Abstract: In an MR system employing a phased array surface coil, a method is provided for reducing artifacts in an MR image acquired from a region of an object lying within a specified field of view, wherein the field of view has a dimension extending between first and second boundary limits. The method includes the step of positioning the phased array surface coil, which comprises a linear array of coil elements, in selected spatial relationship with the object region. The method further comprises selecting a particular coil element for use in acquiring MR data only if the coil element lies at least partially in a range which extends along the phased array and has a length equal to the field of view dimension, the range lying between positions respectively corresponding to the first and second boundary limits.

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.

Abstract: An arrangement is provided for supporting the inner and outer gradient coils of one or more gradient coil sets, the coils of each gradient coil set providing one of the orthogonal gradient magnetic fields for an MR imaging system. The arrangement includes an inner cylindrical coil form disposed to supportably carry an inner gradient coil of a coil set, an outer cylindrical coil form in coaxial spaced-apart relationship with the inner coil form disposed to supportably carry an outer gradient coil of the coil set, and a stiffening cylinder positioned between the inner and outer coil forms to divide the space therebetween into first and second volumes. A thermally conductive adhesive material, such as an epoxy containing alumina particulate material, is inserted into the first and second volumes to bond both the inner and outer coil forms to the stiffening cylinder, in order to hold the inner and outer gradient coils respectively carried by the coil forms in rigid fixed relationship with respect to one another.

Abstract: An NMR imaging apparatus includes an excitation coil with a plurality of conductive elements extending between two spaced-apart end loops to form conventional "birdcage" coil. A shield is provided to reduce interference between the excitation coil and gradient field coils. The shield comprises a first electrically conductive section having an open ring with a gap therein and a plurality of first members extending from the ring with each member terminating at a remote end. A capacitor is connected across the gap in the ring. A second electrically conductive section has another ring from which a like plurality of second members extend with each one terminating at a remote end. The remote end of each second member is spaced from a remote end of a corresponding one of the first members and a capacitor is connected across those remote ends.

Abstract: An NMR excitation coil includes a plurality of conductive elements having varying lengths and arranged parallel to one another to define cylindrical volume. A planar loop connects one end of the conductive element together with the conductive segments between pairs of the conductive elements. A non-planar loop connects the other ends of the conductive elements with a series of conductive segments between pairs of the conductive elements. Some of the non-planar loop segments are formed by a coaxial cable having a central conductor connected between ends of two conductive elements and a shield the electrically floats. A separate capacitor is located in those segments of the two loops that are not formed by coaxial cables. Each capacitor has a capacitance which is defined by the inductance of the conductive elements connected to that capacitor.

Abstract: A high-pass bird cage coil serves as the whole-body RF coil in an NMR system. This coil is detuned when other RF coils are used to transmit or receive during a pulse sequence. This detuning is accomplished by detuning circuits that contain pin diodes which shunt the tuning capacitors in the bird cage coil.