Abstract: Method for shimming a magnetic field which is generated by a magnetic structure, and which permeates a volume of space uses the following steps: measuring the magnetic field in a region of a volume of space permeated by the said magnetic field; determining a parameter which is a measure of the homogeneity of the magnetic field; defining a distribution of correction elements including a predetermined number of magnetic dipoles each having a predetermined magnetic charge and a predetermined position relatively to the magnetic structure generating the magnetic field; calculating the charges of each of the dipoles and the position of each of the dipoles of a distribution which minimizes the parameter being a measure of the homogeneity of the magnetic field; using the distribution of dipoles as the shimming distribution of dipoles to be positioned on the magnetic structure.

Abstract: Shimming a magnetic field includes measuring the magnetic field and sampling it in a plurality of locations; defining a grid for positioning correction elements; calculating the position and magnitude parameters of one or more correction elements to obtain predetermined target values of the field characteristics, wherein an algorithm has been trained by a database of known cases in which each record links a certain initial magnetic field of a magnetic structure to the pattern of correction elements on a positioning grid for these correction elements in the magnet structure, thereby delivering as an output a pattern of correction elements on the positioning grid, which contributions to the magnetic field of the magnet structure generate a magnetic field which at least best approximates or meets the predetermined target values of the field characteristics.

Abstract: Magnetic field sensor, in particular for measuring magnetic noise fields caused by environmental magnetic noise in combination with MRI apparatus, the magnetic field sensor being further provided with field compensation coils assembly and with a compensation circuit driving the field compensation coils assembly to generate a magnetic field compensating the static magnetic field dissipating outside from the static magnetic field generator or from the gantry of the MRI apparatus at the position of the magnetic sensor. A method for operating the magnetic field sensor and a method and a system for compensation magnetic noise caused by environmental noise are also provided. An MRI apparatus is also disclosed comprising such a system and carrying out such a method for compensating magnetic noise fields.

Abstract: A method for designing gradient coils includes the following steps: a) defining an imaging volume as an ellipsoid; b) defining an elliptic-cylindrical surface enclosing the said ellipsoid; c) defining the current density at each point of the surface by a series of basis functions and corresponding coefficients expressed in elliptic cylindrical coordinates; d) describing the magnetic field generated at a generic point by the above defined current density integrated all over the said entire elliptic-cylindrical surface; e) determining the values of the coefficients of the basis functions by solving the inverse function for describing the magnetic field; f) generating a discrete winding patter of a gradient coil by using a stream function method from the continuous current density and by using a series of scattered contours of the stream function as the design of the winding patters according to a set total number of windings.

Abstract: Magnetic field sensor, in particular for measuring magnetic noise fields caused by environmental magnetic noise in combination with MRI apparatus, the magnetic field sensor being further provided with field compensation coils assembly and with a compensation circuit driving the field compensation coils assembly to generate a magnetic field compensating the static magnetic field dissipating outside from the static magnetic field generator or from the gantry of the MRI apparatus at the position of the magnetic sensor. A method for operating the magnetic field sensor and a method and a system for compensation magnetic noise caused by environmental noise are also provided. An MRI apparatus is also disclosed comprising such a system and carrying out such a method for compensating magnetic noise fields.

Abstract: A method for designing gradient coils includes the following steps: a) defining an imaging volume as an ellipsoid; b) defining an elliptic-cylindrical surface enclosing the said ellipsoid; c) defining the current density at each point of the surface by a series of basis functions and corresponding coefficients expressed in elliptic cylindrical coordinates; d) describing the magnetic field generated at a generic point by the above defined current density integrated all over the said entire elliptic-cylindrical surface; e) determining the values of the coefficients of the basis functions by solving the inverse function for describing the magnetic field; f) generating a discrete winding patter of a gradient coil by using a stream function method from the continuous current density and by using a series of scattered contours of the stream function as the design of the winding patters according to a set total number of windings.

Abstract: A shimming method for correcting inhomogeneity of a static magnetic field generated by a magnet of a nuclear magnetic resonance imaging machine includes: measuring the magnetic field at a plurality of points over a reference surface; generating a polynomial that solves Laplace's equation with boundary conditions given on the reference surface, the polynomial representing the magnetic field on the reference surface and having a plurality of harmonic terms, each associated with a coefficient; determining the coefficients from the field sampling values; defining a grid for positioning a plurality of correction elements and relating it to the field structure; and calculating the position and magnitude parameters of the correction elements, such that the correction elements affect the coefficients of the magnetic field to obtain the desired field characteristics, wherein the reference surface is a superquadric surface, such that the magnetic field is corrected in a volume delimited by the superquadric surface.

Abstract: The present invention relates to a method of correcting inhomogeneity of the static magnetic field generated by the magnet of a Nuclear Magnetic Resonance imaging machine, wherein the magnet is flat and the magnetic field on one side of said magnet is corrected such that a volume is defined, which is bounded by a spherical cap surface, in which volume and along which surface the magnetic field is homogeneous, i.e. has field lines having equal parallel directions and equal intensities.

Abstract: A Magnetic Resonance apparatus includes a 3D structure having a cavity for receiving a body under examination, a mechanism for generating a static magnetic field in the patient receiving cavity, a mechanism for generating variable magnetic fields in the cavity, an antenna for transmitting electromagnetic nuclear spin excitation pulses, an antenna for receiving the electromagnetic signals generated by nuclear spin relaxation, a plate for locating and fixing magnetic dipoles for fine correction of magnetic field homogeneity, and a compartment for the magnetic correction dipole locating and fixing plate, the compartment being adapted to be opened for direct access to the magnetic correction dipole locating and fixing plate from the outside. The compartment may be opened either by removal of an end plate of the magnetic field generating mechanism, or via a lateral slot for insertion and removal of the magnetic correction dipole locating and fixing plate.

Abstract: A shimming method for correcting inhomogeneity of a static magnetic field generated by a magnet of a nuclear magnetic resonance imaging machine includes: measuring the magnetic field at a plurality of points over a reference surface; generating a polynomial that solves Laplace's equation with boundary conditions given on the reference surface, the polynomial representing the magnetic field on the reference surface and having a plurality of harmonic terms, each associated with a coefficient; determining the coefficients from the field sampling values; defining a grid for positioning a plurality of correction elements and relating it to the field structure; and calculating the position and magnitude parameters of the correction elements, such that the correction elements affect the coefficients of the magnetic field to obtain the desired field characteristics, wherein the reference surface is a superquadric surface, such that the magnetic field is corrected in a volume delimited by the superquadric surface.

Abstract: The present invention relates to a method of correcting inhomogeneity of the static magnetic field generated by the magnet of a Nuclear Magnetic Resonance imaging machine, wherein the magnet is flat and the magnetic field on one side of said magnet is corrected such that a volume is defined, which is bounded by a spherical cap surface, in which volume and along which surface the magnetic field is homogeneous, i.e. has field lines having equal parallel directions and equal intensities.

Abstract: Method for making magnets particularly for the use in MRI scanners, which magnets are three-dimensional and have a tubular wall made of magnetized material, with a closed or open annular shaped cross-section, the tubular wall being composed of individual elements made of magnetized material, the magnetization of each element made of magnetized material having a predetermined direction in the transverse section plane and said directions being determined such to generate a uniform static magnetic field in the cavity of the tubular wall.

Abstract: An MRI apparatus having a magnet structure which delimits a cavity for receiving a body under examination or a part thereof, which includes a mechanism for generating a magnetic field in the cavity, as well as a mechanism for causing the body under examination or the part thereof to emit nuclear magnetic resonance signals, a region defined in the cavity, known as an imaging volume, and a mechanism for receiving the nuclear magnetic resonance signals. The geometric center of the geometric shape of the cavity delimited by the magnet structure is offset in relation to the geometric center of the imaging volume.

Abstract: An MRI apparatus including a magnetic structure defining a cavity for receiving a body under examination or a part thereof, a mechanism for generating a magnetic field inside the cavity, a mechanism for causing the body under examination or a part thereof to emit nuclear magnetic resonance signals, and a mechanism for receiving the nuclear magnetic resonance signals. The mechanism for generating the magnetic field includes one or more elements made of permanently magnetized material of the so-called superconducting bulk material type and, in combination therewith, a mechanism for keeping the magnetization condition of the superconducting bulk material which includes mechanisms for maintaining the temperature of the permanently magnetized material below the critical temperature thereof and for restoring the magnetization of the superconducting bulk material upon a complete or partial demagnetization.

Abstract: A Magnetic Resonance apparatus includes a 3D structure having a cavity for receiving a body under examination, a mechanism for generating a static magnetic field in the patient receiving cavity, a mechanism for generating variable magnetic fields in the cavity, an antenna for transmitting electromagnetic nuclear spin excitation pulses, an antenna for receiving the electromagnetic signals generated by nuclear spin relaxation, a plate for locating and fixing magnetic dipoles for fine correction of magnetic field homogeneity, and a compartment for the magnetic correction dipole locating and fixing plate, the compartment being adapted to be opened for direct access to the magnetic correction dipole locating and fixing plate from the outside. The compartment may be opened either by removal of an end plate of the magnetic field generating mechanism, or via a lateral slot for insertion and removal of the magnetic correction dipole locating and fixing plate.

Abstract: Method for making magnets particularly for the use in MRI scanners, which magnets are three-dimensional and have a tubular wall made of magnetized material, with a closed or open annular shaped cross-section, the tubular wall being composed of individual elements made of magnetized material, the magnetization of each element made of magnetized material having a predetermined direction in the transverse section plane and said directions being determined such to generate a uniform static magnetic field in the cavity of the tubular wall.

Abstract: An MRI apparatus comprising a magnet structure which delimits a cavity for receiving a body under examination or a part thereof, and which includes means for generating a magnetic field in said cavity, as well as means for causing the body under examination or the part thereof to emit nuclear magnetic resonance signals, a region being defined in the cavity, known as imaging volume, and means for receiving the nuclear magnetic resonance signals. The MRI apparatus also comprises an electronic processing unit with which the means for receiving the nuclear magnetic resonance signals are electrically connected; the cavity has an access opening for receiving a body under examination or part thereof. The geometric center of the geometric shape of the cavity delimited by the magnet structure is in offset relation to the geometric center of the imaging volume.

Abstract: An MRI apparatus including a magnetic structure defining a cavity for receiving a body under examination or a part thereof, a mechanism for generating a magnetic field inside the cavity, a mechanism for causing the body under examination or a part thereof to emit nuclear magnetic resonance signals, and a mechanism for receiving the nuclear magnetic resonance signals. The mechanism for generating the magnetic field includes one or more elements made of permanently magnetized material of the so-called superconducting bulk material type and, in combination therewith, a mechanism for keeping the magnetization condition of the superconducting bulk material which includes mechanisms for maintaining the temperature of the permanently magnetized material below the critical temperature thereof and for restoring the magnetization of the superconducting bulk material upon a complete or partial demagnetization.

Abstract: A method for determining construction parameters of magnet structures designed to generate magnetic fields in predetermined volumes of space, comprising the steps of: a) defining a predetermined volume of space in which a static magnetic field is to be generated; b) defining the nominal strength and profile of the magnetic field in said predetermined volume of space; c) mathematically describing the nominal magnetic field on the surface of and/or in said predetermined volume of space by using a polynomial expansion of the magnetic field-describing function, which provides a series of coefficients; d) determining the size, geometry and relative position in space of the means for generating said nominal magnetic field, with respect to the volume of space in and on which the desired, i.e. nominal magnetic field, is defined.

Abstract: A method for determining construction parameters of magnet structures designed to generate magnetic fields in predetermined volumes of space, comprising the steps of: a) defining a predetermined volume of space in which a static magnetic field is to be generated; b) defining the nominal strength and profile of the magnetic field in said predetermined volume of space; c) mathematically describing the nominal magnetic field on the surface of and/or in said predetermined volume of space by using a polynomial expansion of the magnetic field-describing function, which provides a series of coefficients; d) determining the size, geometry and relative position in space of the means for generating said nominal magnetic field, with respect to the volume of space in and on which the desired, i.e. nominal magnetic field, is defined.