Abstract: A primary gradient coil assembly (22) is mounted in the inner bore or cylinder (20) of a vacuum dewar (18) that surrounds a superconducting magnet assembly (10). A pair of end ring assemblies, such as electrically conductive lapped segment loops (38) are supported by the gradient coil assembly (22). The end ring segments are capacitively coupled. A plurality of removable radio frequency coil element assemblies (40) are selectively attached to and detached from the gradient coil assembly. Each of the removable RF coil element assembly includes a dielectric housing (50), a longitudinally extending conductor element (52), an electrical connector (44), and circuit components (54) which connects the longitudinal conductor element with the electrical connector. The connector is electrically connected, at radio frequencies, with the ring assembly (38). A mechanical interlock (60) mechanically locks and selectively releases the removable element assemblies (40) to the gradient coil assembly.

Abstract: A toroidal vacuum dewer (22) holds a superconducting magnet assembly (10) which generates a substantially temporally constant magnetic field through a central bore (12). A whole body gradient coil (30) and a whole body RF coil assembly (32) are mounted to a cylindrical member (24) of the dewar. An insertable gradient coil assembly (40) is selectively insertable into and removable from the bore. The insertable gradient coil assembly includes gradient coils for selectively generating magnetic field gradients along three mutually orthogonal axes, e.g. x, y, and z-axes. A flexible cable (42) connects the insertable gradient coil with a series of current amplifiers (44). The current amplifiers selectively generate current pulses which are fed along feed conductors (84) of the coil assembly and which return along return conductors (86) of the cable. The feed and return conductors are configured such that the net feed and the net return current traverse the same effective path in opposite directions.

Abstract: In a magnetic resonance system, four primary loop circuits (50, 52, 54, 56) are inductively coupled to a resonator coil (32) at 90.degree. intervals around its circumference. The loop circuits are over-coupled to the resonator coil, i.e. they present more than the characteristic resistance of the associated cabling system which causes the maximum current transfer between the loop circuits and the resonator coil to be offset (f.sub.N) in equal amounts in each direction from a natural resonance frequency (f.sub.0) of the resonator coil. In one embodiment, two adjacent primary loop circuits provide for quadrature radio frequency transmission to and from the resonator coil at a first frequency and the other two primary loop circuits provide for quadrature radio frequency transmission to and from the resonator coil at a second resonance frequency. Each of the primary loop circuits includes a tank circuit (62) for blocking the passage of the frequency of the other quadrature primary loop circuit pair.

Abstract: In a magnetic resonance imaging apparatus, a first frequency radio signal source (20a) is connected in quadrature with a four fold symmetric birdcage coil (24) at 90.degree. spaced connection points (80a,b). A source of a second radio frequency signal is directly connected with the birdcage coil by first and second inductive couplings (70a,b). The birdcage coil includes tank circuits (52) and capacitors (58, 60) in the end connectors. The capacitance of the end connectors is simultaneously adjustable by a tuning ring (62) to adjust a first resonance frequency of the coil and the capacitance of the tank circuits is selectively adjustable to adjust a second resonant frequency of the birdcage coil. In this manner, the birdcage coil is simultaneously tuned to two frequencies and can operate in quadrature at either one.

Abstract: A resonance exciting coil (C) excites magnetic resonance in nuclei disposed in an image region in which a main magnetic field and transverse gradients have been produced. A flexible receiving coil (D) includes a flexible plastic sheet (40) on which one or more loops (20) are adhered to receive signals from the resonating nuclei. Velcro straps (46) strap the flexible sheet and the attached coil into close conformity with the surface of the portion of the patient to be imaged. An impedance matching or coil resonant frequency adjusting network (50) is mounted on the flexible sheet for selectively adjusting at least one of an impedance match and the peak sensitivity resonant frequency of the receiving coil. A preamplifier (52) amplifies the received signals prior to transmission on a cable (24). A selectively variable voltage source (70) applies a selectively adjustable DC bias voltage to the cable for selectively adjusting at least one of the impedance match and the LC resonant frequency of the receiving coil.

Abstract: A resonance exciting coil (C) excites magnetic resonance in nuclei disposed in an image region in which a main magnetic field and transverse gradients have been produced. A flexible receiving coil (D) includes a flexible plastic sheet (40) on which one or more loops (20) are adhered to receive signals from the resonating nuclei. Velcro straps (46) strap the flexible sheet and the attached coil into close conformity with the surface of the portion of the patient to be imaged. An impedance matching or coil resonant frequency adjusting network (50) is mounted on the flexible sheet for selectively adjusting at least one of an impedance match and the peak sensitivity resonant frequency of the receiving coil. A preamplifier (52) amplifies the received signals prior to transmission on a cable (24). A selectively variable voltage source (70) applies a selectively adjustable DC bias voltage to the cable for selectively adjusting at least one of the impedance match and the LC resonant frequency of the receiving coil.

Abstract: During a transmit cycle portion, a radio frequency transmitter (C) continuously generates an AC biasing signal and selectively generates a radio frequency signal. The AC biasing signal gates a first switch (10) and a second switch (32) such that the radio frequency signals from the transmitter are conducted to a magnetic resonance probe (E) but are blocked from being conducted to a receiver (F). A first filter (20) prevents the bias signals from being applied to the probe. The second switch includes a pair of crossed diodes (34, 36) which are gated conductive by the AC bias signal. A filter (72) passes the radio frequency signals but not the bias signals to ground to prevent the radio frequency signals from reaching the receiver. A filter (80) allows the bias signals to be applied across a load (88) such that the transmitter sees the load at the bias signal frequency. Another filter (40) prevents the bias signal from reaching the transmitter.