Method and apparatus for minimizing gradient coil and rf coil coupling
AssigneeGE Medical Systems Global Technology Company, LLC
InventorEddy B. Boskamp
Life of this patent
Estimating the term…
Abstract
A method and apparatus are provided which reduce coupling between a Z-axis gradient coil and an rf coil in magnetic resonance imaging systems and an rf shield disposed between the Z-axis gradient coil and the remaining gradient coils. The reduction in coupling is accomplished by novel windings of conductor forming the Z-axis gradient coil.
Claims43
A magnetic resonance imaging system comprising:
- a radiofrequency (rf) coil comprising two end rings connected by a plurality of rungs disposed perpendicular to the plane of the end rings;
- and
- a gradient coil, disposed about the rf coil, comprising a gradient conductor wound as a solenoid coil in which there is a gap above each end ring which is crossed by a portion of the conductor.
A magnetic resonance imaging system comprising:
- a radiofrequency (rf) coil comprising two end rings connected by a plurality of rungs disposed perpendicular to the plane of the end rings;
- and
- a gradient coil, disposed about the rf coil, comprising a gradient conductor wound as a solenoid coil which is symmetric about an isocenter of a field formed by the gradient coil such that the gradient coil comprises a positive half and a negative half which are connected by a segment of the gradient conductor forming a symmetric spirally wound connecting wire.
A magnetic resonance imaging system comprising:
- a birdcage radiofrequency (rf) coil generally forming an inner tube comprising a pair of end rings connected by a plurality of spaced apart rungs disposed perpendicular to the plane of the end rings;
- and
- a gradient coil generally forming an outer tube disposed about the inner tube comprising a conductive element wound to form a solenoid coil such that there is a gap in the solenoid coil above each end ring of the rf coil and such that the winding of the solenoid coil is reversed at a transverse plane bisecting the coil wherein a minimum amount of conductive element is used to cross each gap and wherein the conductive element crossing the transverse plane comprises a symmetric spirally wound segment which circles the inner tube in multiples of one half of a turn prior to reversing.
A gradient coil for use with a whole body rf coil of a MR imaging system, the gradient coil comprising a conductor wound as a solenoid coil in which the winding is reversed at a transverse plane located at the isocenter of a field generated by the gradient coil, forming a first winding and a reversed, second winding, the transition from the first winding to the second winding being accomplished by a spirally wound segment of the conductor which passes around the whole body rf coil at least one half of a turn prior to reversing.
A coil for use with a whole body rf coil of a MR imaging system, the coil comprising a conductor wound as a solenoid coil in which the winding is reversed at a transverse plane located at the isocenter of a field generated by the coil to form a first winding and a reversed, second winding, and further comprising a pair of gaps, one on either side of the transverse plane, wherein each gap is situated so that the solenoid coil is not wound above a pair of end rings of the whole body rf coil and wherein a minimum amount of conductive material crosses each gap.
A method of winding a gradient coil to reduce coupling between the gradient coil and a radiofrequency (rf) coil comprising the act of:
- winding a conductor about the rf coil to form a solenoid coil;
- forming a spiral of the conductor, as the location of a desired isocenter for a gradient field produced by the gradient coil is approached, such that the spiral passes around the rf coil in increments of half of a turn prior to reversing;
- and
- reversing the winding of the solenoid coil at the location of the desired isocenter to form a symmetric solenoid coil about the desired isocenter such that a reversed spiral is formed as part of the symmetric solenoid coil.
A method of winding a gradient coil to reduce coupling between the gradient coil and a radiofrequency (rf) coil comprising the act of:
- winding a conductor about the rf coil to form a solenoid coil;
- forming a gap in a portion of the solenoid coil disposed above an end ring of the rf coil such that the gap is crossed by a length of the conductor;
- and
- reversing the winding of the solenoid coil at the location of a desired isocenter for a gradient field produced by the gradient coil to form a symmetric solenoid coil about the desired isocenter.
A magnetic resonance imaging system comprising:
- a radiofrequency (rf) coil comprising two end rings connected by a plurality of rungs disposed perpendicular to the plane of the end rings;
- a gradient coil, disposed about the rf coil, comprising a gradient conductor generally wound as a symmetric solenoid coil in which the winding of the solenoid is reversed at the at a location corresponding to an intersection with a transverse plane passing through the desired isocenter of a gradient field produced by the gradient coil;
- and
- a means for decoupling a portion of the gradient coil from an underlying end ring.
A magnetic resonance imaging system comprising:
- a radiofrequency (rf) coil comprising two end rings connected by a plurality of rungs disposed perpendicular to the plane of the end rings;
- a gradient coil, disposed about the rf coil, comprising a gradient conductor generally wound as a symmetric solenoid coil in which the winding of the solenoid is reversed at the at a location corresponding to an intersection with a transverse plane passing through the desired isocenter of a gradient field produced by the gradient coil;
- and
- a means for distributing among the rungs any coupling between a segment of the gradient conductor and the rf coil such that the coupling is distributed substantially equally among the rungs.
Dependencies are inferred from the claim text.