Method for producing planar gradient coils for MRI systems, gradient coils produced by the said method and MRI system provided with the said gradient coils

Patent metadata

Field	Value
Publication number	US-12591027-B2
Application number	US-202418595893-A
Country	US
Kind code	B2
Filing date	Mar 5, 2024
Priority date	Mar 8, 2023
Publication date	Mar 31, 2026
Grant date	Mar 31, 2026

Abstract

A method for producing planar gradient coils for MRI systems includes defining a planar surface along which one continuous current wire extends along a path for generating a gradient field along a spatial direction; defining the path of the continuous current wire as a spiral path of a single continuous wire filament; describing the spiral path of the continuous current wire by a parametric curve according to a modified version of the Pascal Limaçons curve combined with the Archimede's spiral; applying the Biot-Savart law to evaluate the magnetic field generated by the continuous current wire extending along the spiral path; optimizing the parameters of the parametric curve for shaping the spiral path of the continuous current wire to generate a linear magnetic gradient field along the spatial direction and which gradient magnetic field is linear inside a predetermined volume of space permeated by the linear magnetic gradient field.

First claim

The invention claimed is:

1 . A method for producing planar gradient coils for MRI comprises:
defining at least a planar surface along which at least one continuous current wire extends along a path for generating a gradient field along at least one spatial direction of optionally one of three spatial directions defined by a reference cartesian coordinate system; defining the path of the at least one continuous current wire as a spiral path of a single continuous wire filament; describing the spiral path of the at least one continuous current wire by a parametric curve according to a modified version of a Pascal Limaçons curve combined with an Archimede's spiral; applying the Biot-Savart law to evaluate the gradient field generated by the continuous current wire extending along the spiral path; and optimizing parameters of the parametric curve to shape the spiral path of the continuous current wire in such a way as to generate a linear magnetic gradient field along the at least one spatial direction, and which gradient magnetic field is linear inside a predetermined volume of space permeated by the linear magnetic gradient field.

2 . The method according to claim 1 in which an optimization algorithm for optimizing the parameters of the parametric curve defining the spiral path along which the continuous current wire extends is a cost function for minimizing two electrical properties of the gradient coil formed by the continuous wire extending along the spiral path which electrical properties consist in the electrical conductance and the electrical resistance of the coil i.e. of the continuous current wire extending along the spiral path.

3 . The method according to claim 2 , wherein a cost function f of the optimization algorithm is a constrained non-linear programming solver according to the following equation:

min
⁢

f
⁢

such
⁢

that

=

{

max
⁢

❘
"\[LeftBracketingBar]"

B
-

B
target

B
target

❘
"\[RightBracketingBar]"

⁢
%

<
Δ

min
⁢

distance
⁢

between
⁢

path

>
δ

max
⁢

dimensions
⁢

of
⁢

the
⁢

coils

<
Ω

in which Δ is a value of accepted linearity in the gradient coil design, δ is the minimal distance between paths of the windings of the spiral coil that ensure no nodes generation (topological constraint) and Ω is the maximum dimension of the coil in the planar plane where the wire is uncoiled; and
in which B target is the gradient field to be generated and approximated.

4 . The method according to claim 3 in which the optimization step comprises applying a large-scale interior-point algorithm as a constrained non-linear programming solver.

5 . The method according to claim 1 , wherein the method provides for the design of two or more magnetic gradient fields, optionally three magnetic gradient fields, each one being a magnetic gradient field along a different spatial direction of two or more spatial directions, optionally of three spatial directions.

6 . The method according to claim 1 , wherein the three spatial directions are perpendicular one to the other and in a particular embodiment the three spatial directions are defined by the directions of the axis of a three-dimensional cartesian reference system.

7 . The method according to claim 1 , wherein said method steps are carried out separately for producing planar gradient coils for MRI systems, each one of the planar gradient coils generating a magnetic gradient field in only one of the three spatial directions and each one of the gradient coils comprises at least one continuous current wire extending along a spiral path and which is designed according to the steps of the method according to claim 1 .

8 . The method according to claim 7 , wherein each spiral path of the at least one continuous current wire of each one of the three magnetic gradient coils extends along or is contained in the same planar surface.

9 . The method according to claim 1 , wherein the following steps are preliminary steps to be carried out before applying the steps according to claim 1 :
defining a volume of space, so called ROI (Region of Interest); said volume of space being defined by an ideal closed surface enclosing the volume of space and defining the peripheral limits of the volume of space; defining two planar surfaces at diametrically opposite sides of the volume of space along each one of the surfaces the current wire paths of the gradient coils are destined to extends; the two planes being optionally parallel one to the other; defining a three dimensional cartesian coordinate system, the two planes being at a distance along a first axis (y) of the three-dimensional coordinate system and extending parallel to the plane defined by a second and a third axis (x, z) of the coordinate system, the parametric curve describing the spiral wire paths for generating a gradient field in the direction of the third axis (z) is calculated according to the following equation:

l
→︀

=

(

Assignees

• Esaote Spa

Inventors

• Punzo Vincenzo

Classifications

• G01R33/5608

  Data processing and visualization specially adapted for MR, e.g. for feature analysis and pattern recognition on the basis of measured MR data, segmentation of measured MR data, edge contour detection on the basis of measured MR data, for enhancing measured MR data in terms of signal-to-noise ratio by means of noise filtering or apodization, for enhancing measured MR data in terms of resolution by means for deblurring, windowing, zero filling, or generation of gray-scaled images, colour-coded images or images displaying vectors instead of pixels (image data processing or generation, in general G06T) · CPC title

• G01R33/385

  using gradient magnetic field coils · CPC title

• G01R33/34007

  Manufacture of RF coils, e.g. using printed circuit board technology; additional hardware for providing mechanical support to the RF coil assembly or to part thereof, e.g. a support for moving the coil assembly relative to the remainder of the MR system · CPC title

• G01R33/341 Primary

  comprising surface coils · CPC title

• G01R33/3858 Primary

  Manufacture and installation of gradient coils, means for providing mechanical support to parts of the gradient-coil assembly (manufacture of inductances or coils in general H01F41/00) · CPC title