IP Library › Granted Patent US 12669561
Granted Patent B2
US 12669561 · App. 18/459,712 · Granted Jun 30, 2026

Active shimming for low-field magnetic resonance imaging

Inventors: Rishabh Ostawal (San Francisco, CA); Ghoncheh Amouzandeh (Alameda, CA); Haidong Peng (San Francisco, CA); Hung-Yu Lin (Walnut Creek, CA)
Assignee: neuro42, Inc.
G01R33/383G01R33/385G01R33/3875G01R33/445
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Quick Facts
Patent No.
US 12669561
App. No.
18/459,712
Granted
Jun 30, 2026
Kind
B2
Abstract

The present disclosure provides various devices, systems, and methods for active shimming for an MRI system. For example, an MRI system can a first gradient coil, a second gradient coil, a third gradient coil, and a permanent magnet. The permanent magnet is configured to generate a magnetic field B 0 having a low field strength. A method for active shimming the MRI system can include a set of candidate shimming configurations with first current values associated with the first gradient coil, second current values associated with the second gradient coil, and third current values associated with the third gradient coil. The method further includes applying, for each candidate shimming configuration, a pulse sequence; acquiring, for each pulse sequence, a magnetic resonance (MR) signal; determining, for each MR signal, a signal bandwidth based on a frequency domain of the MR signal; and designating a shimming configuration for the MRI system.

Claims (67)

1 . A method of active shimming for a magnet resonance imaging (MRI) system, the MRI system comprising a first gradient coil, a second gradient coil, a third gradient coil, and a permanent magnet, wherein the permanent magnet is configured to generate a magnetic field B 0 having a low field strength, the method comprising:

selecting a set of candidate shimming configurations, wherein the set of candidate shimming configurations is a first set of candidate shimming configurations, wherein the set of candidate shimming configurations comprises first current values associated with the first gradient coil from a first range of current values, second current values associated with the second gradient coil from a second range of current values, and third current values associated with the third gradient coil from a third range of current values;

applying, for each candidate shimming configuration, a pulse sequence;

acquiring, for each pulse sequence, a magnetic resonance (MR) signal;

determining, for each MR signal, a signal bandwidth based on a frequency domain of the MR signal;

designating a shimming configuration for the MRI system, wherein the shimming configuration is based on the candidate shimming configuration corresponding to the narrowest signal bandwidth of the MR signals for the set of candidate shimming configurations; and

selecting a second set of candidate shimming configurations based on the candidate shimming configuration corresponding to the narrowest signal bandwidth of the MR signals for the first set of candidate shimming configurations.

2 . The method of claim 1 , further comprising:

plotting the signal bandwidths for the set of candidate shimming configurations in a three-dimensional array, wherein the three-dimensional array comprises a first dimension comprising the first current values, a second dimension comprising the second current values, and a third dimension comprising the third current values; and

determining the candidate shimming configuration corresponding to the narrowest signal bandwidth of the MR signals for the set of candidate shimming configurations based on the three-dimensional array.

3 . The method of claim 1 , further comprising:

for each candidate shimming configuration of the second set of candidate shimming configurations, applying the pulse sequence, acquiring the MR signal, and determining the signal bandwidth based on the frequency domain of the MR signal; and

designating the shimming configuration for the MRI system based on the candidate shimming configuration corresponding to the narrowest signal bandwidth of the MR signals for the second set of candidate shimming configurations.

4 . The method of claim 1 , wherein selecting the second set of candidate shimming configurations comprises:

selecting a fourth range of current values, a fifth range of current values, and a sixth range of current values based on the candidate shimming configuration corresponding to the narrowest signal bandwidth of the MR signals for the first set of candidate shimming configurations;

wherein the second set of candidate shimming configurations comprises fourth current values associated with the first gradient coil from the fourth range of current values, fifth current values associated with the second gradient coil from the fifth range of current values, and sixth current values associated with the third gradient coil from the sixth range of current values.

5 . The method of claim 1 , wherein the set of candidate shimming configurations comprises candidate shimming configurations derived based on combining each of the first current values with each of the second current values and each of the third current values.

6 . The method of claim 1 , wherein the MRI system comprises a dome-shaped housing comprising a head coil, and wherein acquiring the MR signal comprises acquiring the MR signal induced in a phantom positioned within the head coil.

7 . The method of claim 1 , further comprising:

setting baseline current values for the first gradient coil, the second gradient coil, and the third gradient coil based on designating the shimming configuration for the MRI system.

8 . The method of claim 1 , wherein the MR system further comprises a radiofrequency (RF) coil, and wherein applying, for each candidate shimming configuration, the pulse sequence comprises:

modifying the magnetic field B 0 in a first manner by applying current to the first gradient coil according to the candidate shimming configuration;

modifying the magnetic field B 0 in a second manner by applying current to the second gradient coil according to the candidate shimming configuration;

modifying the magnetic field B 0 in a third manner by applying current to the third gradient coil according to the candidate shimming configuration; and

generating, by the RF coil, an RF pulse to induce the MR signal.

9 . The method of claim 8 , wherein generating the RF pulse to induce the MR signal comprises generating a spin-echo pulse sequence.

10 . The method of claim 1 , wherein applying, for each candidate shimming configuration, the pulse sequence comprises applying, for each candidate shimming configuration, at least two pulse sequences, and wherein acquiring, for each pulse sequence, the MR signal comprises acquiring at least two MR signals for each candidate shimming configuration, the method further comprising:

determining, for each candidate shimming configuration, an average signal bandwidth based on the at least two MR signals acquired for the candidate shimming configuration.

11 . A method of active shimming for a magnet resonance imaging (MRI) system, the MRI system comprising a first gradient coil, a second gradient coil, a third gradient coil, and a permanent magnet, wherein the permanent magnet is configured to generate a magnetic field B 0 having a low field strength, the method comprising:

selecting a set of candidate shimming configurations, wherein the set of candidate shimming configurations comprises first current values associated with the first gradient coil from a first range of current values, second current values associated with the second gradient coil from a second range of current values, and third current values associated with the third gradient coil from a third range of current values, and wherein the set of candidate shimming configurations comprises candidate shimming configurations derived based on combining each of the first current values with each of the second current values and each of the third current values;

applying, for each candidate shimming configuration, a pulse sequence;

acquiring, for each pulse sequence, a magnetic resonance (MR) signal;

determining, for each MR signal, a signal bandwidth based on a frequency domain of the MR signal; and

designating a shimming configuration for the MRI system, wherein the shimming configuration is based on the candidate shimming configuration corresponding to the narrowest signal bandwidth of the MR signals for the set of candidate shimming configurations.

12 . The method of claim 11 , further comprising:

plotting the signal bandwidths for the set of candidate shimming configurations in a three-dimensional array, wherein the three-dimensional array comprises a first dimension comprising the first current values, a second dimension comprising the second current values, and a third dimension comprising the third current values; and

determining the candidate shimming configuration corresponding to the narrowest signal bandwidth of the MR signals for the set of candidate shimming configurations based on the three-dimensional array.

13 . The method of claim 11 , wherein the MRI system comprises a dome-shaped housing comprising a head coil, and wherein acquiring the MR signal comprises acquiring the MR signal induced in a phantom positioned within the head coil.

14 . The method of claim 11 , further comprising:

setting baseline current values for the first gradient coil, the second gradient coil, and the third gradient coil based on designating the shimming configuration for the MRI system.

15 . The method of claim 11 , wherein the MR system further comprises a radiofrequency (RF) coil, and wherein applying, for each candidate shimming configuration, the pulse sequence comprises:

modifying the magnetic field B 0 in a first manner by applying current to the first gradient coil according to the candidate shimming configuration;

modifying the magnetic field B 0 in a second manner by applying current to the second gradient coil according to the candidate shimming configuration;

modifying the magnetic field B 0 in a third manner by applying current to the third gradient coil according to the candidate shimming configuration; and

generating, by the RF coil, an RF pulse to induce the MR signal.

16 . The method of claim 15 , wherein generating the RF pulse to induce the MR signal comprises generating a spin-echo pulse sequence.

17 . The method of claim 11 , wherein applying, for each candidate shimming configuration, the pulse sequence comprises applying, for each candidate shimming configuration, at least two pulse sequences, and wherein acquiring, for each pulse sequence, the MR signal comprises acquiring at least two MR signals for each candidate shimming configuration, the method further comprising:

determining, for each candidate shimming configuration, an average signal bandwidth based on the at least two MR signals acquired for the candidate shimming configuration.

18 . A method of active shimming for a magnet resonance imaging (MRI) system, the MRI system comprising a first gradient coil, a second gradient coil, a third gradient coil, and a permanent magnet, wherein the permanent magnet is configured to generate a magnetic field B 0 having a low field strength, the method comprising:

selecting a set of candidate shimming configurations, wherein the set of candidate shimming configurations comprises first current values associated with the first gradient coil from a first range of current values, second current values associated with the second gradient coil from a second range of current values, and third current values associated with the third gradient coil from a third range of current values;

applying, for each candidate shimming configuration, at least two pulse sequences;

acquiring, for each pulse sequence, at least two magnetic resonance (MR) signals for each candidate shimming configuration;

determining, for each candidate shimming configuration, an average signal bandwidth based on the at least two MR signals acquired for the candidate shimming configuration;

determining, for each MR signal, a signal bandwidth based on a frequency domain of the MR signal; and

designating a shimming configuration for the MRI system, wherein the shimming configuration is based on the candidate shimming configuration corresponding to the narrowest signal bandwidth of the MR signals for the set of candidate shimming configurations.

19 . The method of claim 18 , further comprising:

plotting the signal bandwidths for the set of candidate shimming configurations in a three-dimensional array, wherein the three-dimensional array comprises a first dimension comprising the first current values, a second dimension comprising the second current values, and a third dimension comprising the third current values; and

determining the candidate shimming configuration corresponding to the narrowest signal bandwidth of the MR signals for the set of candidate shimming configurations based on the three-dimensional array.

20 . The method of claim 18 , wherein the MRI system comprises a dome-shaped housing comprising a head coil, and wherein acquiring the MR signal comprises acquiring the MR signal induced in a phantom positioned within the head coil.

21 . The method of claim 18 , further comprising:

setting baseline current values for the first gradient coil, the second gradient coil, and the third gradient coil based on designating the shimming configuration for the MRI system.

22 . The method of claim 18 , wherein the MR system further comprises a radiofrequency (RF) coil, and wherein applying, for each candidate shimming configuration, the pulse sequence comprises:

modifying the magnetic field B 0 in a first manner by applying current to the first gradient coil according to the candidate shimming configuration;

modifying the magnetic field B 0 in a second manner by applying current to the second gradient coil according to the candidate shimming configuration;

modifying the magnetic field B 0 in a third manner by applying current to the third gradient coil according to the candidate shimming configuration; and

generating, by the RF coil, an RF pulse to induce the MR signal.

23 . The method of claim 22 , wherein generating the RF pulse to induce the MR signal comprises generating a spin-echo pulse sequence.