Magnetic particle imaging (MPI) device based on asymmetric bilateral structure

Patent metadata

Field	Value
Publication number	US-12265142-B1
Application number	US-202418922363-A
Country	US
Kind code	B1
Filing date	Oct 21, 2024
Priority date	Mar 7, 2024
Publication date	Apr 1, 2025
Grant date	Apr 1, 2025

Abstract

A magnetic particle imaging (MPI) device based on an asymmetric bilateral structure includes a fixed section and a movable section. The fixed section includes a pair of magnetic field generation coils, and the magnetic field generation coils are configured to generate a uniform and variable magnetic field and drive a field-free point (FFP) to move along a Z-axis direction. The movable section includes a permanent magnet, excitation coils and a reception coil. The permanent magnet is configured to cooperate with the magnetic field generation coils to generate the FFP. The excitation coils are configured to move the FFP on a two-dimensional plane and excite magnetic particles to generate a nonlinear response signal. The reception coil is configured to receive an MPI signal. The MPI device is simple in structure and convenient to operate, and can perform targeted local imaging or covered overall imaging on the target object.

First claim

The invention claimed is:

1. A magnetic particle imaging (MPI) device based on an asymmetric bilateral structure, comprising a fixed section and a movable section;
the fixed section comprises a pair of magnetic field generation coils, and the magnetic field generation coils are configured to generate a uniform and variable magnetic field and drive the field-free point (FFP) to move along a Z-axis direction;
the movable section comprises a permanent magnet, excitation coils and a reception coil;
the permanent magnet is configured to cooperate with the magnetic field generation coils to generate the FFP; the excitation coils are configured to move the FFP on a two-dimensional plane and excite magnetic particles to generate a nonlinear response signal; the reception coil is configured to receive an MPI signal;
the Z-axis direction is an axial direction of the permanent magnet, and the two-dimensional plane is perpendicular to the Z-axis direction;
the magnetic field generation coils comprise a first magnetic field generation coil and a second magnetic field generation coil; and
the first magnetic field generation coil and the second magnetic field generation coil are symmetrically arranged at a center of an imaging field of view; direct currents of an equal magnitude and a same direction are introduced into the first magnetic field generation coil and the second magnetic field generation coil, and the first magnetic field generation coil and the second magnetic field generation coil cooperate with the permanent magnet to generate the FFP between the first magnetic field generation coil and the second magnetic field generation coil.

2. The MPI device based on the asymmetric bilateral structure according to claim 1 , wherein the shape of the permanent magnet comprises a cylindrical shape, and the excitation coils are uniformly arranged around an outer circumferential surface of the permanent magnet;
the excitation coils comprise a first pair of excitation coils and a second pair of excitation coils, and alternating currents of an equal magnitude and opposite directions are respectively introduced into two excitation coils in a same pair;
the first pair of excitation coils comprises a first excitation coil and a second excitation coil;
the first excitation coil and the second excitation coil are centrosymmetric along an axis of the permanent magnet;
the second pair of excitation coils comprises a third excitation coil and a fourth excitation coil; and
the third excitation coil and the fourth excitation coil are centrosymmetric along the axis of the permanent magnet.

3. The MPI device based on the asymmetric bilateral structure according to claim 2 , wherein a connection line between a center of the first excitation coil and a center of the second excitation coil in a first same end face is taken as a first connection line;
a connection line between a center of the third excitation coil and a center of the fourth excitation coil in a second same end face is taken as a second connection line; and
the first connection line is perpendicular to the second connection line.

4. The MPI device based on the asymmetric bilateral structure according to claim 3 , wherein the reception coil is arranged at a bottom of the excitation coils.

5. The MPI device based on the asymmetric bilateral structure according to claim 4 , wherein a size of an imaging range is changed by changing a distance between the first magnetic field generation coil and the second magnetic field generation coil or current magnitudes.

6. The MPI device based on the asymmetric bilateral structure according to claim 4 , wherein both the first magnetic field generation coil and the second magnetic field generation coil comprise Helmholtz coils.

7. The MPI device based on the asymmetric bilateral structure according to claim 6 , wherein a use method of the MPI device comprises:
placing a target object injected with magnetic nanoparticles at a center position of the uniform and variable magnetic field between the first magnetic field generation coil and the second magnetic field generation coil, and introducing direct currents of an equal magnitude and a same direction, wherein at this time, the FFP is generated under an action of a magnetic field of the permanent magnet;
respectively introducing alternating currents of an equal magnitude and opposite directions into two excitation coils in the first pair of excitation coils as well as the second pair of excitation coils for moving the FFP to achieve two-dimensional planar scanning at a fixed height, exciting the MPI signal when the FFP is driven to move, and receiving the MPI signal by the reception coil and performing reconstruction to obtain an MPI two-dimensional image;
superimposing low-frequency and high-amplitude alternating currents on the first magnetic field generation coil and the second magnetic field generation coil to move the FFP in the Z-axis direction and perform two-dimensional planar scanning on layers at different heights, receiving the MPI signal of each layer by the reception coil, and at the same time, decoding, by a computer, the MPI signal and reconstructing an MPI three-dimensional image using an MPI imaging algorithm; and
according to a size of the target object and an imaged region, determining whether it is necessary to move the movable section for real-time imaging in a larger range until imaging requirements of the target object are met.

8. The MPI device based on the asymmetric bilateral structure according to claim 7 , wherein the MPI imaging algorithm comprises a systematic matrix imaging method or an X-space imaging method.

9. The MPI device based on the asymmetric bilateral structure according to claim 8 , wherein the alternating currents of the equal magnitude and opposite directions are respectively introduced into the two excitation coils in the first pair of excitation coils as well as the second pair of excitation coils as follows:
a current I 1 introduced into the first excitation coil is:
I 1 =Ix ×cos(2× pi×fx×t );

a current I 2 introduced into the second excitation coil is:
I 2 =−Ix ×cos(2× pi×fx×t );

a current I 3 introduced into the third excitation coil is:
I 3 =Iy ×cos(2× pi×fy×t );

a current I 4 introduced into the fourth excitation coil is:
I 4 =−Iy ×cos(2× pi×fy×t );

wherein Ix is an amplitude of the current I 1 introduced into the first excitation coil and the current I 2 introduced into the second excitation coil; fx is a frequency of the current I 1 introduced into the first excitation coil and the current I 2 introduced into the second excitation coil; Iy is an amplitude of the current I 3 introduced into the third excitation coil and the current I 4 introduced into the fourth excitation coil; fy is a frequency of the current I 3 introduced into the third excitation coil and the current I 4 introduced into the fourth excitation coil; pi is π; and t is a time variable of a current function with time.

Assignees

• Univ Beihang

Inventors

• Tian Jie
• Tang Zhenchao
• Zhou Guangxing
• An Yu

Classifications

• G01R33/1276 Primary

  of magnetic particles, e.g. imaging of magnetic nanoparticles (G01R33/1269 takes precedence) · CPC title

• A61B5/0515

  Magnetic particle imaging · CPC title

• G01R33/0005

  Geometrical arrangement of magnetic sensor elements; Apparatus combining different magnetic sensor types (G01R33/0206 takes precedence) · CPC title

• G01R33/0011

  comprising means, e.g. flux concentrators, flux guides, for guiding or concentrating the magnetic flux, e.g. to the magnetic sensor · CPC title