Gradient coil, magnetic resonance imaging device, and method for designing coil pattern

A gradient magnetic field coil, comprising:

• a first coil in a tube shape, the first coil generating linear magnetic field distribution in an image capturing region of a nuclear magnetic resonance imaging device;
• and
• a second coil in a tube shape, the second coil being arranged outside the first coil and inside a static magnetic field coil device, generating a static magnetic field with uniform magnetic field distribution in the image capturing region, and reducing a leakage magnetic field that is from the first coil to the static magnetic field coil device,
• wherein a cross-section, of the second coil, perpendicular to an axis of the tube shape of the second coil is substantially circular, and a cross-section, of the first coil, perpendicular to an axis of the tube shape of the first coil is not circular,
• and wherein the first coil and/or the second coil is arranged in multiplication, and a number of turns is different between the first coil and the second coil of each of two gradient magnetic field coils inclined in respective directions different from an axial direction.

A gradient magnetic field coil, comprising:

• a first coil in a tube shape, the first coil generating linear magnetic field distribution in an image capturing region of a nuclear magnetic resonance imaging device;
• and
• a second coil in a tube shape, the second coil being arranged outside the first coil and inside a static magnetic field coil device, generating a static magnetic field with uniform magnetic field distribution in the image capturing region, and reducing a leakage magnetic field that is from the first coil to the static magnetic field coil device,
• wherein a cross-section, of the second coil, perpendicular to an axis of the tube shape of the second coil is substantially circular, and a cross-section, of the first coil, perpendicular to an axis of the tube shape of the first coil is not circular,
• wherein the first coil and/or the second coil is arranged in multiplication,
• wherein the first coil and the second coil of each of two gradient magnetic field coils that are inclined in respective directions different from an axial direction have turns in a spiral shape,
• and wherein an elliptical degree of a second turn counted from a center of the second coil has a difference greater than or equal to 20%.

A gradient magnetic field coil, comprising:

• a first coil in a tube shape, the first coil generating linear magnetic field distribution in an image capturing region of a nuclear magnetic resonance imaging device;
• and
• a second coil in a tube shape, the second coil being arranged outside the first coil and inside a static magnetic field coil device, generating a static magnetic field with uniform magnetic field distribution in the image capturing region, and the second coil reducing a leakage magnetic field that is from the first coil to the static magnetic field coil device,
• wherein a plurality of turns disposed in multiplication for a coil pattern of the first coil and/or the second coil is arranged such that a crossover wire connects neighboring turns with each other, a return wire is connected with an inside turn, and each crossover wire portion intersecting the return wire is serpentine.

A gradient magnetic field coil, comprising:

• a first coil in a tube shape, the first coil generating linear magnetic field distribution in an image capturing region of a nuclear magnetic resonance imaging device;
• and
• a second coil in a tube shape, the second coil being arranged outside the first coil and inside a static magnetic field coil device for generating a static magnetic field with uniform magnetic field distribution in the image capturing region, and the second coil reducing a leakage magnetic field that is from the first coil to the static magnetic field coil device,
• wherein a plurality of turns disposed in multiplication for a coil pattern of the first coil and/or the second coil is arranged such that a crossover wire connects neighboring turns with each other, a return wire is connected with an inside turn, and a width of each crossover wire intersecting the return wire is larger than or equal to four times and smaller than or equal to ten times a width of the return wire.

A gradient magnetic field coil, comprising:

• a first coil in a tube shape, the first coil generating linear magnetic field distribution in an image capturing region of a nuclear magnetic resonance imaging device;
• and
• a second coil in a tube shape, the second coil being arranged outside the first coil and inside a static magnetic field coil device, generating a static magnetic field with uniform magnetic field distribution in the image capturing region, and the second coil reducing a leakage magnetic field that is from the first coil to the static magnetic field coil device,
• wherein turns arranged in multiplication for a coil pattern of the first coil or the second coil are connected with a current supply wire and a return wire, and one section of the each turn intersecting with the current supply wire and the return wire which are arranged adjacent to each other is bypassing.

A method for designing coil pattern of at least one of a first coil in a tube shape, the first coil generating linear magnetic field distribution in an image capturing region of a nuclear magnetic resonance imaging device, and a second coil in a tube shape, the second coil reducing a leakage magnetic field that is from the first coil to a static magnetic field coil device for generating uniform magnetic field distribution in the image capturing region, the method for designing comprising:

• representing an initial value of current distribution on a current carrying surface of at least one of the first coil and the second coil, by a current potential vector assigned to nodes of finite surface elements;
• representing a target magnetic field at a plurality of magnetic field evaluation points which are set on at least one of the image capturing region and the static magnetic field coil device, by a magnetic field vector;
• obtaining singular values, a group of eigen vectors of magnetic field distribution, and a group of eigen vectors of current potential, by a response matrix from the current potential vector to the magnetic field vector and singular value decomposition of the response matrix;
• setting a difference between the target magnetic field and an initial value of the magnetic field vector as a difference target magnetic field;
• and
• representing an approximated value of a current potential vector that generates the difference target magnetic field, by a polynomial of the group of eigen vectors of the current potential, and determining coefficients of respective terms of the polynomial, based on the singular values and the group of eigen vectors of the magnetic field distribution.