Magnetic resonance coils for simultaneous imaging and B0 shimming

Patent metadata

Field	Value
Publication number	US-11415649-B2
Application number	US-201816650227-A
Country	US
Kind code	B2
Filing date	Sep 28, 2018
Priority date	Sep 28, 2017
Publication date	Aug 16, 2022
Grant date	Aug 16, 2022

Abstract

A coil assembly for MR imaging includes an RF coil element and a shim coil array with a shim coil element. The shim coil element is physically separated from the RF coil element. The shim coil element includes a DC current loop having a DC power supply connection to allow DC current to generate a local B0 magnetic field. The coil assembly simultaneously provides an RF mode for at least one of transmit or receive and a direct current mode to generate a local B0 magnetic field for at least one of B0 shimming an imaging space, MRI spatial encoding of tissue spins, or MRI temporal encoding of tissue spins. The mutual inductance between the shim coil element and the RF coil element is minimized by configuration of blocking elements in the shim coil in order to minimize the RF interaction there between.

First claim

What is claimed is:

1. A Magnetic Resonance Imaging (MRI) system, comprising:
a coil array system including:
an RF coil element operative in an RF mode for at least one of transmit or receive; and
a separate shim coil array having one or more shim coil elements operative in a direct current (DC) mode with DC current flow in the shim coil elements generating local B0 magnetic fields for at least one of B0 shimming, MRI spatial encoding, or MRI temporal encoding;
wherein at least part of the RF coil element and separate shim coil array overlap each other, and wherein the separate shim coil array includes at least one RF blocking element for decoupling the separate shim coil array from the RF coil element;

a magnet bore of a MRI scanner holding a target object, the RF coil element and separate shim coil array positioned about the target object;
a DC power supply in communication with the shim coil array to supply DC current to the shim coil elements of the shim coil array;
a shim coil circuit in communication with the shim coil array configured to direct the DC power supply to supply the DC current to the shim coil elements; and
an RF circuit in communication with the RF coil element configured to receive an MR signal from the object for RF receive or transmit RF pulses to the object for RF transmit.

2. The system of claim 1 , wherein the RF coil element is one of a plurality of RF coil elements in an RF coil array, and wherein N of the shim coil elements are associated with one of the plurality of RF coil elements in the RF coil array, the RF coil array being a receive-only RF coil array, a transmit-only RF coil array, or a transmit/receive RF coil array.

3. The system of claim 2 , wherein the separate shim coil array comprises at least one pair of DC wires, and wherein at least one of the pair of DC wires includes an RF blocking element.

4. The system of claim 3 , wherein the RF blocking element in the at least one of the pair of DC wires is configured to pass at least one of direct current or a current with a frequency of 1 MHz or less.

5. The system of claim 3 , further comprising at least one capacitor coupling the at least one of the pair of DC wires, the at least one capacitor having a capacitance of less than 100 pF.

6. The system of claim 1 , wherein the RF blocking element comprises a circuit having a resonant frequency that is between about 85% of a Larmor frequency of the MRI system and about 115% of the Larmor frequency of the MRI system.

7. The system of claim 6 , wherein the circuit comprises at least one of an inductor and a capacitor.

8. The system of claim 6 , wherein the circuit comprises an inductor with an inductance greater than 100 nH.

9. The system of claim 1 , wherein at least one of the shim coil elements a multiple-turn loop.

10. The system of claim 2 , wherein one of the respective N shim coil elements comprises a detuning trap configured to cause a frequency response of the shim loop to be split around the Larmor frequency of the MR system.

11. The system of claim 2 , wherein at least two of the N shim coil elements are sequentially connected though a pair of DC blocking capacitors.

12. The system of claim 2 , wherein the DC power source includes N channel circuits controlled by the shim circuit, each of the N channel circuits corresponding to one of the N shim coil elements, and wherein the shim circuit allows individual adjustment of a DC current in each of the N shim coil elements.

13. The system of claim 1 , wherein the shape of the shim coil element, the RF coil element, or both, is one of a closed curve, a polygon, a circular shape, a square shape, a rectangular shape, a diamond shape, or a triangular shape.

14. The system of claim 2 , wherein the coil array system includes a plurality of closely stacked layers of individually operable discrete RF coil elements of the RF coil array and the separate shim coil array.

15. The system of claim 1 , wherein a distance between the RF coil element and the separate shim coil array is approximately zero such that least a portion of the RF coil element and at least a portion of the separate shim coil array are physically touching.

16. The system of claim 1 , wherein the distance between the RF coil element and the separate shim coil array is between about 0 millimeters and about 10 millimeters.

17. The system of claim 1 , wherein the RF coil element and the separate shim coil array are positioned in an identical mechanical holding structure of the system.

18. The system of claim 1 , wherein the RF coil element is decoupled from the separate shim coil array such that a mutual inductance between the separate shim coil array and the RF coil element is minimized.

19. The system of claim 1 , wherein a size of one or more shim loop elements in the separate shim coil array are matched to a size of a target anatomical structure of the target object, the target anatomical structure having an inhomogeneous field, and being a prefrontal cortex, a temporal lobe, a spinal cord, a metallic implant within the target object, a heart, a breast, an abdominal region, or any other fine anatomical structure in the target object.

20. The system of claim 19 , wherein the separate shim coil array includes one or more shim coil elements, and wherein a distance between each of the one or more shim coil elements and the target anatomical structure of the target object is minimized.

21. The system of claim 1 , wherein the at least one RF blocking element includes an inductor with an inductance of at least 800 nH.

22. The system of claim 1 , wherein the one or more shim coil elements includes a first set of one or more shim coil elements and a second set of one or more shim coil elements that is sequentially connected to the first set of one or more shim coil elements though a pair of DC blocking capacitors, the second set of one or more shim coil elements being positioned concentrically inside of the first set of one or more shim coil elements.

23. The system of claim 22 , wherein the first set of one or more shim coil elements includes a first circular shim coil element having one or more turns, and wherein the second set of one or more shim coil elements includes a second circular shim coil element having one or more turns, the second circular shim coil element being positioned concentrically inside of the first circular shim coil element.

24. The system of claim 22 wherein the first set of one or more shim coil elements includes a first rectangular shim coil element having one or more turns, and wherein the second set of one or more shim coil elements includes a second rectangular shim coil element having one or more turns, the second rectangular shim coil element being positioned concentrically inside of the first rectangular shim coil element.

25. The system of claim 1 , wherein the shim coil array includes a transformer decouple capacitor formed in-line with the at least one shim coil element, the transformer decouple capacitor being configured to generate a high impedance in the shim coil array at a Larmor frequency of the MRI system.

26. The system of claim 1 , wherein the one or more shim coil elements of the shim coil array are arranged in geometrical asymmetry relative to the RF coil element.

27. The system of claim 1 , wherein the one or more shim coil elements includes a single shim coil element.

28. The s

Assignees

• Cedars Sinai Medical Center

Inventors

• Han Hui
• Li Debiao

Classifications

• G01R33/3635

  Multi-frequency operation · CPC title

• G01R33/3875 Primary

  using correction coil assemblies, e.g. active shimming · CPC title

• G01R33/3815

  with superconducting coils, e.g. power supply therefor · CPC title

• A61B5/055

  involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging · CPC title

• G01R33/3808

  Magnet assemblies for single-sided MR wherein the magnet assembly is located on one side of a subject only; Magnet assemblies for inside-out MR, e.g. for MR in a borehole or in a blood vessel, or magnet assemblies for fringe-field MR · CPC title