US 5,177,441 AGranted

Elliptical cross section gradient oil

AssigneePicker International, Inc.

InventorsMichael A. Morich, John L. Patrick, Labros Petropoulos, Michael A. Martens, Robert W. Brown

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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.

Claims17

Dependent claims

A magnetic resonance imaging apparatus comprising:

a main magnetic field means for generating a main magnetic field longitudinally through an examination region generally parallel to a longitudinal z axis, the examination region having a generally elliptical cross-section with an x axis being defined along a major axis of the elliptical cross-section and a y axis being defined perpendicular to the x and z axes along a direction parallel to a minor axis of the elliptical cross section;
a magnetic field gradient means for generating magnetic field gradients across the examination region, the gradient magnetic field means including:
first and second coil loop arrays disposed symmetrically on opposite sides of an x-y plane of symmetry and along an elliptical cross-section cylindrical surface surrounding the examination region,
third and fourth coil loop arrays disposed symmetrically about the x-y plane of symmetry along the elliptical cylindrical surface and more remote from the plane of symmetry than the first and second coil loop arrays, respectively, the third and fourth coil loop arrays further being disposed symmetric relative to at least one of an x-z plane and a y-z plane,
a current supply means for supplying electric current to the coil loop arrays such that the first and third coil loop arrays disposed to a first side of the plane of symmetry have net current flows in opposite directions and such that the second and fourth coil loop arrays disposed to a second side of the plane of symmetry have net current flow in opposite directions;
a magnetic resonance excitation means for selectively exciting magnetic resonance dipoles disposed in the examination region;
a magnetic signal receiving means for receiving magnetic resonance signals from the resonating dipoles;
and,
a reconstruction means for reconstructing an image representation from the magnetic resonance signals.

6 more elements

A magnetic resonance apparatus comprising:

a main magnetic field means for generating a main magnetic field along a z axis through an examination region;
an elliptical z-gradient coil assembly having coil windings extending peripherally around an elliptically cross-sectioned cylinder, the coil windings being disposed symmetrically on opposite sides of a plane of symmetry defined perpendicular to the z axis;
a current supply means for supplying electrical current to the coil windings such that the majority of coil windings on a first side of the plane of symmetry have a net current flow in first direction around a periphery of the elliptically cross-sectional cylinder and at least one of the windings on the first side of the plane of symmetry has a net current flow in a second direction opposite to the first direction and such that the majority of the coil windings on a second side of the plane of symmetry have a net current flow in the second direction and at least one of the coil windings on the second side of the plane of symmetry has a net current flow in the first direction;
a resonance excitation means for selectively exciting dipoles in the examination region to resonance;
and,
a magnetic resonance receiving means for receiving radio frequency magnetic signals emanating from the examination region.

3 more elements

Dependencies are inferred from the claim text.