WO2006010955A1 - Detection nmr dans le champ de franges non homogenes d'un aimant - Google Patents

Detection nmr dans le champ de franges non homogenes d'un aimant Download PDF

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Publication number
WO2006010955A1
WO2006010955A1 PCT/GB2005/003009 GB2005003009W WO2006010955A1 WO 2006010955 A1 WO2006010955 A1 WO 2006010955A1 GB 2005003009 W GB2005003009 W GB 2005003009W WO 2006010955 A1 WO2006010955 A1 WO 2006010955A1
Authority
WO
WIPO (PCT)
Prior art keywords
magnetic field
field
magnet
lineal region
response signals
Prior art date
Application number
PCT/GB2005/003009
Other languages
English (en)
Inventor
Jennifer Susan Gregory
Richard Malcolm Aspden
Hugh Charles Seton
Sanaa Faisal Rahmatallah
Yan Li
Original Assignee
Aberdeen 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 Aberdeen University filed Critical Aberdeen University
Publication of WO2006010955A1 publication Critical patent/WO2006010955A1/fr
Priority to GB0703965A priority Critical patent/GB2431727B/en

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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
    • G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
    • G01R33/3808—Magnet assemblies for single-sided MR wherein the magnet assembly is located on one side of a subject only; Magnet assemblies for inside-out MR, e.g. for MR in a borehole or in a blood vessel, or magnet assemblies for fringe-field MR
    • 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
    • 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

Definitions

  • This invention relates to magnetic resonance detection utilizing magnetic resonance ( ⁇ MR") methods.
  • ⁇ MR magnetic resonance
  • CT computed tomography
  • a high strength and highly homogeneous magnetic field (designated HO) is established in an examination zone, and a patient under examination is positioned so as to align an area of interest in the patient's body with the examination zone.
  • a cylindrical magnet configuration (of circular cross section) is employed, with the examination zone existing within the cylinder; the diameter of the cylinder being sufficient to accommodate a patient.
  • Means are provided to move the patient along the axis of the cylinder in order to effect the desired coincidence of the area of interest with the examination zone.
  • the response signals for processing are obtained by means of transceiver coils which both apply to and receive from the examination zone radio frequency electromagnetic fields (designated Hl) in a direction orthogonal to HO.
  • Hl radio frequency electromagnetic fields
  • the relationship between HO and Hl is controlled to select planar regions, within the body under examination, for which data are derived and processed to generate images of cross-sectional "slices" or laminae through the body; such images exhibiting a high degree of definition in both dimensions across the slice o'r lamina.
  • a drawback to the more general application of MR systems is their substantial cost, since the requirements for images of high resolution dictates the use of dimensionally large and highly homogeneous magnetic fields (designated HO) at high magnetic field strengths, leading to 5 the need for massive, powerful magnets and associated cryogenic systems.
  • HO dimensionally large and highly homogeneous magnetic fields
  • the magnets used in such applications have comprised U-shaped magnets.
  • solid bar magnets have been used to generate a magnetic field (HO) exhibiting a strong decay gradient (along the axis of the magnet) within an examination zone external 0 of the magnet.
  • HO magnetic field
  • RF radio frequency
  • An object of the present invention is to utilise MR principles in a method which is relatively inexpensive to implement and uses an external magnetic field to derive useful information from a plurality of locations at a range of different depths within a body or object under examination or test.
  • MR magnetic resonance
  • the gradient of the HO magnetic field over said lineal region is between 1 and 6 Tesla/metre, and at most 8 Tesla/metre.
  • said lineal region extends over at least 2mm.
  • said static field is generated by means of a permanent magnet and the lineal region is located a predetermined distance beyond a physical extremity of said magnet.
  • the Hl field is generated by a coil arrangement disposed closely adjacent said extremity.
  • the said lineal region is located at a point of inflexion in the axial magnetic field.
  • a preferred coil arrangement comprises an electromagnetic coil arrangement configured in "figure-8" form and comprising first and second semi-elliptical multi-turn loops, disposed with their flat faces adjacent and connected in parallel.
  • the invention also encompasses such methods as aforesaid together with the further 1 steps of detecting the response signals and correlating and processing said response signals to provide information about a distribution of resonance data in the body or object along the direction of, or substantially parallel to, said lineal region.
  • Figures l(a) and 1 (b) show, in cross-sectional and plan views respectively, a hollow, circular cross section cylindrical magnet for generating an HO field for use in a method in accordance with one embodiment of the invention
  • Figure 2 shows the HO field variation against axial position for the magnet of figure 1;
  • Figure 3 shows, in simplified plan view, a representation of a coil arrangement utilised in one example of the invention to generate the Hl field;
  • Figures 4 (a) and 4 (b) show, in cross-sectional and plan views respectively, a hollow, conical magnet for generating the HO field for use in a method according to another embodiment of the invention;
  • Figure 5 shows the HO field variation against axial position for the magnet of figure 4;
  • Figure 6 shows certain basic components of a detection apparatus capable of utilising the methods of the invention.
  • a tubular magnet 10 in the form of a right cylinder, having a hollow bore and a height h.
  • the magnet has an outer radius R 0 and an inner radius R 1 with an axis 12.
  • the magnet 10 is magnetised radially (i.e. in a direction substantially transverse to the axis 12) with N along the axially facing surface.
  • R 1 has a value of 28 mm
  • R 0 has a value of 50 mm
  • h has a value of 80 mm.
  • FIG 2 there is shown the magnetic field magnitude in milli Tesla taken along the axis 12 in mm. It can be seen that the peak field strength is external to the magnet, that is to say, it is beyond the end face or extremity of the magnet. Moreover, the decay of the field strength from the peak is relatively gradual or shallow compared with that normally associated with a solid bar magnet. The region just beyond the peak comprises the region of interest (ROI) 18 where a body to be examined is located. In practice, gradients of only 8 Tesla/metre or less; and preferably less than 6 Tesla/metre, are used.
  • a magnetic device in the form of a radio frequency (RF) coil arrangement of any convenient design is used to generate the Hl field, in a direction transverse to the axis 12.
  • RF radio frequency
  • a "figure-of-eight" coil 16 is used to generate the Hl field and excite the spins as well as to collect the response signals.
  • the coil arrangement 16 comprises two twelve-turn, semi-elliptical loops wound separately, disposed face-to-face and connected in parallel to form the "figure-of-eight". The coils are fed with equal currents of opposing polarity.
  • the coils of the arrangement 16 are wound of wire of diameter 0.5 mm, have an inductance of 1.2 microHenry and a Q-factor of 79.
  • the radio frequency is directly proportional to the magnetic flux density HOo and is selected according to the following formula:-
  • Figure 6 shows an example of a detection apparatus including the magnet of figure 1 and the coil of figure 3.
  • the coil 16 is deposited on the underside of a glass sheet 42 which is suspended in any convenient manner adjacent an end surface 44 of the magnet 10.
  • a first sample 46 for example rubber, is placed on top of the glass sheet 42.
  • a further sheet of glass 48 covers the sample 46 to act as a spacer and support for a second sample 50 of rubber. Glass sheets are used for support and separation as they do not give rise to the generation of potentially confusing response signals.
  • a circuit arrangement 52 of known kind is connected to the coil arrangement 16 to energise it to generate the Hl field and for receiving response signals.
  • the received response signals are fed to a processor 54 of known kind, configured to process the response signals and to produce output signals indicative of the samples 46 and 50.
  • the output signals so produced are applied to a monitoring and/or recording unit 56 of any convenient kind.
  • the method of the invention may be thus be configured in a so-called "1-D" mode to utilise the naturally shallow field gradient derivable, for example, from a hollow, tubular and radially magnetised magnet to provide comparative response signals at different depths of the body to be examined (i.e. along the line of axis 12, or parallel thereto) to effect spatial resolution within the region 14 (i.e. between locations separated along the line of axis 12) .
  • This is effected without the need to re-tune the RF coil for each different measuring location along the line from which response signals are to be derived.
  • the lineal extent of the region 14 is at least 2mm.
  • the magnet 10 it will be appreciated /that regions of defined field strength and gradients can be created by selection of the material of which the magnet is constructed and the geometry of the magnet, typical parameters to be selected including the height, inner diameter and outer diameter.
  • a typical material used for magnet construction in examples of the invention is neodymium iron boron (NdFeB) .
  • the direction of magnetisation in this example was such as to configure the outer surface of the magnet as South and the inner surface as North, though the polarisation can be reversed.
  • the magnet 10 may alternatively be magnetised axially (i.e. in a direction parallel with the axis 12) and in either direction.
  • Figures 4 (a) and 4 (b) show an example of an alternative magnetic element, in which a truncated conical magnet 20 is employed to generate a magnetic field distribution of the kind illustrated schematically in figure 0 5.
  • the maximum value 24 of the magnetic field HO also known as BO
  • BO magnetic field measured along the axis 22 (Z-axis) in milli Tesla
  • its position along the axis 22 from the end of the magnet 20 in mm, and the field gradients can be varied by altering the dimensions of the magnet 20; i.e. the height (h) measured 5 along the axis 22, upper inner radius r, upper thickness w, base angles ⁇ and ⁇ and the angle of the magnetisation direction ⁇ .
  • the conical magnet may be magnetised at any uniform angle with respect to its base plane, from 0 degrees (radial) through 90 degrees (axial) and 180 degrees (anti-radial) to 360 degrees, (anti-axial).
  • the central bore of the magnet may be wholly or partially filled with a material chosen to influence a particular characteristic of the HO field and to extend the range of distances over which the decay gradient of the HO field is sufficiently shallow to achieve the objective of achieving depth resolution without the need for re-tuning the Hl field.

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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Vascular Medicine (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)

Abstract

L'invention concerne un procédé pour faire fonctionner un système de résonance magnétique (MR) permettant de dériver des signaux de réponse pouvant être résolus à partir d'une pluralité d'emplacements répartis le long d'une région sensiblement linéaire d'examen ou de test par rapport à un corps ou un objet. Le procédé comprend les étapes suivantes : (a) production d'un champ magnétique de radiofréquence (H1) dans un sens sensiblement transversal par rapport à la région linéaire ; et (b) utilisation d'une source magnétique (10) pour produire, à l'extérieur de la source, un champ magnétique non homogène et statique ; le champ magnétique statique étant (i) dirigé de manière sensiblement parallèle à la région linéaire et s'étendant le long de celle-ci, tout en étant orthogonal par rapport au champ (H1) ; et (ii) la diminution de l'amplitude dudit champ magnétique statique est sélectionnée, de manière à ce qu'il soit peu profond par rapport au gradient, les signaux de réponse, pouvant être résolus, étant dérivés de la pluralité des emplacements, sensiblement sans réglage du champ magnétique de radiofréquences.
PCT/GB2005/003009 2004-07-30 2005-08-01 Detection nmr dans le champ de franges non homogenes d'un aimant WO2006010955A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB0703965A GB2431727B (en) 2004-07-30 2007-02-28 NMR detection in the inhomogeneous fringe field of a magnet

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0417094.0 2004-07-30
GBGB0417094.0A GB0417094D0 (en) 2004-07-30 2004-07-30 Magnetic resonance detection

Publications (1)

Publication Number Publication Date
WO2006010955A1 true WO2006010955A1 (fr) 2006-02-02

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PCT/GB2005/003009 WO2006010955A1 (fr) 2004-07-30 2005-08-01 Detection nmr dans le champ de franges non homogenes d'un aimant

Country Status (2)

Country Link
GB (2) GB0417094D0 (fr)
WO (1) WO2006010955A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008059474A1 (fr) * 2006-11-15 2008-05-22 Doron Kwiat Ensemble d'aimant réalisé à partir d'un matériau ferromagnétique ou d'une terre rare
GB2445759A (en) * 2006-11-28 2008-07-23 Inst Of Food Res Magnetic resonance imaging scanner
WO2009027973A1 (fr) * 2007-08-30 2009-03-05 Technion Research & Development Foundation Ltd. Spectroscopie rmn ex-situ

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6298602A (ja) * 1985-10-25 1987-05-08 Hitachi Ltd 円筒形永久磁石装置
US4717876A (en) * 1986-08-13 1988-01-05 Numar NMR magnet system for well logging
EP0399789A2 (fr) * 1989-05-22 1990-11-28 The Regents Of The University Of California Structure de champ marginal pour l'imagerie à résonance magnétique
US5757186A (en) * 1996-02-23 1998-05-26 Western Atlas International, Inc. Nuclear magnetic resonance well logging apparatus and method adapted for measurement-while-drilling
US6489872B1 (en) * 1999-05-06 2002-12-03 New Mexico Resonance Unilateral magnet having a remote uniform field region for nuclear magnetic resonance
US20030052679A1 (en) * 1998-04-17 2003-03-20 Morris Peter Gordon Magnetic gradient field projection
WO2003087861A1 (fr) * 2002-04-14 2003-10-23 Bluemich Bernhard Sonde d'imagerie par resonance magnetique concue pour des analyses de materiau
WO2004008168A1 (fr) * 2002-07-11 2004-01-22 Victoria Link Limited Appareil de resonance magnetique nucleaire

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6298602A (ja) * 1985-10-25 1987-05-08 Hitachi Ltd 円筒形永久磁石装置
US4717876A (en) * 1986-08-13 1988-01-05 Numar NMR magnet system for well logging
EP0399789A2 (fr) * 1989-05-22 1990-11-28 The Regents Of The University Of California Structure de champ marginal pour l'imagerie à résonance magnétique
US5757186A (en) * 1996-02-23 1998-05-26 Western Atlas International, Inc. Nuclear magnetic resonance well logging apparatus and method adapted for measurement-while-drilling
US20030052679A1 (en) * 1998-04-17 2003-03-20 Morris Peter Gordon Magnetic gradient field projection
US6489872B1 (en) * 1999-05-06 2002-12-03 New Mexico Resonance Unilateral magnet having a remote uniform field region for nuclear magnetic resonance
WO2003087861A1 (fr) * 2002-04-14 2003-10-23 Bluemich Bernhard Sonde d'imagerie par resonance magnetique concue pour des analyses de materiau
WO2004008168A1 (fr) * 2002-07-11 2004-01-22 Victoria Link Limited Appareil de resonance magnetique nucleaire

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
CASANOVA F ET AL: "Two-dimensional imaging with a single-sided NMR probe", JOURNAL OF MAGNETIC RESONANCE, ACADEMIC PRESS, ORLANDO, FL, US, vol. 163, no. 1, July 2003 (2003-07-01), pages 38 - 45, XP004435382, ISSN: 1090-7807 *
PATENT ABSTRACTS OF JAPAN vol. 011, no. 306 (E - 546) 6 October 1987 (1987-10-06) *
RAHMATALLAH S ET AL: "NMR detection and one-dimensional imaging using the inhomogeneous magnetic field of a portable single-sided magnet", JOURNAL OF MAGNETIC RESONANCE, ACADEMIC PRESS, ORLANDO, FL, US, vol. 173, no. 1, March 2005 (2005-03-01), pages 23 - 28, XP004738990, ISSN: 1090-7807 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008059474A1 (fr) * 2006-11-15 2008-05-22 Doron Kwiat Ensemble d'aimant réalisé à partir d'un matériau ferromagnétique ou d'une terre rare
GB2445759A (en) * 2006-11-28 2008-07-23 Inst Of Food Res Magnetic resonance imaging scanner
WO2009027973A1 (fr) * 2007-08-30 2009-03-05 Technion Research & Development Foundation Ltd. Spectroscopie rmn ex-situ
US8461836B2 (en) 2007-08-30 2013-06-11 Technion Research & Development Foundation Limited Method and device for ex situ magnetic resonance analysis

Also Published As

Publication number Publication date
GB0417094D0 (en) 2004-09-01
GB0703965D0 (en) 2007-04-11
GB2431727B (en) 2008-10-22
GB2431727A (en) 2007-05-02

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