METHOD FOR DESIGNING GRADIENT COILS FOR MRI SYSTEMS, GRADIENT COILS FOR MRI SYSTEMS OBTAINED BY THE SAID METHOD AND MRI SYSTEM COMPRISING SUCH GRADIENT COILS
First Claim
1. Method for designing gradient coils,the gradient coils providing for a current distribution on the lateral surface of an elliptical cylinder generating a field being perpendicular to the longitudinal axis of the elliptical cylinder,the method comprising 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.
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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.
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Citations
23 Claims
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1. Method for designing gradient coils,
the gradient coils providing for a current distribution on the lateral surface of an elliptical cylinder generating a field being perpendicular to the longitudinal axis of the elliptical cylinder, the method comprising 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. - View Dependent Claims (2, 3, 4)
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- 5. Gradient coils in combination with the magnet of an MRI system, the gradient coils being driven by a control unit for generating gradient fields along three Cartesian axis, the said magnet fields permeating a region of interest, the said gradient coils comprising discrete winding patterns configured to generate a current distribution on the surface of an elliptical cylinder the magnet of the MRI system generating a static magnetic field oriented perpendicular to the longitudinal axis of the said elliptic cylindrical surface.
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21. An MRI system comprising:
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a gantry for accommodating a target body under examination or a part thereof; a magnet for generating a static magnetic field in a volume of space; gradient coils for generating gradient magnetic fields in addition to the static magnetic field according to three spatial directions; a control unit configured to drive and control the gradient coils and the magnet; a transmission antenna connected to an excitation signal sequence generator for transmitting spin echo excitations signals into the cavity housing the target body; a receipt antenna for receiving the MRI signals caused by the excitation signals; an MRI receipt signals processing unit and image generation unit for processing the signals and extracting image data information and for generating the images; a display unit for displaying the reconstructed images; a control unit managing the excitation signal sequence generator, the receipt signals processing unit, image generation unit and the display; a user interface for input of MRI image acquisition settings to be specified by the user before starting with the image acquisition session. - View Dependent Claims (22, 23)
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Specification