Techniques for magnetic particle imaging

Patent metadata

Field	Value
Publication number	US-11054392-B2
Application number	US-201816040801-A
Country	US
Kind code	B2
Filing date	Jul 20, 2018
Priority date	Jun 23, 2008
Publication date	Jul 6, 2021
Grant date	Jul 6, 2021

Abstract

A magnetic particle imaging apparatus includes magnets [106,107] that produce a gradient magnetic field having a field free region (FFR), excitation field electromagnets [102,114] that produce a radiofrequency magnetic field within the field free region, high-Q receiving coils [112] that detect a response of magnetic particles in the field free region to the excitation field. Field translation electromagnets create a homogeneous magnetic field displacing the field-free region through the field of view (FOV) allowing the imaging region to be scamled to optimize scan time, scanning power, amplifier heating, SAR, dB/dt, and/or slew rate. Efficient multi-resolution scanning techniques are also provided. Intermodulated low and radio-frequency excitation signals are processed to produce an image of a distribution of the magnetic nanoparticles within the imaging region. A single composite image is computed using deconvolution of multiple signals at different harmonics.

First claim

The invention claimed is:

1. A magnetic particle imaging device, comprising:
a pair of magnets arranged proximate an imaging region of the magnetic particle imaging device, the pair of magnets being configured to produce a gradient magnetic field within the imaging region of the magnetic particle imaging device such that the gradient magnetic field will have a field-free line (FFL);
an excitation magnet configured to produce an excitation magnetic field that induces a signal from an object under observation that contains magnetic tracer,
a receiver arranged proximate the imaging region, the receiver being configured to receive the signal from the magnetic tracer in the imaging region; and
a signal processor configured to be in communication with the receiver, the signal processor being configured to convert the signal into an image of the magnetic tracer,
wherein the pair of magnets is constructed such that each magnet has a longer dimension substantially parallel to the FFL and a shorter dimension substantially perpendicular to the FFL.

2. The magnetic particle imaging device according to claim 1 , wherein the pair of magnets is a pair of permanent magnets.

3. The magnetic particle imaging device according to claim 1 , wherein the pair of magnets is a pair of electromagnets.

4. The magnetic particle imaging device according to claim 1 , wherein the pair of magnets comprises a permanent magnet and an electromagnet.

5. The magnetic particle imaging device according to claim 1 , wherein the magnets of the pair of magnets is a pair of superconducting magnets.

6. The magnetic particle imaging device according to claim 1 , wherein the magnets of the pair of magnets are placed symmetrically about the imaging region and along an axis wherein the FFL is generated.

7. The magnetic particle imaging device according to claim 1 , wherein the pair of magnets has an axis along which one magnet of the pair of magnets is aligned parallel and the other magnet is aligned anti-parallel, and wherein the FFL is perpendicular to this axis.

8. The magnetic particle imaging device according to claim 1 , further comprising a translating magnet configured to produce a translating magnetic field that translates the position of the FFL.

9. The magnetic particle imaging device according to claim 8 , wherein the translating magnetic field displaces the FFL in a direction perpendicular to the FFL.

10. The magnetic particle imaging device according to claim 1 , wherein movement of the FFL is implemented by mechanical movement of the object under observation relative to the pair of magnets.

11. The magnetic particle imaging device according to claim 8 , wherein movement of the FFL is implemented by a combination of dynamic scanning using the translating magnetic field and mechanical movement of the object under observation relative to the pair of magnets.

12. The magnetic particle imaging device according to claim 1 , further comprising a rotation mechanism configured to mechanically rotate the FFL with respect to the object under observation using mechanical movement.

13. The magnetic particle imaging device according to claim 1 , further comprising:
a translating magnet configured to produce a translating magnetic field that translates the position of the FFL along a predetermined trajectory covering a plane perpendicular to the FFL; and
a rotation mechanism configured to mechanically rotate the FFL with respect to the object under observation to change an angle of the FFL with respect to the object under observation.

14. The magnetic particle imaging device according to claim 13 , wherein the receiver is configured to receive a signal from the magnetic tracer in the object under observation at each position of the FFL as the FFL is being displaced, at a plurality of angles of the FFL with respect to the object under observation; and
wherein the signal processor is configured to convert the signals into a 3D image using computed tomographic techniques.

15. A method of magnetic particle imaging, comprising:
placing magnetic particles into an imaging region;
using a pair of magnets to generate within the imaging region an inhomogeneous magnetic field having a spatial gradient and having a field-free line (FFL) within the imaging region;
generating an excitation magnetic field that excites the magnetic particles;
detecting signals produced by the magnetic particles in the imaging region, wherein the signals detected at a given time are produced by magnetic particles located coincident or near to a position of the FFL at the given time; and
producing from the detected signals an image of the magnetic particles in the imaging region,
wherein the pair of magnets is constructed such that each magnet has a longer dimension substantially parallel to the FFL and a shorter dimension substantially perpendicular to the FFL.

16. The method of claim 15 , wherein placing the magnetic particles into the imaging region comprises placing an object into the imaging region, wherein the object contains the magnetic particles.

17. The method of claim 15 , further comprising mechanically rotating the pair of magnets with respect to the magnetic particles in the imaging region.

18. The method of claim 15 , wherein the generating the excitation magnetic field comprises generating a radio-frequency excitation magnetic field in superposition with the inhomogeneous magnetic field generated by the pair of magnets.

19. The method of claim 15 , further comprising generating within the imaging region a scanning magnetic field that displaces the position of the FFL.

20. The method of claim 19 , further comprising rotating, with respect to the magnetic particles in the imaging region, the pair of magnets and magnets used to generate the scanning magnetic field.

21. The method of claim 19 , further comprising displacing the FFL in a direction perpendicular to the FFL using the scanning magnetic field.

22. The method of claim 15 , further comprising displacing the FFL by mechanically moving the magnetic particles in the imaging region relative to the pair of magnets.

23. The method of claim 15 , further comprising displacing the FFL using a scanning magnetic field in combination with mechanical movement of the magnetic particles in the imaging region relative to the pair of magnets.

24. The method of claim 21 , further comprising detecting a first plurality of signals as the FFL is displaced in the direction perpendicular to the FFL;
mechanically rotating the pair of magnets with respect to the magnetic particles placed into the imaging region to change an angle of the FFL with respect to the magnetic particles placed into the imaging region; and
detecting a second plurality of signals as the FFL is displaced in the direction perpendicular to the FFL.

25. The method of claim 15 , comprising:
detecting a plurality of signals at each of a plurality of angles of the pair of magnets with respect to the magnetic particles in the imaging region; and
reconstructing from the plurality of detected signals a 3D image using computed tomographic techniques.

26. The method of claim 16 , wherein the object is at least a portion of an organism.

Assignees

• Univ California

Inventors

• Goodwill Patrick W
• Conolly Steven M

Classifications

• A61B5/05 Primary

  Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves (measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24) · CPC title

• A61B5/0515

  Magnetic particle imaging · CPC title

• G01R33/00

  Arrangements or instruments for measuring magnetic variables · CPC title

• G01R33/10

  Plotting field distribution {; Measuring field distribution} · CPC title

• G01N27/72 Primary

  by investigating magnetic variables · CPC title