Shield for MR system RF coil provided with multiple capacitive channels for RF current flow
First Claim
1. In an MR imaging system having an RF coil and one or more gradient coils, apparatus for shielding the gradient coils from an RF field generated by the RF coil which rotates around the axis thereof, said apparatus comprising:
- an arrangement comprising a specified number of conductive cylinders in spaced-apart coaxial relationship;
a cylinder formed of selected dielectric material respectively positioned in each space lying between every two of said conductive cylinders which are adjacent to each other in said arrangement;
a pattern of conductive loops being formed in each of said conductive cylinders, each loop having an associated gap provided as a barrier to current flow; and
said specified number of said conductive cylinders, and their respective angular orientations relative to one another, are selected to provide a plurality of closed paths for RF current induced by the RF field, wherein respective closed paths are established by capacitive coupling between a given conductive loop of a given conductive cylinder, and conductive loops of each of a plurality of other of said conductive cylinders.
1 Assignment
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Accused Products
Abstract
An RF shield is provided to prevent coupling between the gradient coils and the RF coil of an MR imaging system, wherein the RF field rotates around the RF coil axis. The shield includes a number of coaxial conductive cylinders, and further includes a plurality of cylinders formed of dielectric material, each dielectric cylinder positioned between adjacent conductive cylinders. Each conductive cylinder is formed from sheets of copper, each sheet having a pattern of conductive loops formed therein, and each loop having an associated gap to prevent induction of eddy currents therein by gradient magnetic fields produced by the MR system gradient coils. The number of conductive cylinders, and the angular orientation thereof with respect to one another, are selected to provide a plurality of closed paths for RF image current induced by the RF field, wherein respective closed paths are established by capacitive coupling between a given conductive loop of a given conductive cylinder, and conductive loops in other of the conductive cylinders.
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Citations
11 Claims
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1. In an MR imaging system having an RF coil and one or more gradient coils, apparatus for shielding the gradient coils from an RF field generated by the RF coil which rotates around the axis thereof, said apparatus comprising:
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an arrangement comprising a specified number of conductive cylinders in spaced-apart coaxial relationship; a cylinder formed of selected dielectric material respectively positioned in each space lying between every two of said conductive cylinders which are adjacent to each other in said arrangement; a pattern of conductive loops being formed in each of said conductive cylinders, each loop having an associated gap provided as a barrier to current flow; and said specified number of said conductive cylinders, and their respective angular orientations relative to one another, are selected to provide a plurality of closed paths for RF current induced by the RF field, wherein respective closed paths are established by capacitive coupling between a given conductive loop of a given conductive cylinder, and conductive loops of each of a plurality of other of said conductive cylinders. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification