FR3128792A1 - Radiofrequency device for a magnetic resonance imaging system - Google Patents
Radiofrequency device for a magnetic resonance imaging system Download PDFInfo
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- FR3128792A1 FR3128792A1 FR2111500A FR2111500A FR3128792A1 FR 3128792 A1 FR3128792 A1 FR 3128792A1 FR 2111500 A FR2111500 A FR 2111500A FR 2111500 A FR2111500 A FR 2111500A FR 3128792 A1 FR3128792 A1 FR 3128792A1
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- 238000002595 magnetic resonance imaging Methods 0.000 title claims abstract description 32
- 239000003990 capacitor Substances 0.000 claims description 8
- 230000011218 segmentation Effects 0.000 claims description 4
- 230000003068 static effect Effects 0.000 claims description 4
- 238000000034 method Methods 0.000 claims description 2
- 238000003384 imaging method Methods 0.000 abstract description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 230000005415 magnetization Effects 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 230000002301 combined effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
- G01R33/36—Electrical details, e.g. matching or coupling of the coil to the receiver
- G01R33/3642—Mutual coupling or decoupling of multiple coils, e.g. decoupling of a receive coil from a transmission coil, or intentional coupling of RF coils, e.g. for RF magnetic field amplification
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
- G01R33/34—Constructional details, e.g. resonators, specially adapted to MR
- G01R33/34046—Volume type coils, e.g. bird-cage coils; Quadrature bird-cage coils; Circularly polarised coils
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
- G01R33/34—Constructional details, e.g. resonators, specially adapted to MR
- G01R33/34084—Constructional details, e.g. resonators, specially adapted to MR implantable coils or coils being geometrically adaptable to the sample, e.g. flexible coils or coils comprising mutually movable parts
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
- G01R33/36—Electrical details, e.g. matching or coupling of the coil to the receiver
- G01R33/3628—Tuning/matching of the transmit/receive coil
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
- G01R33/383—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field using permanent magnets
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
- G01R33/445—MR involving a non-standard magnetic field B0, e.g. of low magnitude as in the earth's magnetic field or in nanoTesla spectroscopy, comprising a polarizing magnetic field for pre-polarisation, B0 with a temporal variation of its magnitude or direction such as field cycling of B0 or rotation of the direction of B0, or spatially inhomogeneous B0 like in fringe-field MR or in stray-field imaging
Abstract
L’invention concerne un dispositif radiofréquence pour un système d’imagerie par résonance magnétique, le dispositif radiofréquence comprenant : - une bobine principale configurée pour transmettre une impulsion radiofréquence et recevoir des signaux radiofréquence ; - une bobine secondaire disposée intérieurement à la bobine principale, de sorte que la bobine primaire et la bobine secondaire soient couplées de manière inductive, la bobine secondaire formant par ailleurs un circuit passif. La bobine secondaire forme un chaussette souple destinée à être enfilée sur un corps ou une section d’un corps en vue de l’exécution d’une imagerie dudit corps par résonance magnétique. Figur e 2A radio frequency device for a magnetic resonance imaging system, the radio frequency device comprising: - a main coil configured to transmit a radio frequency pulse and receive radio frequency signals; - a secondary coil arranged inside the main coil, so that the primary coil and the secondary coil are coupled inductively, the secondary coil also forming a passive circuit. The secondary coil forms a flexible sock intended to be slipped over a body or a section of a body with a view to performing imaging of said body by magnetic resonance. Figure 2
Description
DOMAINE DE L’INVENTIONFIELD OF THE INVENTION
La présente invention se rapporte au domaine de l’imagerie par résonance magnétique. Plus particulièrement, la présente invention concerne un dispositif d’imagerie par résonance magnétique, et notamment un dispositif radiofréquence, permettant d’améliorer la qualité des images dès qu’un relativement faible champ magnétique statique doit être considéré.The present invention relates to the field of magnetic resonance imaging. More particularly, the present invention relates to a magnetic resonance imaging device, and in particular a radiofrequency device, making it possible to improve the quality of the images as soon as a relatively weak static magnetic field must be considered.
La présente invention trouve notamment son intérêt dès lors qu’il s’agit de considérer un système d’imagerie par résonance magnétique portable.The present invention finds particular interest when it comes to considering a portable magnetic resonance imaging system.
ARRIERE PLAN TECHNOLOGIQUE DE L’INVENTIONTECHNOLOGICAL BACKGROUND OF THE INVENTION
L'imagerie par résonance magnétique (IRM) est aujourd’hui largement mise en œuvre pour imager, de manière non invasive, l’intérieur de corps et notamment de corps humains. En particulier, l’imagerie par résonance magnétique permet de sonder les noyaux d’hydrogène, et notamment leur spin nucléaire, des molécules d’eau formant pour partie le corps sous examen.Magnetic resonance imaging (MRI) is now widely used to image, in a non-invasive way, the inside of bodies and in particular human bodies. In particular, magnetic resonance imaging makes it possible to probe the hydrogen nuclei, and in particular their nuclear spin, water molecules forming part of the body under examination.
A cet égard, un dispositif IRM est pourvu d’un aimant destiné à imposer au corps un champ magnétique statique (dit « champ magnétique principal »), sous l’effet duquel, les spins nucléaires associés aux noyaux d’hydrogène contenus dans les molécules d’eau formant pour partie ce corps se polarisent.In this respect, an MRI device is provided with a magnet intended to impose on the body a static magnetic field (called "main magnetic field"), under the effect of which, the nuclear spins associated with the hydrogen nuclei contained in the molecules of water forming part of this body become polarized.
Notamment, les moments magnétiques associés à ces spins s'alignent préférentiellement selon un axe, dit axe z, déterminé par l’orientation du champ magnétique principal de manière à créer une magnétisation du corps.In particular, the magnetic moments associated with these spins align preferentially along an axis, called the z axis, determined by the orientation of the main magnetic field so as to create magnetization of the body.
Un dispositif IRM comprend également des bobines à gradient configurées pour produire des champs magnétiques de petite amplitude et variant dans l'espace lorsqu'un courant leur est appliqué. Plus particulièrement, les bobines à gradient sont conçues pour produire une composante de champ magnétique qui est alignée parallèlement au champ magnétique principal, et qui varie linéairement en amplitude avec la position le long de l'un des axes x, y ou z (les axes x, y et z étant perpendiculaires deux à deux).An MRI device also includes gradient coils configured to produce small amplitude, spatially varying magnetic fields when current is applied thereto. Specifically, gradient coils are designed to produce a magnetic field component that is aligned parallel to the main magnetic field, and that varies linearly in magnitude with position along one of the x, y, or z axes (the axes x, y and z being perpendicular two by two).
Ainsi, les effets combinés des champ magnétiques imposés par les bobines à gradient permettent de coder spatialement chacune des positions du corps destiné à être sondé.Thus, the combined effects of the magnetic fields imposed by the gradient coils make it possible to spatially code each of the positions of the body intended to be probed.
Un dispositif IRM comprend également au moins une bobine radiofréquence (RF) destinée à jouer un rôle d’émetteur récepteur RF. Notamment, l’au moins une bobine radiofréquence est configurée pour émettre des impulsions d’énergie RF d’une fréquence égale ou voisine de la fréquence de résonance des spins des noyaux d’hydrogène et qui est au moins en partie absorbée par ces noyaux.An MRI device also includes at least one radio frequency (RF) coil intended to act as an RF transceiver. In particular, the at least one radiofrequency coil is configured to emit RF energy pulses of a frequency equal to or close to the resonance frequency of the spins of the hydrogen nuclei and which is at least partly absorbed by these nuclei.
Dès lors que l’émission RF est interrompue, les spins nucléaires relaxent afin de retrouver leur état d’énergie initial et émettent à leur tour un signal RF susceptible d’être collecté par au moins une bobine RF. Ce signal RF est ensuite traité à l’aide d’un ordinateur et d’algorithmes de reconstruction afin d’obtenir une image du corps.As soon as the RF emission is interrupted, the nuclear spins relax in order to regain their initial energy state and in turn emit an RF signal capable of being collected by at least one RF coil. This RF signal is then processed using a computer and reconstruction algorithms to obtain an image of the body.
Le champ magnétique principal, généralement compris entre 1,5 Tesla et 3 Tesla, permet d’atteindre des rapports de signal sur bruit relativement raisonnables et par voie de conséquence de former des images du corps humain d’une qualité suffisante sur des durées de l’ordre de la minute ou plus.The main magnetic field, generally between 1.5 Tesla and 3 Tesla, makes it possible to achieve relatively reasonable signal-to-noise ratios and consequently to form images of the human body of sufficient quality over periods of l order of the minute or more.
Toutefois, il est des circonstances pour lesquelles il n’est pas possible de mettre en œuvre un champ magnétique principal d’une telle intensité. Les dispositifs IRM portables en sont un exemple. Ces derniers comprennent en général un aimant permanent ou des électro-aimants d’une capacité limitée, et ne peuvent imposer un champ magnétique principal d’une intensité supérieure à 60 mT, voire supérieure à 200 mT, sans pénaliser la masse ou l’encombrement du dispositif IRM considéré.However, there are circumstances for which it is not possible to implement a main magnetic field of such intensity. One example is portable MRI devices. The latter generally include a permanent magnet or electromagnets of limited capacity, and cannot impose a main magnetic field with an intensity greater than 60 mT, or even greater than 200 mT, without penalizing the mass or the size. of the MRI device under consideration.
Cette limitation en termes d’intensité de champ magnétique principal affecte directement les performances du dispositif IRM. Notamment, les images obtenues avec un tel dispositif IRM sont susceptibles de présenter une qualité fortement dégradée par un rapport signal sur bruit défavorable. Ce rapport signal sur bruit défavorable est la conséquence de la forte diminution de l’aimantation présente dans les tissus du fait de la considération d’un champ magnétique principal de faible amplitude.This limitation in terms of main magnetic field intensity directly affects the performance of the MRI device. In particular, the images obtained with such an MRI device are likely to have a quality that is greatly degraded by an unfavorable signal-to-noise ratio. This unfavorable signal-to-noise ratio is the consequence of the strong reduction in the magnetization present in the tissues due to the consideration of a main magnetic field of low amplitude.
Un but de la présente invention est de proposer une bobine RF susceptible d’être mise en œuvre dans un dispositif IRM et permettant d’améliorer l’amplitude du signal reçu au sein du volume de ladite bobine RF.An object of the present invention is to provide an RF coil capable of being implemented in an MRI device and making it possible to improve the amplitude of the signal received within the volume of said RF coil.
Un autre but de la présente invention est de proposer une bobine RF présentant une sensibilité au bruit réduite au regard des bobines RF connues de l’état de la technique.Another object of the present invention is to provide an RF coil having reduced sensitivity to noise compared to the RF coils known from the state of the art.
Un autre but de la présente invention est de proposer un système IRM susceptible de fonctionner à faible champ magnétique principal, notamment d’une intensité inférieure à 100 mT, voire 50 mT.Another object of the present invention is to provide an MRI system capable of operating with a weak main magnetic field, in particular with an intensity of less than 100 mT, or even 50 mT.
Un autre but de la présente invention est de proposer un système IRM permettant une meilleure ergonomie pour un patient destiné à subir une examen avec ledit système IRM.Another object of the present invention is to propose an MRI system allowing better ergonomics for a patient intended to undergo an examination with said MRI system.
BREVE DESCRIPTION DE L’INVENTIONBRIEF DESCRIPTION OF THE INVENTION
La présente invention concerne un dispositif radiofréquence pour un système d’imagerie par résonance magnétique, le dispositif radiofréquence comprenant :The present invention relates to a radio frequency device for a magnetic resonance imaging system, the radio frequency device comprising:
- une bobine principale configurée pour transmettre une impulsion radiofréquence et recevoir des signaux radiofréquence ;- a main coil configured to transmit a radio frequency pulse and receive radio frequency signals;
- une bobine secondaire disposée coaxialement et intérieurement à la bobine principale, de sorte que la bobine primaire et la bobine secondaire soient couplées de manière inductive, la bobine secondaire formant par ailleurs un circuit passif.- a secondary coil arranged coaxially and internally to the main coil, so that the primary coil and the secondary coil are coupled inductively, the secondary coil also forming a passive circuit.
Cet agencement d’une bobine principale et d’une bobine secondaire, couplées de manière inductive, permet de former un dispositif radiofréquence qui présente un facteur de qualité supérieur à celui de la bobine principale prise seule. Ce dispositif peut alors avantageusement être mis en œuvre dans un système d’imagerie par résonnance magnétique afin d’améliorer le rapport signal sur bruit et par voie de conséquence la qualité des images.This arrangement of a main coil and a secondary coil, inductively coupled, makes it possible to form a radio frequency device which has a quality factor higher than that of the main coil taken alone. This device can then advantageously be implemented in a magnetic resonance imaging system in order to improve the signal-to-noise ratio and consequently the quality of the images.
Selon un mode de mise en œuvre, la bobine principale et la bobine secondaire présentent, respectivement, un diamètre principal D1 et un diamètre secondaire D2, le rapport du diamètre principal D1 sur le diamètre secondaire D2 étant compris entre 1,05 et 4.According to one mode of implementation, the main coil and the secondary coil have, respectively, a main diameter D1 and a secondary diameter D2, the ratio of the main diameter D1 to the secondary diameter D2 being between 1.05 and 4.
Selon un mode de mise en œuvre, la bobine principale et la bobine secondaire présentent, respectivement, une longueur principale L1 et une longueur secondaire L2, le rapport de la longueur principale L1 sur la longueur secondaire L2 étant compris entre 0,5 et 2.According to one mode of implementation, the main coil and the secondary coil have, respectively, a main length L1 and a secondary length L2, the ratio of the main length L1 to the secondary length L2 being between 0.5 and 2.
Selon un mode de mise en œuvre, la bobine principale comprend des condensateurs, dits condensateurs de segmentation principales.According to one mode of implementation, the main coil comprises capacitors, called main segmentation capacitors.
Selon un mode de mise en œuvre, la bobine secondaire comprend des condensateurs, dits condensateurs de segmentation secondaires.According to one mode of implementation, the secondary coil comprises capacitors, called secondary segmentation capacitors.
Selon un mode de mise en œuvre, ledit dispositif radiofréquence comprend en outre des moyens de génération d’impulsions radiofréquences, les moyens de génération d’impulsions radiofréquences étant adaptés pour imposer la circulation d’une impulsion de courant dans la bobine principale.According to one mode of implementation, said radiofrequency device further comprises means for generating radiofrequency pulses, the means for generating radiofrequency pulses being adapted to impose the circulation of a current pulse in the main coil.
Selon un mode de mise en œuvre, ledit dispositif radiofréquence comprend des moyens de traitement radiofréquence, les moyens de traitement radiofréquence étant adaptés pour traiter un signal radiofréquence susceptible d’être reçu par la bobine principale.According to one mode of implementation, said radiofrequency device comprises radiofrequency processing means, the radiofrequency processing means being adapted to process a radiofrequency signal likely to be received by the main coil.
Selon un mode de réalisation, la bobine secondaire forme un chaussette souple destinée à être enfilée sur un corps ou une section d’un corps en vue de l’exécution d’une imagerie dudit corps par résonance magnétique.According to one embodiment, the secondary coil forms a flexible sock intended to be slipped over a body or a section of a body with a view to performing imaging of said body by magnetic resonance.
L’invention concerne également système d’imagerie par résonance magnétique pourvu du dispositif radiofréquence selon la présente invention.The invention also relates to a magnetic resonance imaging system provided with the radiofrequency device according to the present invention.
Selon un mode de mise en œuvre, ledit système d’imagerie par résonance magnétique comprend un aimant définissant un espace à l’intérieur duquel le dispositif radiofréquence est disposé.According to one mode of implementation, said magnetic resonance imaging system comprises a magnet defining a space inside which the radiofrequency device is arranged.
Selon un mode de mise en œuvre, l’aimant est un aimant permanent, avantageusement, l’aimant permanent est susceptible de générer un champ magnétique statique inférieur à 100 mT, encore plus avantageusement inférieur à 50 mT.According to one mode of implementation, the magnet is a permanent magnet, advantageously the permanent magnet is capable of generating a static magnetic field of less than 100 mT, even more advantageously less than 50 mT.
Selon un mode de mise en œuvre, ledit système d’imagerie par résonance magnétique comprend également des bobines à gradient.According to one mode of implementation, said magnetic resonance imaging system also comprises gradient coils.
D’autres caractéristiques et avantages de l’invention ressortiront de la description détaillée qui va suivre en référence aux figures annexées sur lesquelles :Other characteristics and advantages of the invention will emerge from the detailed description which follows with reference to the appended figures in which:
Claims (12)
- une bobine principale (8) configurée pour transmettre une impulsion radiofréquence et recevoir des signaux radiofréquence ;
- une bobine secondaire (9) disposée intérieurement à la bobine principale (8), de sorte que la bobine primaire et la bobine secondaire (9) soient couplées de manière inductive, la bobine secondaire (9) formant par ailleurs un circuit passif.Radiofrequency device (7) for a magnetic resonance imaging system (1), the radiofrequency device (7) comprising:
- a main coil (8) configured to transmit a radio frequency pulse and to receive radio frequency signals;
- a secondary coil (9) arranged inside the main coil (8), so that the primary coil and the secondary coil (9) are coupled inductively, the secondary coil (9) also forming a passive circuit.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
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FR2111500A FR3128792A1 (en) | 2021-10-28 | 2021-10-28 | Radiofrequency device for a magnetic resonance imaging system |
PCT/EP2022/078511 WO2023072608A1 (en) | 2021-10-28 | 2022-10-13 | Radio frequency device for a magnetic resonance imaging system |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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FR2111500 | 2021-10-28 | ||
FR2111500A FR3128792A1 (en) | 2021-10-28 | 2021-10-28 | Radiofrequency device for a magnetic resonance imaging system |
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FR3128792A1 true FR3128792A1 (en) | 2023-05-05 |
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FR2111500A Pending FR3128792A1 (en) | 2021-10-28 | 2021-10-28 | Radiofrequency device for a magnetic resonance imaging system |
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FR (1) | FR3128792A1 (en) |
WO (1) | WO2023072608A1 (en) |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4680549A (en) * | 1984-01-20 | 1987-07-14 | Instrumentarium Corp. | NMR coil arrangement |
US5575287A (en) * | 1993-01-25 | 1996-11-19 | Fonar Corporation | Inductively coupled RF coils for magnetic resonance studies |
US6023166A (en) * | 1997-11-19 | 2000-02-08 | Fonar Corporation | MRI antenna |
US6157193A (en) * | 1997-11-18 | 2000-12-05 | Siemens Aktiengesellschaft | MR imaging system with electrically insulated coil element |
EP3368914B1 (en) | 2015-10-26 | 2021-06-30 | Antonello Sotgiu | Magnet assembly for mri comprising cylindrical rings of halbach type |
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2021
- 2021-10-28 FR FR2111500A patent/FR3128792A1/en active Pending
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2022
- 2022-10-13 WO PCT/EP2022/078511 patent/WO2023072608A1/en unknown
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4680549A (en) * | 1984-01-20 | 1987-07-14 | Instrumentarium Corp. | NMR coil arrangement |
US5575287A (en) * | 1993-01-25 | 1996-11-19 | Fonar Corporation | Inductively coupled RF coils for magnetic resonance studies |
US6157193A (en) * | 1997-11-18 | 2000-12-05 | Siemens Aktiengesellschaft | MR imaging system with electrically insulated coil element |
US6023166A (en) * | 1997-11-19 | 2000-02-08 | Fonar Corporation | MRI antenna |
EP3368914B1 (en) | 2015-10-26 | 2021-06-30 | Antonello Sotgiu | Magnet assembly for mri comprising cylindrical rings of halbach type |
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