Picker International, Inc.

David A Lampman

Michael Andrew Morich

James M McNally

Labros S Petropoulos

Paul T Orlando

Benjamin R Stern

Martyn N Paley

John Lester Patrick

Wayne R Dannels

Mehrdad Mehdizadeh

Haiying Liu

David A Molyneaux

Mark A Richard

Xueming Zou

James B Murdoch

Nicholas J Mastandrea, Jr

John D Schellenberg

Gregory C Hurst

Kenneth S Foster

Terrence J Brovost

A diagnostic imaging apparatus such as a magnetic resonance imaging (MRI) device includes a gradient coil assembly (,) and an RF coil (,) disposed proximate pole faces (,). An interventional head coil assembly (,) includes a base (,), a head frame housing (,) including at least one first conductor (,) associated therewith, a first mount (,) that connects the head frame housing (,) to the base (,), a bridge housing (,) including at least one second conductor (,) associated therewith, and a second mount (,) that connects the bridge housing (,) to the head frame housing (,) thereby coupling the at least one first conductor (,) to the at least one second conductor (,) to form a surface coil for use in imaging an object attached to the head frame housing (,).

Interventional radio frequency coil assembly for magnetic resonance (MR) guided neurosurgery

An apparatus (1) for supporting a surgical instrument in the operative environment of an imaging device comprises components all made of a material compatible for use in the operative environment of the imaging device. The components of the apparatus (1), made of such a material, include a member (32) that has a spherical surface and includes a bore (50) extending through the member along its diameter. A grip (26) has a grip surface (40) defining an aperture that is adapted to receive the member for rotatable movement within the aperture. The grip (26) extends around the member (32) in a circumferential path and has a gap (42) therein. A fastener (30) is operatively connected to the grip (26). The fastener (30) is adjustable to change the size of the gap (42) and adjust the compressive force applied to the received member (32) in the grip.

MR compatible neurosurgical positioning apparatus

A magnetic resonance imaging apparatus includes a main field magnet (12) for generating a temporally constant magnetic field through an examination region. A radio frequency transmitter (84) excites and manipulates magnetic resonance in selected dipoles in the examination region. A receiver (90) demodulates magnetic resonance signals received from the examination region, a processor (74) reconstructs the demodulated resonance signals into an image representation. A plurality of fingerprint gradient magnetic field coils (24, 26) induce gradient magnetic fields across the temporally constant magnetic field. Each of the fingerprint gradient coils (24, 26) includes a generally spiral winding (32A-32D) having a first crossectional dimension (H) perpendicular to the temporally constant magnetic field which is at least twice a second crossectional dimension (W) in a direction parallel to the temporally constant magnetic field.

Gradient coils with reduced eddy currents

Magnetic resonance imaging data of a volume of interest is collected by applying a radio frequency pulse (70, 96) and following the pulse with gradients applied along three axes (x,y,z). The gradients along x and y-axes are generally sinusoidal, which sinusoids increase and decrease in magnitude to define beat patterns of a common period. The period of the first and second gradients is an integer multiple of the gradient along the z-axis. In the embodiment of FIGS. 2A and 2B, the beats of the first and second gradients increase linearly and the third gradient oscillates in a linearly expanding generally sinusoidal pattern such that k-space is traversed by a trajectory that spirals around a series of spheres (50, 52, 54, 56, 58, 60) of progressively smaller radius. Blips or spikes (78) are preferably applied between each half cycle of the third gradient to step the trajectory to the radius of the next concentric sphere. In the embodiment of FIGS. 3A and 3B, the magnitude of the beats of the first and second gradients remain substantially constant and the gradient pulses along the third axis are applied generally between and at the mid-point of each beat such that the trajectory through k-space follows a series of parallel spirals lying along a cylinder. In the embodiment of FIGS. 4-4D, the beat patterns again increase linearly and the third gradient alternates polarity with each half beat such that the trajectory through k-space spirals around a series of concentric cones.

Three-dimensional spiral echo volume imaging

An insertable coil (40) is inserted in a bore (12) of a magnetic resonance imaging apparatus. Primary field magnets (10) create a temporally constant magnetic field longitudinally through the insertable coil. A computer control (58) controls a radio frequency coil (44) and a gradient coil (42) to create magnetic resonance imaging sequences and process received magnetic resonance signals into image representations. The insertable gradient coil includes a central cylindrical portion (60) having a first circumference. A second portion (62) disposed toward a patient receiving end of the insertable coil has a second circumference which is larger than the first circumference. In this manner, the first, smaller circumferential portion is adapted to receive the patient's head and the larger circumferential portion is adapted to accommodate the patient's shoulders. For symmetry which eliminates magnetic field induced torques, a service end (68) matches and is symmetric to the patient end (62). The z-gradient coil windings (FIG. 3), and x and y-gradient coil windings (FIGS. 4 or 5) are mounted such that a portion of the windings are on the first, smaller circumferential portion and a portion of the windings are on the larger patient and service end portions.

Wide aperture gradient set

An insertable coil (40) is inserted in a bore (12) of a magnetic resonance imaging apparatus. Primary field magnets (10) create a temporally constant magnetic field longitudinally through the insertable coil. A computer control (58) controls a radio frequency coil (46) and a gradient coil (42) to create magnetic resonance imaging sequences and process received magnetic resonance signals into image representations. The insertable gradient coil includes a cylindrical, dielectric former (44) of appropriate diameter to receive a patient's head. A pair of parabolic cutouts (62) are defined adjacent a patient receiving end of the dielectric former and are of an appropriate size to receive the patient's shoulders. In this manner, the patient's head can be centered in a longer head coil. Four thumbprint type x-gradient coil windings (72) are mounted symmetrically on the dielectric former with the parabolic cutouts (74) centrally on one side of the thumbprint coil windings. The windings of the thumbprint coils are contoured to follow the parabolic cutout. Four y-gradient coil windings (84) rotated 90.degree. from the x-gradient coils are mounted on the dielectric former. The y-gradient thumbprint coil windings are mounted between the parabolic cutouts and windings along their corners (82) conform to the parabola.

Magnetic resonance insert gradient coils with parabolic returns for

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. The whole body gradient coil assembly (30) generates magnetic field gradient pulses concurrently with RF pulses from the whole body gradient coil (36) to saturate material in the aliasing regions ( 96) or selected aliasing region portions (100) within which there are dipoles that contribute aliasing resonance signal components.

Technique for reducing aliasing artifacts wtih insertable gradient coils

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. In another embodiment, the third and fourth primary loop circuits are connected with tuning capacitors for adjusting the resonance frequency of the resonator coil relative to radio frequency signals applied and received by the primary loop circuit 180.degree. opposite. This enables the frequency of each quadrature component of a quadrature RF signal to be adjusted separately. Analogously, this enables the resonance frequency of two linear RF signals to be adjusted independently.

Technique for driving quadrature dual frequency RF resonators for

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. PIN diodes (92) are provided for de-tuning the coil such that it operates in a third mode in which no resonance frequency exists such that the birdcage coil does not interfere with reception of resonance signals by a surface coil (42). When operating in quadrature, additional PIN diodes (114) are provided for connecting the RF feed point to one node (102a) of a 90.degree. phase shift circuit (100) in the transmit mode and to the opposite node (102b) of the 90.degree. phase shift circuit in the receive mode.

NMR spectroscopy and imaging coil

RF and gradient pulse combinations (30, 32, 36, 38) are applied to limit or define a region of interest in two dimensions (42) by pre-saturating surrounding regions (34a, 34b, 40a, 40b). A 90.degree. RF pulse (50) is applied in the presence of a slice select gradient (60) to excite selected dipoles in a slice or slab, defining the region of interest or voxel in the third dimension. Phase encoding gradients (62) and (64) are applied to encode spatial position in two dimensions of the slice. A binomial refocusing pulse (52) suppresses the water and refocuses the metabolite resonance into an echo which is acquired (68) by a receiver (26). A Fourier transform means (72, 74) transforms the received magnetic resonance signals to create a two dimensional array (76) or matrix of spectra (78) corresponding to a two dimensional array of spatial positions within the slice. A third phase encode gradient (66) may be applied to encode the regionof interest in three dimensions for generating a three dimensional array of the spectra.

Multi-axis pre-saturated spin echo phase encoded spectroscopy

Magnetic resonance is excited in first selected dipoles and suppressed in second selected dipoles in an examination region (10) by the application of a binomial 90.degree. pulse (40). The induced resonance is phase encoded along at least two axes by phase encode gradients (42, 44). Concurrently, an RF refocussing pulse (54) and a slice select gradient pulse (56) are applied. Analogous pulse pairs (68, 70; 72, 74) are applied once with the slice select gradient along each of three mutual orthogonal axes such that a voxel or volume defined by the intersection of the three slices is defined. A magnetic resonance echo (84) is allowed to form, which echo is attributable to the resonating dipoles within the defined voxel. The phase encoding gradients have divided the voxel into subvoxels along the respective axes. The resultant magnetic resonance echo signals are Fourier transformed (92) into sets of chemical spectra corresponding to each subvoxel and displayed in a two dimensional image representation on a video monitor (96).

NMR spectroscopy with phase encoding within a selected voxel

In-slice magnetic resonance is excited with a 90.degree. RF pulse (50, 50'). A 180.degree. RF pulse (56, 56') is applied to cause a magnetic resonance spin echo (58, 58'). However, the 180.degree. pulse also induces resonance in material outside the selected slice. The out-of-slice data is superimposed on the magnetic resonance spin echoes. Two views of magnetic resonance data are collected with the same phase encode gradient and stored temporarily in first and second memories (72, 74). The views are combined (76) such that the out-of-slice data sums and the in-slice data cancels. The magnitude of the out-of-slice data is magnitude adjusted (78) to create an out-of-slice magnetization view which is stored in an out-of-slice magnetization memory (80). A plurality of views with different phase encode gradients are subsequently collected during a magnetic resonant imaging sequence. Each view is subtracted from (90) the out-of-slice data view and transformed (92) into an image representation.

Out-of-slice artifact reduction technique for magnetic resonance imagers

A gradient field controller (30) generates current pulses with a preselected profile. Eddy current compensation circuits (42) alter the current pulse profile by adding additional components of selectable frequencies with selectable amplitudes or gains. A power amplifier (32) amplifies the modified current pulse and applies them to gradient field coils (34) of a magnetic resonance imager. A probe or coil (50) monitors the induced gradient response which is integrated (52) to provide an electronic representation of the induced gradient profile. A least squares analysis routine (72) determines the time constant and amplitude of a component attributable to a first eddy current which degrades the induced gradient profile. A filter frequency correction factor calculating routine (76) calculates appropriate filter frequency settings and a gain calibration factor calculating routine (78) calculates the gain settings for the compensation circuits (42). In operation, a repetitive correction sequence is implemented in which a current pulse is applied, the induced gradient field monitored, the longest time constant and the corresponding amplitude are determined, and appropriate adjustments to the calibration circuits are determined. The correction sequence is repeated, each time monitoring a shorter time constant eddy current until the profile of the induced gradient substantially conforms to a preselected profile.

Automatic eddy current correction

A binomial pulse generator (32) selectively generates binomial radio frequency excitation pulses (60) which induce magnetic resonance only in selected hydrogen dipoles and suppresses resonance in others. An inversion pulse generator (34) generates a first inversion pulse (70) in the presence of a first magnetic field gradient (72) generated by a gradient control (22). The inversion pulse only inverts the magnetization of resonating nuclei in a first plane defined by the first magnetic field gradient. A second inversion pulse (74) applied in the presence of a second magnetic field gradient (76) inverts the magnetization of resonating nuclei in a second planar region defined by the second magnetic field gradient. A third inversion pulse (78) applied concurrently with a third magnetic field gradient (80) inverts the magnetization of resonating nuclei in a third planar region defined by the third magnetic field gradient. Only resonating nuclei in a volumetric element defined at the intersection of the first, second, and third planes are inverted all three times. The magnetization of other dipoles will have dephased differently from the dipoles in the volumetric element. In this manner, only the dipoles in the volumetric element contribute to a spin echo (82) which follows the third inversion pulse. Data acquired during the third spin echo may be spectrographically analyzed to determine the chemical composition within the volumetric element. Alternately, a phase encoding gradient (90) and a read gradient (92) may be applied as part of the sequence to provide the appropriate phase encoding to the acquired data such that the acquired data can be reconstructed into an image representation.

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Lakewood, OH, United States of America

David A Lampman