# US 11,029,377 B2 · Method and system for reducing magnetic field instabilities in a magnetic resonance system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,029,377 B2 - Document ID: US11029377B2 - Status: Granted - Kind: B2 - Application number: 16/558,893 - Filed: 2019-09-03 - Published: 2021-03-04 - Granted: 2021-06-08 - Earliest claimed: 2019-09-03 - Assignees: Synaptive Medical Inc. - Applicants: Ian Connell; Chad Harris; Geron Bindseil; Andrew T. Curtis - Inventors: Ian Connell; Chad Harris; Geron Bindseil; Andrew T. Curtis - Web page: https://patentgrep.com/patent/US11029377B2 ## CPC - G01R 33/3875: using correction coil assemblies, e.g. active shimming - G01R 33/381: using electromagnets - G01R 33/389: Field stabilisation {, e.g. by field measurements and control means or indirectly by current stabilisation} - G01R 33/543: {Control of the operation of the MR system, e.g. setting of acquisition parameters prior to or during MR data acquisition, dynamic shimming, use of one or more scout images for scan plane prescription (G01R33/546 takes precedence)} - G01R 33/56518: {due to eddy currents, e.g. caused by switching of the gradient magnetic field} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract A method, device, and system for reducing inhomogeneity in an imaging magnetic field during magnetic resonance imaging is described. The method includes generating a corrective magnetic field during imaging, the corrective magnetic field having a first magnetic field component and a second magnetic field component with a phase separation therebetween. The first and second components are generated according to a stability parameter decomposed from a stability field that correct an instability identified within the imaging magnetic field. ## Claims ### Claim 1 A method for reducing instability in an imaging magnetic field within an imaging bore of a magnetic resonance imagining (MRI) system during magnetic resonance imaging, the method comprising: identifying an instability within the imaging magnetic field; determining a stability field in response to the instability in the imaging magnetic field, the stability field being a magnetic field that is similar but opposite to that caused by the instability in the imaging magnetic field; decomposing the stability field temporally into Fourier domain and extracting amplitude and phase for each spatial position as stability parameters; creating at least two spatial magnetic field components from the stability parameters with a phase separation therebetween as a first magnetic field component and a second magnetic field component; and generating the first and second magnetic field components as a corrective magnetic field within the imaging bore of the MRI system during imaging to reduce the instability in the imaging magnetic field. ### Claim 2 (depends on 1) The method of claim 1, wherein the first and second magnetic field components are, respectively, an in-phase magnetic field component and an out-of-phase magnetic field component. ### Claim 3 (depends on 2) The method of claim 2, wherein the phase separation is 90 degrees. ### Claim 4 (depends on 1) The method of claim 1, further comprising designing a first electromagnet to generate the first magnetic field component, and designing a second electromagnet to generate the second magnetic field component. ### Claim 5 (depends on 1) The method of claim 1, wherein generating the corrective magnetic field comprises: driving a first electromagnet designed to generate the first magnetic field component of the corrective magnetic field with a first waveform; and driving a second electromagnet designed to generate the second magnetic field component of the corrective magnetic field with a second waveform. ### Claim 6 (depends on 5) The method of claim 5, wherein the first electromagnet is a first shim coil and the second electromagnet is a second shim coil. ### Claim 7 (depends on 5) The method of claim 5, wherein the instability in the imaging magnetic field is constant or sporadic over time. ### Claim 8 (depends on 7) The method of claim 7, wherein the instability is sporadic over time, the method further comprising: detecting a change in the instability in the imaging magnetic field; dynamically changing parameters at which the first and second electromagnets are driven to reduce the instability in the imaging magnetic field due to the change. ### Claim 9 A system for reducing instability in an imaging magnetic field in an imaging bore of a magnetic resonance imaging (MRI) system during imaging, the system comprising: a processor having memory containing instructions to: identify an instability within the imaging magnetic field; determine a stability field in response to the instability in the imaging magnetic field, the stability field being a magnetic field that is similar but opposite to that caused by the instability in the imaging magnetic field; decompose the stability field temporally into Fourier domain and extracting amplitude and phase for each spatial position as stability parameters; and create at least two spatial magnetic field components from the stability parameters with a phase separation therebetween as a first magnetic field component and a second magnetic field component; and an electromagnet assembly coupled to the processor to receive the first and second magnetic field components therefrom, the electromagnet assembly configured to generate the first and second magnetic field components as a corrective magnetic field in the imaging bore of the MRI system to reduce the instability in the imaging magnetic field. ### Claim 10 (depends on 9) The system of claim 9, wherein the first and second magnetic field components are, respectively, an in-phase magnetic field component and an out-of-phase magnetic field component. ### Claim 11 (depends on 10) The system of claim 10, wherein the phase shift is a 90 degree phase shift. ### Claim 12 (depends on 9) The system of claim 9, wherein the electromagnet assembly comprises: a first electromagnet designed to generate the first magnetic field component of the corrective magnetic field with a first waveform; and a second electromagnet designed to generate the second magnetic field component of the corrective magnetic field with a second waveform. ### Claim 13 (depends on 9) The system of claim 9, wherein the first electromagnet is a first shim coil and the second electromagnet is a second shim coil. ### Claim 14 (depends on 13) The system of claim 13, wherein the first and second shim coils are independently driven. ### Claim 15 (depends on 12) The system of claim 12, further comprising: a sensor for detecting a change in the instability in the imaging magnetic field, the sensor operatively coupled to the first and second electromagnets for dynamically changing parameters at which the first and second shim coils are driven to reduce the instability in the imaging magnetic field due to the change.