WO2015187607A1 - Excitation harmonique de signal rm pour irm interventionnelle - Google Patents

Excitation harmonique de signal rm pour irm interventionnelle Download PDF

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Publication number
WO2015187607A1
WO2015187607A1 PCT/US2015/033652 US2015033652W WO2015187607A1 WO 2015187607 A1 WO2015187607 A1 WO 2015187607A1 US 2015033652 W US2015033652 W US 2015033652W WO 2015187607 A1 WO2015187607 A1 WO 2015187607A1
Authority
WO
WIPO (PCT)
Prior art keywords
coil
frequency
resonance frequency
diode element
receiver
Prior art date
Application number
PCT/US2015/033652
Other languages
English (en)
Inventor
Dmitri Artemov
Original Assignee
The Johns Hopkins University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by The Johns Hopkins University filed Critical The Johns Hopkins University
Publication of WO2015187607A1 publication Critical patent/WO2015187607A1/fr

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Classifications

    • 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
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
    • A61B5/055—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves  involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
    • 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
    • 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
    • G01R33/3635—Multi-frequency operation
    • 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

Definitions

  • the present invention relates generally to imaging technologies. More
  • the present invention relates to a system and method for generating harmonic excitation of magnetic resonance signal for interventional magnetic resonance imaging.
  • Interventional magnetic resonance imaging is used to guide minimally invasive procedures intra-operatively and interactively.
  • interventional MRI can be used for interventional procedures such as radiation treatment and surgery.
  • the present invention provides a system for imaging including an implantable RF coil configured to excite magnetic resonance (MR) signals in a subject.
  • the system includes an RF transmitter configured to generate an RF pulse field. Additionally, the system includes an RF receiver.
  • the RF coil further includes a non-linear diode element.
  • the non-linear diode element can take the form of a Schottky diode.
  • the RF coil in the "ground state” with the open non-linear diode element is tuned to a fraction of the MR resonance frequency, ⁇ 0 / ⁇ .
  • the RF coil in the "activated state” with the closed non- linear diode is tuned to the MR resonance frequency, ⁇ 0 .
  • the RF transmitter produces the RF pulse field at a low frequency, ⁇ 0 / ⁇ .
  • the RF receiver further comprises an MR receiver coil of a standard MR instrument, which is tuned to the MR resonance frequency, ⁇ 0 .
  • the RF transmitter produces an RF filed at half-resonance frequency.
  • a method for imaging includes implanting an RF coil configured to excite magnetic resonance (MR) signals in a subject.
  • the method includes transmitting an RF pulse field with an RF transmitter configured to generate the RF pulse field.
  • the method also includes receiving the RF pulse field with an RF receiver.
  • MR magnetic resonance
  • the method includes using the RF coil having a non-linear diode element.
  • the method includes using the RF coil having the non-linear diode element taking the form of a Schottky diode.
  • the non-linear diode element is tuned to the MR resonance frequency, ⁇ 0 , or alternately, the non-linear diode is tuned to a fraction of the MR resonance frequency, ⁇ 0 / ⁇ .
  • the RF pulse field is produced at a low frequency, ⁇ 0 / ⁇ .
  • the method includes using the RF receiver having an MR receiver coil of a standard MR instrument.
  • the method also includes producing a harmonic frequency ( ⁇ 0 / ⁇ ) •m with the RF coil during the RF pulse field at a frequency, ⁇ 0 / ⁇ , due to nonlinearity of the diode element in the RF coil.
  • the method includes producing an RF field at half-resonance frequency. Additionally, the method includes using two inductive parallel loops. The method can also include using a second harmonic generating microcoil.
  • FIG. 1 illustrates a schematic diagram of a second harmonic excitation MR experiment on a 9.4 T MR scanner, according to an embodiment of the present invention.
  • FIGS. 2A-2D illustrate a picture of and schematic diagrams of a second harmonic generating microcoil (SHMC) with a non-linear diode element, according to an embodiment of the present invention.
  • SHMC second harmonic generating microcoil
  • FIG. 3A illustrates a graphical view of a ID spectra obtained with a standard external volume RF coil and those excited by SHMC and detected by the standard coil are shown using arbitrary scaling, according to an embodiment of the present invention.
  • FIG. 4A illustrates a side view of an RF coil attached to a subject.
  • FIGS. 4B-4C illustrate images related to an in vivo second harmonic excitation MR experiment, according to an embodiment of the present invention.
  • the present invention is directed to a system and method for harmonic excitation of magnetic resonance (MR) signal for interventional MR imaging (MRI).
  • the system includes an implantable RF coil or a coil attached to an interventional device that excites MR signals in the subject, when driven by lower frequency RF filed from an external coil, due to nonlinearity of the diode element.
  • This approach permits detection of MR signal in close proximity of the inserted coil by a standard MRI receiver coil without background from the rest of the subject and thus provides precise position of the coil and/or location of the device on MR images.
  • the procedure allows obtaining localized MR images and spectra.
  • MR-detectable devices are important for interventional procedures, and should provide a clear imaging signature while not degrading diagnostic imaging quality.
  • the MR-detectable probe design is based on excitation of MR signals by high-frequency RF harmonics generated by the probe with a non-linear element.
  • the implantable RF coil is irradiated by the pulsed RF field at a low frequency ( ⁇ 0 In).
  • the harmonic resonance frequency ⁇ 0 generated during the RF pulse due to nonlinearity of the diode element, excites MR signals in a sample that can be detected by a standard MR receiver coil of a standard MR instrument.
  • Standard imaging and spectroscopy pulse sequences can be used to (i) produce highly localized spectra and/or images of the structures in the close proximity to the implantable RF coil and (ii) to determine spatial position of the implantable RF coil with high precision that is essential for interventional procedures.
  • the circuit in its "ground state" is not tuned to the coo resonance frequency there is no heat generation during a standard MRI performed at the resonance frequency ⁇ 0 on the subject with the inserted coil.
  • the present invention is directed to an implantable RF coil with a non- linear diode element designed to excite MR signals in the subject when radiated by RF filed from an external coil at low frequency equal to one-half of the magnetic resonance frequency.
  • Second harmonic generated in the coil by the nonlinear element is at the resonance frequency and produces MR signals in the subject in close proximity of the inserted coil that can be detected by a standard MRI receiver coil.
  • the method allows obtaining localized MR images and spectra and determining a precise position of the inserted coil within the subject that can be important for the design of MR guided probes for interventional procedures.
  • An implantable probe was designed to excite MR signals when driven by an external RF filed at half-resonance frequency.
  • SHMC FLASH images were acquired using square 500 RF pulses at 200 MHz and an RF power level of 35 dBm applied to the transmit coil.
  • MR harmonic imaging experiments were performed with an agarose phantom and with an experimental animal model with implanted SHMC.
  • the design and principle of operation of a second harmonic generating microcoil (SHMC) are shown in FIGS. 1 and 2A-2D.
  • the SHMC was constructed using two inductive parallel loops with diameters of 4 mm, connected by a 15 pF nonmagnetic capacitor, as shown in Fig. 2A.
  • a low barrier ( ⁇ 250 mV) and low capacity ( ⁇ 0.3 pF), Schottky diode (HSMS-2852, Avago Technologies) was inserted in the middle point of one of the loops.
  • the diode In the absence of RF excitation, the diode is open and the circuit is tuned at a resonance frequency of 200 MHz.
  • the diode is transiently closed by the direct voltage in the circuit, and the resonance frequency is shifted to 400 MHz, as shown in FIGS. 2B-2D.
  • a single-turn loop 200 MHz transmit coil was constructed with an LC trap filter blocking the 400 MHz frequency.
  • free induction decay at 400 MHz is produced by proton spins of the sample excited by the second harmonic generated by a microcoil with a non-linear diode element.
  • An ellipse surrounds a region of the sample where the MR signal is generated.
  • An important requirement is to position the transmitting RF coil parallel to the plane of SHMC to ensure good magnetic coupling between the coils.
  • the design and principle of operation of SHMC are shown in FIGS. 2A-2D.
  • the coil consists of two inductive loops with diameters of approximately 4 mm connected by a 15 pF non-magnetic ceramic chip capacitor.
  • One of the loops has a low barrier ( ⁇ 250 mV) and low capacity ( ⁇ 0.3 pF) high-frequency Schottky diode (such as HSMS-2852, Avago
  • the diode In the absence of RF excitation the diode is open and the circuit is tuned at a resonance frequency of 200 MHz. During the 200 MHz RF pulse the diode is transiently closed by the direct voltage generated in the circuit and the resonance frequency of the circuit with two parallel loops is shifted to 400 MHz. A 400 MHz second harmonic of the applied 200 MHz RF field excites nuclear magnetization of the protons in the sample to generate a free induction decay (FID) detected by the receiver system of the instrument.
  • FID free induction decay
  • FIGS. 2A-2D illustrate a picture and schematics of the SHMC and two different modes of operation.
  • FIG. 2 A illustrates an image of the SHMC, according to an embodiment of the present invention.
  • FIG. 2B illustrates a schematic diagram of the image shown in FIG. 2A.
  • FIGS. 2C and 2D illustrate two different modes of operation of the SHMC illustrated in FIG. 2B.
  • FIG. 2C illustrates the SHMC without an applied RF field at a resonance frequency of 200 MHz.
  • FIG. 2D illustrates an SHMC with an applied RF field at a resonance frequency of 400 MHz.
  • FIG. 3A A T2 MR image of the sample with embedded SHMC is shown in FIG. 3B, left. Magnetic susceptibility artifacts generated by the capacitor and the diode (slightly magnetic) are visible in the image.
  • FIG. 3B center A slice from a 3D gradient echo image generated by SHMC is shown in FIG. 3B center. Only sample areas next to the two loops of SHMC contribute to the detected MR signal.
  • FIG. 3B For comparison, a 3D reconstruction of gradient echo images obtained using a standard RF coil and SHMC with second harmonic excitation are shown in FIG. 3B, right.
  • a T2 MR image of a 3% agarose phantom prepared in a standard 10 mm NMR tube with the embedded SHMC (FIG. 2A) is shown in FIG. 3B. Magnetic susceptibility artifacts from the capacitor and the diode are visible in the image.
  • FIG. 3B A matching slice from the 3D gradient echo SHMC image is shown in FIG. 3B. Only sample areas next to the SHMC contributed to the detected MR signal.
  • a 3D reconstruction of fused gradient echo images obtained using a standard RF coil and the SHMC excitation are shown in FIG. 3A.
  • FIG. 4A illustrates a side view of an RF coil attached to a subject.
  • FIGS. 4B-4C illustrate images related to an in vivo second harmonic excitation MR experiment, according to an embodiment of the present invention.
  • In vivo MR experiments were performed after implanting SHMC in the mouse back and positioning animal in a 30 mm RF resonator, with the transmit RF coil attached to the animal, illustrated in FIG. 4A.
  • Coronal and axial fused images obtained with a standard FLASH (gray-scale) and SHMC generated harmonics are shown in FIGS. 4 B and 4C. Coronal images were generated by maximum intensity projections of 6-8 slices extracted from 3D data matrices for the FLASH and SHMC imaging, respectively.
  • the present invention includes a novel technique to excite MR signals using a second harmonic generated by an RF coil with a nonlinear diode element driven at a half resonance frequency of the spectrometer.
  • the method can be used to detect spatially localized spectra and images generated by spins in close proximity to the coil.
  • One of the potential applications of the method includes using the coil for MR traceable probes to precisely measure the probe position and to overlay the probe location with a standard anatomical MR image during interventional procedures.

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Engineering & Computer Science (AREA)
  • Medical Informatics (AREA)
  • Biophysics (AREA)
  • Pathology (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Biomedical Technology (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Radiology & Medical Imaging (AREA)
  • Molecular Biology (AREA)
  • Surgery (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)

Abstract

La présente invention concerne un système et un procédé d'excitation harmonique de signal de résonance magnétique (RM) aux fins d'imagerie par résonance magnétique (IRM) interventionnelle. Le système comprend une bobine RF implantable qui excite des signaux RM chez le sujet, lorsqu'elle est attaquée par un champ RF de plus basse fréquence en provenance d'une bobine externe. Cette approche permet la détection de signal RM à proximité immédiate de la bobine insérée par une bobine réceptrice IRM standard sans le contexte du reste du sujet. L'acte permet une détermination précise d'une position de la bobine insérée, à l'intérieur du sujet. L'acte permet également d'obtenir des images et des spectres RM localisés.
PCT/US2015/033652 2014-06-02 2015-06-02 Excitation harmonique de signal rm pour irm interventionnelle WO2015187607A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201462006296P 2014-06-02 2014-06-02
US62/006,296 2014-06-02

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5699801A (en) * 1995-06-01 1997-12-23 The Johns Hopkins University Method of internal magnetic resonance imaging and spectroscopic analysis and associated apparatus
US20030171787A1 (en) * 2000-06-30 2003-09-11 David Money Cochlear implant
US20040068298A1 (en) * 2000-03-17 2004-04-08 Jordi Parramon Voltage converter for implantable microstimulator using RF-powering coil
US20100256481A1 (en) * 2007-09-27 2010-10-07 Mareci Thomas H Method and Apparatus for Providing a Wireless Multiple-Frequency MR Coil
US20120223705A1 (en) * 2007-12-21 2012-09-06 T2 Biosystems, Inc. Magnetic resonance system with implantable components and methods of use thereof

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5699801A (en) * 1995-06-01 1997-12-23 The Johns Hopkins University Method of internal magnetic resonance imaging and spectroscopic analysis and associated apparatus
US20040068298A1 (en) * 2000-03-17 2004-04-08 Jordi Parramon Voltage converter for implantable microstimulator using RF-powering coil
US20030171787A1 (en) * 2000-06-30 2003-09-11 David Money Cochlear implant
US20100256481A1 (en) * 2007-09-27 2010-10-07 Mareci Thomas H Method and Apparatus for Providing a Wireless Multiple-Frequency MR Coil
US20120223705A1 (en) * 2007-12-21 2012-09-06 T2 Biosystems, Inc. Magnetic resonance system with implantable components and methods of use thereof

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