Hybrid resonator

• US 4,757,290 A
• Filed: 02/06/1987
• Issued: 07/12/1988
• Est. Priority Date: 02/20/1986
• Status: Expired due to Fees

• Current Assignee: GE Medical Systems Israel, Ltd
• Original Assignee: Elscint Limited (Elbit Imaging Limited)
• Inventors: Keren, Hannan
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/011,630
• Time in Patent Office: 522 Days
• Field of Search: 333/167, 333/219, 333/235, 333/245, 333/220-223, 333/227, 333/231, 324/311, 324/316, 324/318, 324/320, 324/321, 324/322, 324/307, 324/308, 324/309, 324/310, 324/312, 324/313, 335/299, 335/301
• US Class Current: 333/219
• CPC Class Codes: G01R 33/34046 Volume type coils, e.g. bird-cage coils; Quadrature bird-cage coils; Circularly polarised coils
• CPC Class Codes: G01R 33/3678 involving quadrature drive or detection, e.g. a circularly polarized RF magnetic field

Abstract

A circularly polarized radio frequency probe for use in magnetic resonance systems, the probe comprises four effective "saddle coils" arranged to define a single cylinder. The saddle coils each comprise a pair of 120 degree arcuate conductor sectors separated by longitudinal conductors. RF power is coupled to each of said "saddle coils" so that first and second pairs of said saddle coils generate first and second fields normal to each other.

Claims

1. A hybrid resonator for use as a radio frequency probe in magnetic resonance (MR) systems,

said systems having large static magnetic field extending in a longitudinal direction in a cylinder,

said resonator comprising a pair of oppositely disposed spaced apart circular end coils,

said end coils each being concentric about the same axis to thereby define a cylindrical shape,

four longitudinal coils disposed between said circular end coils symetrically spaced apart around said cylindrical shape,

each of said longitudinal coils comprising a pair of spaced apart longitudinal conductors,

a pair of transverse conductors joining the longitudinal conductors at opposite ends thereof,

said transverse conductors being adjacent and parallel to portions of said circular end coils,

means for connecting each of said longitudinal coils to both of said circular end coils,

capacitor means for tuning the hybrid resonator to the desired resonance frequency, and

means for connecting radio frequency power to said hybrid resonator.

2. The hybrid resonator of claim 1 wherein said means for connecting each of said longitudinal coils to both of said circular end coils comprises means for connecting each of said transverse conductors at the midpoint thereof to said adjacent circular end coils.

3. The hybrid resonator of claim 2 wherein said capacitor means is located in the means for connecting each of said transverse conductors to said adjacent circular end coil.

4. The hybrid resonator of claim 3 wherein said means for connecting radio frequency power to said hybrid resonator comprises means for coupling a first RF source to one pair of oppositely disposed longitudinal coils and means for connecting a second RF source to the other pair of oppositely disposed longitudinal coils, and

said first Rf source being 90 degrees out of phase with said second Rf source.

5. The hybrid resonator of claim 3 wherein said capacitor means comprises a matching capacitor in series with a tuning compacitor, and

wherein said means for connecting power comprises connecting said Rf sources across said matching capacitors.

6. The hybrid resonator of claim 3 wherein said capacitor means comprises a matching capacitor and a tuning capacitor in series with the matching capacitor where said RF sources are connected.

7. The hybrid resonator of claim 3 wherein said capacitor means comprises only a tuning capacitor unless said Rf is connected thereto, said tuning capacitor being the means for connecting said longitudinal coils to said circular end coils.

8. The hybrid resonator of claim 1 wherein said longitudinal coils each extend over an arc of 60 degrees and are separated from each other by an arc of 30 degrees.

9. The hybrid resonator of claim 1 wherein the points of connecting said longitudinal coils to said circular end coils are separated by 90 degrees.

10. The hybrid resonator of claim 1 wherein said Rf sources are connected so that the current in said circular end coils is opposite in direction than the current in the adjacent transverse conductors of said longitudinal coils.

11. The hybrid resonator of claim 1 wherein said RF power is connected so that current in adjacent ones of said longitudinal conductors of different ones of said longitudinal coils run in opposite directions.

12. A hybrid resonator for use as a radio frequency (RF) coil in a magnetic resonance (MR), said system having a large static magnet extending in a longitudinal direction in a cylinder, said resonator comprising a pair of oppositely disposed spaced apart circular end coils, said end coils being concentric about the same axis to thereby define a cylindrical shape, four longitudinal coils disposed between said circular end coils symmetrically spaced apart around said cylindrical shape and arranged to provide in cooperation with said circular end coils saddle coils symmetrically spaced around said cylindrical shape, said longitudinal coils extending for 60 degrees, said saddle coils being comprised of longitudinal members of oppositely disposed ones of said longitudinal coils being separated by an arc of 120 degrees, and each of said saddle coils being oppositely disposed from another saddle coil and spaced apart from each other by the 60 degree extension of said longitudinal coils.

13. The hybrid resonator of claim 14 including means for tuning said hybrid resonator to the desired RF, means for connecting RF power to said hybrid resonator in a manner to electromagnetically isolate each of said pair of saddle coils from the other pair of saddle coils whereby each pair of saddle coils can be tuned to a different RF for activating a different element in an object being subjected to magnetic resonance diagnosis in the MR system.