<1.7) in an ROI at the position of the heart. The array enables geometrical conformity to bodies within a large range of size and shape and is compatible with parallel imaging and parallel transmission techniques.
Collapse
Affiliation(s)
- Sajad Hosseinnezhadian
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria; MR Centre of Excellence, Medical University of Vienna, Lazarettgasse 14, 1090 Vienna, Austria; IR4M (Imagerie par Résonance Magnétique Médicale et Multi-Modalités), Bât 220, Univ. Paris-Sud, CNRS, Université Paris-Saclay, 91405 Orsay, France
| | - Roberta Frass-Kriegl
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria; MR Centre of Excellence, Medical University of Vienna, Lazarettgasse 14, 1090 Vienna, Austria
| | - Sigrun Goluch-Roat
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria; MR Centre of Excellence, Medical University of Vienna, Lazarettgasse 14, 1090 Vienna, Austria
| | - Michael Pichler
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria; MR Centre of Excellence, Medical University of Vienna, Lazarettgasse 14, 1090 Vienna, Austria
| | - Jürgen Sieg
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria; MR Centre of Excellence, Medical University of Vienna, Lazarettgasse 14, 1090 Vienna, Austria
| | - Martin Vít
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria; MR Centre of Excellence, Medical University of Vienna, Lazarettgasse 14, 1090 Vienna, Austria; IKEM (Institute for Clinical and Experimental Medicine), Vídeňská 1958/9, 140 21 Praha 4, Czech Republic
| | - Marie Poirier-Quinot
- IR4M (Imagerie par Résonance Magnétique Médicale et Multi-Modalités), Bât 220, Univ. Paris-Sud, CNRS, Université Paris-Saclay, 91405 Orsay, France
| | - Luc Darrasse
- IR4M (Imagerie par Résonance Magnétique Médicale et Multi-Modalités), Bât 220, Univ. Paris-Sud, CNRS, Université Paris-Saclay, 91405 Orsay, France
| | - Ewald Moser
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria; MR Centre of Excellence, Medical University of Vienna, Lazarettgasse 14, 1090 Vienna, Austria
| | - Jean-Christophe Ginefri
- IR4M (Imagerie par Résonance Magnétique Médicale et Multi-Modalités), Bât 220, Univ. Paris-Sud, CNRS, Université Paris-Saclay, 91405 Orsay, France
| | - Elmar Laistler
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria; MR Centre of Excellence, Medical University of Vienna, Lazarettgasse 14, 1090 Vienna, Austria.
| |
Collapse
|