B1 gradient coils

Details B1 gradient coils B1 gradient coils

2000-12-21

2002-04-09

Williams, Hezron (Department: 2862)

Electricity: measuring and testing

Particle precession resonance

Spectrometer components

C324S320000, C324S307000

Reexamination Certificate

active

06369570

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to high-resolution nuclear magnetic resonance (NMR) spectroscopy and imaging and in particular to so-called X-Y B1 gradient coils for producing two quickly switchable orthogonal magnetic field gradients in a plane which is perpendicular to the direction of a homogeneous static magnetic RF field.
It has been known to take advantage of a magnetic field with a gradient in NMR spectroscopy. U.S. Pat. No. 5,323,113 issued Jun. 21, 1994 to Cory et al, for example, disclosed an NMR probe for generating both a homogeneous RF field over a sample volume and a radial field comprising two orthogonal gradient fields in a plane transverse to the homogeneous field. The structure with two coils connected in parallel to a signal generator tends to give rise to interference problems. No commercially available coils of this kind exist within the knowledge of the inventors herein.
It has also been known to structure a radio-frequency coil like a birdcage in order to obtain a highly homogeneous magnetic field as described, for example, in U.S. Pat. No. 4,694,255 issued Sep. 15, 1987 to C. Hayes and “Experimental Design and Fabrication of Birdcage Resonators for Magnetic Resonance Imaging” (T. Vullo, et al., Magnetic Resonance in Medicine, 24, 243 (1992)). Birdcage coils are so called because of their general structure having a pair of loop-shaped conductive elements (the “rings”) separated in a longitudinal direction and a plurality of conductive segments (the “strips”) evenly spaced about the circumference of and interconnecting these two loop-shaped conductive elements. Capacitors are inserted either in the strips for a low-pass coil, or in the rings for a high-pass coil, as illustrated in
FIGS. 1A and 1B
, respectively.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a birdcage-like coil for generating an improved RF magnetic field gradient.
It is another object of this invention to provide a birdcage-like X-Y B1 gradient coil for generating two quickly switchable orthogonal magnetic field gradients, say, in the X-direction and the Y-direction.
It is still another object of this invention to provide an improved X-Y B1 gradient coil for generating both a homogeneous RF field over a sample volume and a radial field comprising two orthogonal gradient fields without giving rise to unwanted interference between the so-called transmitter and receiver coils.


REFERENCES:
patent: 4694555 (1987-09-01), Hayes
patent: 4757290 (1988-07-01), Keren
patent: 5323113 (1994-06-01), Cory et al.
patent: 5642048 (1997-06-01), Crozier et al.
patent: 5680046 (1997-10-01), Frederick et al.
patent: 5898306 (1999-04-01), Liu et al.
patent: 5990681 (1999-11-01), Richard et al.
patent: 6043658 (2000-03-01), Leussier
patent: 6133737 (2000-10-01), Greim
Article by Vullo, et al., entitled “Experimental Design and Fabrication of Birdcage Resonators for Magnetic Resonance Imaging”, published inMagnetic Resonance in Medicine, vol. 24, pp. 24-252 (1992).

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