Abstract: An RF coil assembly for an NMR instrument includes a cylindrical shield disposed concentrically about a central axis and a set of linear conductors disposed concentrically about the central axis and radially inward from the shield. Assembly further includes an annular member positioned to span the gap between the shield and linear conductors. The annular member includes an insulating substrate, a conductive layer over the substrate, and a series of non-conducting gaps through the conductive layer. One or more lumped element capacitors are connected across one or more of the gaps to tune to resonance.

Abstract: RF coil apparatus is provided for use in an MR imaging system, wherein the B.sub.0 field is oriented in a specified direction. The apparatus comprises a coil structure positioned in selected relationship with the B.sub.0 field, the coil structure comprising a pair of elongated coil members in spaced-apart parallel relationship, and a selected number of lateral coil members positioned along the elongated coil members in spaced-apart parallel relationship with one another. A number of first capacitive elements, each of a first capacitance, are selectively positioned along the elongated coil members, and a second capacitive element is included in each of the lateral coil members, each of the second capacitive elements being of a second capacitance. A first coupling network operates the coil structure to selectively transmit and receive a first RF field component directed along a first axis which is orthogonal to the B.sub.

Abstract: A whole body RF coil provided for use with an open MR magnet system comprises first and second RF coil components selectively spaced apart from each other on opposite sides of an imaging space disposed to receive a subject, each of the RF coil components comprising a plurality of electrically conductive inner and outer arc segments which respectively lie on corresponding inner and outer circular paths. The RF coil is constructed to allow the subject to pass through the inner and outer circular paths of a selected one of the coil components or alternatively between the spaced apart RF coil components, into imaging space. The first and second RF coils are each energized in quadrature to generate respective corresponding first and second magnetic fields which collectively provide a resultant field comprising the B.sub.1 field component required for imaging.

Abstract: An angiographic coil for performing blood flow studies of the large vessels of the legs and lower pelvis employs an alternating series of coil elements having orthogonal sensitivities arrayed along a cover and base surrounding the legs and lower pelvis and supported thereby. The alternating coil pattern provides good isolation between the coils in a coil that allows easy patient positioning. In a second embodiment, structures having conductors pass between the legs when the patient's legs straddle a divider of the coil form. The coil structure is open on sides to permit easy entrance and exit from the coil by the patient. Multiple coils are used to span the length of the elongate imaging area of the legs and a pre-amplifier network is employed to limit the inductance between other coil and to provide for piecewise imaging of the entire leg and pelvis region.

Abstract: A quadrature local coil includes two coil sets placed on opposite sides of the patient, each coil set having a single loop and a split loop so as to be sensitive to quadrature components of a flux field substantially centered between the coil sets. Signals are developed from the loops in a manner to reduce current flow in the loops preventing coupling of the opposing loops and the degradation of the signal. The signals may be summed to produce a single signal of improved signal-to-noise ratio.

Abstract: A local coil for magnetic resonance imaging of the breast employs two generally cylindrical coils isolated from each other by a radio frequency shield. The coils comprise multiple loops displaced along the axis of the cylinder and connected in parallel to provide uniform coverage of the volume. Coils may be activated individually or at the same time with their signals combined. In the former case, the non-activated coil is actively decoupled by stimulating its decoupling circuit network with a DC bias signal from the system. The activated coil decouples passively during transmit.

Abstract: A quadrature local coil includes a bifurcated first loop positioned on one side of the patient and sensitive to RF magnetic flux generally parallel to the surface of the loop and a second loop positioned on the other side of the patient, opposed to the first loop and sensitive to RF magnetic flux within the patient perpendicular to that to which the first loop is sensitive. In one embodiment, the first and second loops are mounted in opposing concave shells held against and supported by the patient.

Abstract: A quadrature coil for receiving NMR signals in magnetic resonance imaging employs as few as two substantially coplanar overlapping loops having sensitivity along perpendicular lines in a region of sensitivity. Each loop is sensitive to a fluctuating uniform magnetic field but is decoupled by a decoupling network. A common ground point shared between the two loops allows the combination of the signals produced by the two loops with a hybrid combiner without the coupling of the loops through the signal's grounds. A third loop may be added to the two loops to produce a third signal to further improve the signal-to-noise ratio of the coil.

Abstract: A magnetic resonance imaging detection coil includes an outer coil divided into two symmetrical coils by a transverse central conductor. A 180.degree. phase shift network is coupled across the junction of the central transverse conductor with the outer conductor for providing the central conductor with a virtual ground potential when a magnetic field normal to the general plane of the coil system is present. The two coils formed by the central conductor and the outer conductor form parallel coils functioning similarly as a butterfly coil. The currents in the central conductor are cumulative, flowing in the same direction. The parallel coil system induces current on the central conductor which is 90.degree. out of phase with the current induced in the outer conductor. The signals corresponding to the parallel coil and series coil arrangement are then phase shift combined to place these signals in phase.

Abstract: For measurements with increased accuracy in a nuclear magnetic resonance apparatus, the detection device is equipped with one or more surface coils which act as measuring coils. To avoid mutual interference between a radio-frequency transmitting coil and the measuring coil, the measuring coil is provided with a decoupling circuit. The surface coil and the decoupling circuit form a part of a tuned circuit which is tuned to a significantly higher natural frequency during activation of the transmitting coil. On the other hand, the transmitting coil is shorted during detection with the surface coil by a low resistance shorting circuit, thereby avoiding interference with the radio-frequency transmission signals.

Abstract: An Rf coil system for the detection of MR resonance signals is constructed from a first system of coils for making an overall picture and a second coil system which covers substantially the same area, consists of several coils and for local imaging having a higher resolving power. In particular the latter coils preferably include magnetic resonance sensitive material which become visible on an image formed from detected MR resonance signals for indicating the position of each coil.

Abstract: In a magnetic resonance apparatus with an rf detection coil system constructed from overlapping coils the extent of overlap has been chosen to be so that the mutual inductance between overlapping coils is restricted to a non-disturbing minimum by flux compensation. As a result of this the coils of the cascade can be operated simultaneously for the measurement of coronal and sagittal slices without detrimental mutual influence.

Abstract: A magnetic resonance imaging apparatus includes a cascade of surface coils for detection so that larger objects can be measured while the attractive signal-to-noise ratio of surface coils is retained without mutual re-orientation of coils with respect to the object being required. By introducing a partial overlap between successive coils, suitable homogeneity can be achieved for the detection.

Abstract: A surface coil used as a measuring coil in a magnetic resonance apparatus is divided into at least two coil portions having opposite directions of winding and enclosing two identical surface areas. An induction current generated in a coil portion by a transmission field is then always compensated for by a current generated in the other coil portion. When one or more of such butterfly coils are used no circuits to block interfering signals need be built into the electronic measuring circuit and the transmission field is not disturbed by the measuring coil.

Abstract: The detection coil of a magnetic resonance imaging apparatus comprises a stack of two coils with locally mutually perpendicularly directed B Fields. The first coil is formed as a butterfly coil having a B field extending parallel to the plane of the coil, the second coil being formed by a single flat coil having a B field extending transversely of the plane of the coil. The coils are arranged in a fixed mutual orientation so that for each of the coils reciprocally applied fluxes are always compensated for.