Abstract: A magnetic resonance imaging apparatus includes main field coils (10) for generating a temporally uniform magnetic field longitudinally through a central bore (12). A whole body gradient magnetic field coil (30) and radio frequency coil (36) are disposed around the bore. An insertable coil assembly (40) includes an insertable gradient coil, a radio frequency coil (74) and a radio frequency shield (76). The insertable gradient coil includes a pair (62, 64) of x-gradient windings (FIGS. 3 and 4), a pair (66, 68) of y-gradient windings (FIGS. 5 and 6), and a pair (70, 72) of z-gradient windings (FIGS. 7 and 8), which are wrapped around inner and outer surfaces of a dielectric former (60). The x, y, and z insertable gradient coil pairs are configured such that they generate uniform magnetic field gradients within the insertable coil assembly when its central axis is positioned transverse to the direction of the temporally uniform magnetic field generated by the main field coils.

Abstract: A superconducting magnet (10) generates a uniform, static magnetic field through a central bore (12) along its longitudinal or z-axis. An insertable coil assembly (40) is inserted into the bore with a radio frequency shield (76, 84) for providing a radio frequency shield between the insertable coil assembly and a surrounding, whole body radio frequency coil assembly (32) and a whole body gradient magnetic field coil assembly (30). The insertable coil includes a gradient coil (44a) including conductors (52) mounted on a dielectric former (50) with a dielectric constant below 4.0. The conductors are relatively narrow and spaced relatively far apart to minimize capacitive coupling with a closely adjacent insertable radio frequency coil (70a). Filters (60, 64) are connected with the conductors of the gradient coil to prevent the gradient coil conductors from supporting radio frequency signals while permitting ready support of kHz frequency currents.

Abstract: A magnetic resonance imaging apparatus includes main field coils (10) for generating a temporally uniform magnetic field longitudinally through a central bore (12). A whole body gradient magnetic field coil (30) and radio frequency coil (36) are disposed around the bore. An insertable coil assembly (40) includes an insertable gradient coil (42) and a radio frequency coil (44). The insertable coil assembly place the gradient and radio frequency coil significantly closer to the region of interest to be imaged than the whole body coils. In the embodiment of FIG. 2, the gradient coil assembly is a cylindrical coil assembly including x, y, and z-gradient coils which receive current pulses in order to generate linear, uniform, magnetic field gradients through a selected region adjacent a patient end of the gradient coil.

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 magnet assembly (10) generates a temporally constant magnetic field through a central bore (12). A whole body gradient coil assembly (30) and a whole body radio frequency coil (36) are mounted in the central bore. A insertable gradient coil assembly (40), such as a head gradient coil, is selectively insertable into and removable from the bore (12). The insertable gradient coil assembly generates linear magnetic field gradients (90) within its bore for encoding magnetic resonance excited and manipulated by radio frequency signals from the whole body radio frequency coil. In regions (96) outside of the insertable gradient coil, the insertable gradient coil produces magnetic field gradients of the same strength as magnetic field gradients generated within its bore. Resonating dipoles within regions (96) contribute encoded magnetic resonance signals which are indistinguishable from the encoded magnetic resonance signals generated from within the insertable gradient coil bore.

Abstract: A magnetic resonance imaging machine includes a toroidal vacuum dewer (24) which contains a superconducting magnet (10). A radio frequency coil (32) is mounted within a cylindrical bore (26) of the vacuum dewer. A cylindrical, dielectric former (46) supports an RF shield (34), a z-gradient coil (50), an x-gradient coil (52), and a y-gradient coil (54). The x and y-gradient coils are each composed of four like spiral coil constructions. A metallic layer is cut with cut lines (64) to define a generally spiral coil winding pattern. In a high current density region (68) in which the coil windings are narrower than a preselected width, the cut lines (76) are thinner. In lower current density regions (70), the cut lines (78) are thicker. In lower current density regions, two cut lines are defined between adjacent coil windings such that the coil windings are limited to a maximum width.

Abstract: A readily manufacturable dispenser for roll tissue paper enables use of the paper for general household purposes. First and second parts include longitudinally extending mandrel portions for receiving the roll of tissue that is dispensed through an orifice in the side of the dispenser. The two parts of the dispenser are locked together by an O-ring friction seal between their respective mandrel portions. Knockout tabs in the dispenser end walls enable adaptation to a conventional bathroom fixture.

Abstract: The magnetic field assembly of a magnetic resonance imaging device includes an annular superconducting magnet (10) which is mounted within a toroidal vacuum vessel (24). A cylindrical member (26) defines a central bore through which the superconducting magnets generate a temporally constant primary magnetic field. A cylindrical, dielectric former (46) is mounted in the bore displaced a small distance from the cylindrical member. A radio frequency coil (32) is mounted within the cylindrical member defining a patient receiving examination region. An RF shield (34) is mounted around the exterior peripheral surface of the former. Primary gradient coils (40) are mounted around and potted to the exterior of the dielectric former around the RF shield. Gradient shield or secondary coils (44) are potted around an exterior of the cylindrical member within the vacuum chamber. As illustrated in FIG.

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: Superconducting magnets (10) of a magnetic resonance imager create static magnetic fields through an examination region (12). Gradient magnetic field coils (30) under control of a gradient magnetic field control (42) generate gradient magnetic fields across the examination region (12), as a whole. A plurality of surface coils (36, 38) receive radio frequency signals from each of two distinct subregions within the examination region (12). The two receiver coils are connected with separate receivers (60.sub.1, 60.sub.2) which demodulate the received magnetic resonance signals. The magnetic resonance signals are reconstructed (76) into an image representation (80, 82) of the first and second subregions. In the embodiment of FIGS. 1 and 2, a radio frequency transmitter (40) and a whole body coil (32) generate and manipulate the magnetic resonance signals within the first and second subregions. In the embodiment of FIGS. 3 and 4, a plurality of transmitters (40.sub.1, 40.sub.2, . . .

Abstract: An examination region (12) is defined within the bore of a superconducting magnet assembly (10). An RF coil (22) and gradient magnetic field coils (14) are disposed within the bore of the superconducting magnet assembly around the examination region. The superconducting magnet includes a hollow, cylindrical vacuum vessel (40). An annular, liquid helium holding low temperature reservoir (60) extends centrally through the vacuum vessel, but is sealed therefrom such that liquid helium is not drawn into the vacuum. A plurality of annular superconducting magnets (56) are received in the low temperature reservoir immersed in the liquid helium. A first cold shield (44) and a second cold shield (50) are mounted in the vacuum vessel surrounding the low temperature reservoir. A main magnetic field shield coil (66) is disposed in the low temperature reservoir outside of the annular superconducting magnets for canceling the magnetic field generated by the annular magnets surrounding the magnet.

Abstract: A superconducting magnet (10) generates a uniform, static magnetic field through a central bore (12) along its longitudinal or z-axis. A biplanar gradient coil assembly (44) is inserted into the bore to create gradients across the static magnetic field along orthogonal x, y, and z-axes. A biplanar radio frequency coil assembly (50, 80) is inserted into the bore for transmitting radio frequency signals into a subject and receiving magnetic resonance signals from the subject. The radio frequency coil includes a first biplanar coil assembly (50) for generating RF signals in an x-direction and a second biplanar coil assembly (80) for generating RF signals in a y-direction. The two biplanar coil assemblies each include a plurality of conductors (52, 82) along a first plane and a second plurality of conductors (54, 84) along a parallel second plane. The conductors extend parallel to the z-direction.

Abstract: An examination region (12) is defined within the bore of a superconducting magnet assembly (10). An RF coil (22) and gradient magnetic field coils (14) are disposed within the bore of the superconducting magnetic assembly around the examination region. The superconducting magnet includes a hollow, tubular vacuum vessel (40) which contains a plurality of annular superconducting magnets (58). These superconducting magnets are held in a liquid helium holding reservoir (60) such that they are held below their superconducting temperature. A first cold shield (44) and a second cold shield (50 ) have tubular portions between the superconducting magnets and the examination region. These cylindrical portions each include a cylinder (70) of a electrically insulating material such as reinforced plastic. Thermally conductive layers (72) are defined on each surface and are divided by etched slots or resistance portions (74) into a multiplicity of elongated narrow segments (92).

Abstract: An examination region (12) is defined along a z-axis offset from a geometric center (30) of a gradient coil assembly (20). Cylinders of a non-conductive, non-magnetic material support x, y, and z-gradient coils (24, 26, 22) for causing orthogonal magnetic field gradients through the offset examination region. The z-gradient coil (FIG. 2 ) includes a plurality of distributed loop arrays with a winding pattern selected to cause a region of linear magnetic field gradients in the z-direction in a region offset toward a cylinder first end (32). The x and y-gradient coils each include two pairs of oppositely disposed windings (FIG. 3 ) which include a pair of inner spirals (96, 98) offset towards the first end of the cylinder and an outer spiral (90) extending therearound. The outer spiral bows in (92) toward the cylinder first end and fans out (94) toward the second end.

Abstract: An examination region (12) is defined by an elliptically crossed-section cylinder (20) of a non-conductive, non-magnetic material. The x, y, and z-gradient coils (24, 26, 22) are mounted on elliptically crossed-section cylindrical surfaces along the former for causing gradient magnetic fields within the examination region. Each of the x, y, and z-gradient coils includes a plurality of arrays or groups of coil loops. The arrays of coil loops are symmetric about a central plane of symmetry. To either side of the plane of symmetry, each of the first of the x, y, and z coil arrays (74, 80, 90) include at least a first group of loops in which current flows in a clockwise direction and a second array of loops (76, 82, 90) in which current flows in an opposite direction.

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: An incomplete set of magnetic resonance image data is collected and stored in a view memory (40). The incomplete set of image data includes a central or first set of data values (42, 42') and half of the remaining data values (44, 44'). A symmetric data set which fills the other remaining half (46, 46') of the data values is generated (90) by determining the complex conjugate of each value of the incomplete data set. The incomplete and symmetric data sets are Fourier transformed (64, 94) to create first and second images f.sub.1 (x,y) and f.sub.2 (x,y). The first and second images are multiplied (100, 104) by conjugately symmetric phase correction values e.sup.i.phi.(x,y) and e.sup.-i.phi.(x,y) from a phase correction memory (70) to produce phase corrected images. The first and second phase corrected image representations are summed (110) and displayed (114). The phase correction values .phi.

Abstract: A magnetic resonance imager includes a quadrature coil assembly (20) for transmitting radio frequency signals into and receiving magnetic resonance signal from an examination region. The quadrature coils assembly includes a first coil (22) and a second coil (24). A shunt path (32, 64, 74, 84, 94, 98, 100, 112, 114, 122) provides a current path by shunting at least a portion of one of the coils. A variable impedance (34, 66, 76, 86, 96, 110, 120) adjusts the amount of current flow through the shunt path and the current flow through the bypassed coil portion. More specifically, adjusting the impedance changes the magnetization vector generated by the coil assembly in a transmit mode and adjusts their relative isolation in a receive mode. The quadrature coils are mounted such that they are offset by about, but not quite, 90.degree.. The variable impedance is adjusted until the offset is brought precisely to 90.degree..

Abstract: Magnets (12) create a main magnetic field along a z-axis through an image region. A localized coil (D) is disposed in the image region at least to receive magnetic resonance signals from nuclei of the subject which have been induced to resonance. The localized coil includes an inner conductor (30), preferably a plate, which defines a current path extending along the z-axis. The inner conductor is mounted closely adjacent and parallel to a surface of the subject. An outer conductor (32), preferably also a plate, is mounted parallel to but further from the subject than the first conductor. A connecting member (34) interconnects a first end of the inner and outer conductors and is disposed perpendicular to the z-axis. A matching circuit (36) including capacitors (50) which define the resonant frequency of the coil are connected adjacent second ends of the inner and outer conductors.

Abstract: Magnet (12) creates a main magnetic field along a z-axis through an image region. A localized coil (D) is disposed in the image region at least to receive magnetic resonance signals from nuclei of the subject which have been induced to resonance. The localized coil includes an inner conductor (30), an outer conductor (32), and a dielectric material (52) therebetween. The outer conductor defines a gap (50) midway between its ends. One end of the inner conductor is connected with a gate of an FET transistor (66) and the outer conductor is connected with its source. The transistor source and drain are connected by a coaxial transmission cable (38) with a DC power supply (70) which provides a DC bias across the transistor source and drain. The cable also connects the transistor with a radio frequency receiver (40) to convey preamplified magnetic resonance signals thereto.