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WO1997033185A1 - Bobines paralleles a alimentation centrale pour imagerie rmn - Google Patents

Bobines paralleles a alimentation centrale pour imagerie rmn Download PDF

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Publication number
WO1997033185A1
WO1997033185A1 PCT/US1997/003429 US9703429W WO9733185A1 WO 1997033185 A1 WO1997033185 A1 WO 1997033185A1 US 9703429 W US9703429 W US 9703429W WO 9733185 A1 WO9733185 A1 WO 9733185A1
Authority
WO
WIPO (PCT)
Prior art keywords
coil
semi
coils
center
inductance
Prior art date
Application number
PCT/US1997/003429
Other languages
English (en)
Inventor
F. David Doty
George Entzminger, Jr.
Original Assignee
Doty F David
Entzminger George Jr
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 Doty F David, Entzminger George Jr filed Critical Doty F David
Priority to AU20677/97A priority Critical patent/AU2067797A/en
Priority to US09/101,737 priority patent/US6175237B1/en
Priority to CA002244847A priority patent/CA2244847C/fr
Publication of WO1997033185A1 publication Critical patent/WO1997033185A1/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
    • G01R33/34—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
    • G01R33/34069—Saddle coils

Definitions

  • the field of this invention is the measurement of nuclear magnetic resonance (NMR and MRI) for the purpose of determining molecular or microscopic structure, and, more particularly, an improvement in rf sample coils for double- resonance multinuclear applications.
  • NMR and MRI nuclear magnetic resonance
  • This invention pertains to improving the tunability of NMR and MRI coils, particularly in double-resonance multinuclear experiments on large samples at high fields, by means of novel paralleling and rf feed arrangement on saddle coils and the like for use on cylindrical surfaces aligned with B 0 .
  • Related NMR coils are described by Zens in U.S. Pat no. 4/398,149, Hill and Zens in U.S.' Pat no. 4,517,516, and Doty in U.S. Pat. no. 4,641,098, and again by Doty in a copending application.
  • the Zens US. pat. no. 4,398,149 illustrates the traditional methods of connecting spiral windings (referred to as semi- coils) on opposite sides of a cylinder in series. More recently, as magnet technology has progressed to higher fields, it has become common to connect 2-turn se icoils in parallel, thereby achieving the higher B ⁇ homogeneity that is possible with the conventional 4-turn saddle coil but at the lower inductance of the 2-turn saddle coil.
  • the NMR spectroscopist often finds it necessary to observe a wide variety of nuclides, especially. 13 C, 1 H, 1 F, 27 A1, 2 Si, 23 Na, 2 H, and 15 N in the study of commercially and scientifically important chemicals, and considerable interest is developing in multi-nuclear localized MR spectroscopy. Often it is important to simultaneously decouple dipolar effects of X H; and inverse experiments, in which the effects of decoupling a low-gamma nuclide are observed in the H spectra, have become extremely powerful and popular.
  • Multi-nuclear double-tuning is readily achieved in prior art designs with sample diameters up to 12 mm at fields up to 9.4 T with multi- turn saddle coils having inductance typically in the range of 30 to 70 nH. Multi-nuclear triple-resonance is available for 5-mm samples at fields up to 17.6 T (750 MHZ).
  • a copending application discloses coil geometries suitable for double- resonance multinuclear tuning for large samples at high fields with improved B y homogeneity.
  • the if voltages in this mode on ea Of each the leads is zero somewhere near the point where they are paralleled, the voltage at the remote end of one semi-coil is a maximum with phase ⁇ and the voltage at the remote end of the opposite semi-coil is a maximum with phase ⁇ + ⁇ .
  • the B ! from the differential twin-line mode is generally orthogonal to the z axis and to the LF B ⁇ axis.
  • twin-line modes of paralleled semi-coils are not known to cause problems in single-tuned multinuclear applications, as one is normally limited in these cases to operation at frequencies below the fundamental self-resonance of the complete coil, which is normally much lower than the lowest twin-line mode.
  • two orthogonal saddle coils are used in double-tuned multinuclear situations such as 1 H-X 1 the differential twin-line mode of the multi-X (low-gamma) coil could easily be very near the X H frequency.
  • the instant invention provides a simple method of approximately doubling the frequency of the differential twin- line mode of paralleled semi-coils. This nearly doubles the limiting frequency-diameter product for which efficient multinuclear double resonance is practical.
  • the two halves (semi-coils) of a conventional rf saddle coil, such as spirals or other related structures, for use in high resolution NMR or MRI, on opposite sides of a cylindrical coilform, are rotated from the conventional orientation 90° about the B : axis so that the leads from the two semi-coils meet and are paralleled near the axial center of the rf coil, thereby greatly increasing the differential twin-line mode of the resonant structure.
  • Figure 1 illustrates a center-feed method of paralleling two 2-turn semi-coils.
  • Figure 2 illustrates a center-feed method of paralleling two 1-turn semi-coils.
  • Figure 1 illustrates the center-feed method of essentially eliminating the differential twin-line mode in, for example, a typical two-turn paralleled saddle coil intended to be used as the low-frequency (LF) multinuclear coil in combination with a second orthogonal coil for the high frequency (HF) .
  • the two semi-coils 10, 20 in this case are substantially rectangular spirals that may be made by any of the conventional processes: (a) laser cutting of magnetically compensated metal foil laminate, (b) chemical etching of copper-clad dielectric laminate, (c) mechanical forming of aluminum-filled copper tubing, etc.
  • the two semi-coils of Figure 1 are symmetrically related and similar to those by Golay, Hoult, Hill, Zens, and others, with the notable difference that the leads 11, 12, 21, 22 are brought out and paralleled by arcs 13, 23 between the two semi-coils near the center rather than at one end.
  • the pattern is similar to a 90° rotation of a conventional semi- coil with respect to the B 2 axis.
  • the paralleling arcs 13, 23 generate a short-range field orthogonal to the major Bj field from the coil, but their effect on Bj homogeneity may easily be made negligible by a small internal floating shield patch under the arcs if necessary.
  • Paralleling permits more turns in each semicoil for the desired inductance, and hence much better B x homogeneity may be achieved.
  • the paralleling direction is such that the two fields add. That is, the parallel saddle coil inductance is greater than half of the inductance of the individual semi-coils.
  • the instant invention is specifically directed toward multi-nuclear double-tuned applications, in which a lower inductance orthogonal HF resonator is used in combination with a center-fed LF multi-nuclear saddle coil.
  • the LF rf center-feed is accomplished by a balanced, half-shielded transmission stripline 30 formed from copper-clad laminate with the ground side toward the sample, as RF magnetic field from this transmission line is negligible compared to the central Bj and the leads 31, 32 must have low inductance for minimal loss in filling factor.
  • the LF feed line into the center of the coil allows the LF feed line to be at any impedance at the HF with respect to ground and still have negligible effect on the typical orthogonal HF coil (for example, an Aldermian-Grant resonator, etc.), which is normally near zero Impedance with respect to ground near its center.
  • the arcs at the two axial ends 14, 15, 24, 25 of each semi- coil now float freely, and the leads 31, 32 do not form part of a large loop around substantial net flux emanating from an orthogonal HF coil — as opposed to the prior art where the paralleling leads subtend roughly a mean arc of 180° at the base of the coil.
  • this coil and center-feed arrangement lack the symmetry desired for best B 0 homogeneity — with the major perturbation coming from the center-feed stripline dielectric.
  • the preferred dielectric material is usually foamed PTFE (teflon) because of its low dielectric constant and low 2 H content (after a bakeout). Copper-clad PTFE foam may not be commercially available, but it may be approximated by separating two single-clad thin laminates by PTFF foam.
  • FIG. 1 illustrates a one-turn saddle coil with an unbalanced, truncated, center-feed line.
  • Many other semi-coil patterns are possible, and a number of numerically optimized patterns offering higher B X homogeneity are the subject of a copending application.
  • Inverse (low-gamma) decoupling techniques are becoming more popular than conventional proton decoupling techniques.
  • the center-fed LF saddle coil will usually be positioned on the outside with the HF resonator on the inside.
  • the high order (unshimable) magnetic disturbances from the outer coil are typically about an order of magnitude less than from the inner coil.
  • the center-fed coil is the inner coil
  • a paramagnetic metal such as aluminum or iridium
  • the semicoils too would need to be precisely compensated for minimum magnetism, according to the prior art.
  • the width of the center-feed line would have to be reduced to minimize degradation of B, homogeneity of the outer coil.

Landscapes

  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)
  • Coils Or Transformers For Communication (AREA)

Abstract

Les deux moitiés (10, 20) d'une bobine traditionnelle RF en sellette en spirale ou autre structure voisine utilisée en imagerie RMN ou en IRM à haute résolution, disposées de part et d'autre d'une bobine cylindrique, sont soumises à une rotation à partir de leur orientation conventionnelle, de 90° autour de l'axe B1 de manière à ce que les conducteurs (31, 32) soient parallèles à proximité du centre axial de la bobine RF.
PCT/US1997/003429 1996-03-05 1997-03-05 Bobines paralleles a alimentation centrale pour imagerie rmn WO1997033185A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
AU20677/97A AU2067797A (en) 1996-03-05 1997-03-05 Center-fed paralleled coils for mri
US09/101,737 US6175237B1 (en) 1997-03-05 1997-03-05 Center-fed paralleled coils for MRI
CA002244847A CA2244847C (fr) 1996-03-05 1997-03-05 Bobines paralleles a alimentation centrale pour imagerie rmn

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US1284996P 1996-03-05 1996-03-05
US60/012,849 1996-03-05

Publications (1)

Publication Number Publication Date
WO1997033185A1 true WO1997033185A1 (fr) 1997-09-12

Family

ID=21757023

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1997/003429 WO1997033185A1 (fr) 1996-03-05 1997-03-05 Bobines paralleles a alimentation centrale pour imagerie rmn

Country Status (3)

Country Link
AU (1) AU2067797A (fr)
CA (1) CA2244847C (fr)
WO (1) WO1997033185A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT407463B (de) * 1998-06-04 2001-03-26 Siemens Ag Oesterreich Spule zur stehenden montage auf schaltungsträgern

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5329233A (en) * 1992-12-10 1994-07-12 General Electric Company Cylindrical local coil for nuclear magnetic resonance imaging
US5517120A (en) * 1993-11-24 1996-05-14 Medrad, Inc. Quadrature coil for neurovascular imaging and spectroscopy of the human anatomy
US5602557A (en) * 1994-09-29 1997-02-11 Siemens Aktiengesellschaft Mammography antenna arrangement for NMR examinations of a female breast

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5329233A (en) * 1992-12-10 1994-07-12 General Electric Company Cylindrical local coil for nuclear magnetic resonance imaging
US5517120A (en) * 1993-11-24 1996-05-14 Medrad, Inc. Quadrature coil for neurovascular imaging and spectroscopy of the human anatomy
US5602557A (en) * 1994-09-29 1997-02-11 Siemens Aktiengesellschaft Mammography antenna arrangement for NMR examinations of a female breast

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT407463B (de) * 1998-06-04 2001-03-26 Siemens Ag Oesterreich Spule zur stehenden montage auf schaltungsträgern

Also Published As

Publication number Publication date
CA2244847C (fr) 2003-06-10
CA2244847A1 (fr) 1997-09-12
AU2067797A (en) 1997-09-22

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