# US 2021/0333342 A1 · Dynamic b0 shimming for improved fat saturation in magnetic resonance imaging (mri) > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0333342 A1 - Document ID: US20210333342A1 - Status: Published application - Kind: A1 - Application number: 17/369,924 - Filed: 2021-07-07 - Published: 2021-10-28 - Earliest claimed: 2020-01-07 - Assignees: Synaptive Medical Inc. - Applicants: Synaptive Medical Inc. - Inventors: Philip J. Beatty; Chad Tyler Harris; Curtis Nathan Wiens - Web page: https://patentgrep.com/patent/US20210333342A1 ## CPC - G01R 33/3875: using correction coil assemblies, e.g. active shimming - G01R 33/5607: {by reducing the NMR signal of a particular spin species, e.g. of a chemical species for fat suppression, or of a moving spin species for black-blood imaging} - G01R 33/4828: {Resolving the MR signals of different chemical species, e.g. water-fat imaging} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract A fat saturation method for a magnetic resonance imaging system having a main magnet providing a magnetic field B0 The method includes: driving a shim coil assembly with a first set of shimming currents to sufficiently alter a B0 field inhomogeneity of the magnetic field B0 within a region that includes a first imaging volume of interest such that water saturation inside the region is reduced from before the first set of shimming currents are applied; applying a fat saturation pulse to the region; identifying the first imaging volume of interest from the region; driving the shim coil assembly with a second set of shimming currents to alter the B0 field inhomogeneity of the magnetic field B0 within the first imaging volume of interest such that the B0 field inhomogeneity within the first imaging volume of interest is reduced; and obtaining magnetic resonance signals from the first imaging volume of interest. ## Claims ### Claim 1 A method to perform fat saturation on a magnetic resonance imaging (MRI) system having a main magnet providing a magnetic field B0, the method comprising: driving a shim coil assembly of the MRI system with a first set of shimming currents to sufficiently alter a B0 field inhomogeneity of the magnetic field B0 within a region that includes a first imaging volume of interest such that the B0 field inhomogeneity with respect to a first species of protons within the region is substantially minimized; applying a preparation pulse to the region such that magnetic resonance (MR) signals corresponding to a second species of protons in the region are substantially suppressed; in response to selecting the first imaging volume, driving the shim coil assembly of the MRI system with a second set of shimming currents to sufficiently alter the B0 field inhomogeneity of the magnetic field B0 within the first imaging volume of interest such that the B0 field inhomogeneity with respect to the first species of protons within the first imaging volume of interest is substantially reduced from before applying the second set of shimming currents; and obtaining, using an imaging pulse sequence, the magnetic resonance (MR) signals that encode the first species of protons from the first imaging volume of interest. ### Claim 2 (depends on 1) The method of claim 1, wherein the first species of protons correspond to water protons and the second species of protons correspond to fat protons. ### Claim 3 (depends on 1) The method of claim 1, wherein obtaining magnetic resonance signals from the first imaging volume of interest comprises: applying gradient pulses to encode the MR signals from the first imaging volume of interest; and in response to the gradient pulses, acquiring the MR signals from the first imaging volume of interest. ### Claim 4 (depends on 1) The method of claim 1, wherein the imaging pulse sequence comprises at least one of: a gradient-echo pulse sequence, a spin-echo pulse sequence, a steady-state free precession (SSFP) pulse sequence, and an echo-planar imaging (EPI) pulse sequence. ### Claim 5 (depends on 1) The method of claim 1, wherein driving the shim coil assembly of the MRI system with a first set of shimming currents comprises: driving the shim coil assembly of the MRI system with a first set of shimming currents to substantially minimize water saturation within the region. ### Claim 6 (depends on 1) The method of claim 1, further comprising: selecting a second imaging volume of interest from the region; subsequently driving the shim coil assembly of the MRI system with a third set of shimming currents to alter the B0 field inhomogeneity of the magnetic field B0 within the second imaging volume of interest such that the B0 field inhomogeneity with respect to the first species of protons within the second imaging volume of interest is substantially reduced from before applying the third set of shimming currents; and obtaining, using the imaging pulse sequence, magnetic resonance signals from the second imaging volume of interest. ### Claim 7 (depends on 1) The method of claim 1, further comprising: placing a subject in the main magnet such that the region covers a portion of the subject. ### Claim 8 (depends on 7) The method of claim 7, wherein the portion of the subject includes at least one of: an abdominal organ of the subject, a breast of the subject, a neck of the subject, an extremity of the subject, and a head of the subject. ### Claim 9 (depends on 1) The method of claim 1, wherein prior to obtaining the MR signals from the first imaging volume of interest: applying a first slice-select gradient while applying a first radio-frequency (RF) pulse such that the first species of protons from the first imaging volume of interest are excited by the first RF pulse. ### Claim 10 A magnetic resonance imaging (MRI) system, comprising: a main magnet providing a magnetic field B0; a shim coil assembly; a gradient coil assembly; a radio-frequency (RF) coil; a controller in communication with the shim coil assembly, the gradient coil assembly, and the RF coil, the controller configured to perform operations of: driving a shim coil assembly of the MRI system with a first set of shimming currents to sufficiently alter a B0 field inhomogeneity of the magnetic field B0 within a region that includes a first imaging volume of interest such that the B0 field inhomogeneity with respect to a first species of protons within the region is substantially minimized; applying a preparation pulse to the region such that magnetic resonance (MR) signals corresponding to a second species of protons in the region are substantially suppressed; in response to selecting the first imaging volume, driving the shim coil assembly of the MRI system with a second set of shimming currents to sufficiently alter the B0 field inhomogeneity of the magnetic field B0 within the first imaging volume of interest such that the B0 field inhomogeneity with respect to the first species of protons within the first imaging volume of interest is substantially reduced from before applying the second set of shimming currents; and obtaining, using an imaging pulse sequence, the magnetic resonance (MR) signals encoding the first species of protons from the first imaging volume of interest. ### Claim 11 (depends on 10) The MRI system of claim 10, wherein the first species of protons correspond to water protons and the second species of protons correspond to fat protons. ### Claim 12 (depends on 10) The MRI system of claim 10, wherein obtaining magnetic resonance signals from the first imaging volume of interest comprises: applying gradient pulses to encode the MR signals from the first imaging volume of interest; and in response to the gradient pulses, acquiring the MR signals from the first imaging volume of interest. ### Claim 13 (depends on 10) The MRI system of claim 10, wherein the imaging pulse sequence comprises at least one of: a gradient-echo pulse sequence, a spin-echo pulse sequence, a steady-state free precession (SSFP) pulse sequence, and an echo-planar imaging (EPI) pulse sequence. ### Claim 14 (depends on 10) The MRI system of claim 10, wherein driving the shim coil assembly of the MRI system with a first set of shimming currents comprises: driving the shim coil assembly of the MRI system with a first set of shimming currents to substantially minimize water saturation within the region. ### Claim 15 (depends on 10) The MRI system of claim 10, wherein the operations further comprise: selecting a second imaging volume of interest from the region; subsequently driving the shim coil assembly of the MRI system with a third set of shimming currents to alter the B0 field inhomogeneity of the magnetic field B0 within the second imaging volume of interest such that the B0 field inhomogeneity with respect to the first species of protons within the second imaging volume of interest is substantially reduced from before applying the third set of shimming currents; and obtaining, using the imaging pulse sequence, magnetic resonance signals from the second imaging volume of interest. ### Claim 16 (depends on 10) The MRI system of claim 10, wherein the region covers a portion of a subject placed in the main magnet. ### Claim 17 (depends on 16) The MRI system of claim 16, wherein the portion of the subject includes at least one of: an abdominal organ of the subject, a breast of the subject, a neck of the subject, an extremity of the subject, and a head of the subject. ### Claim 18 (depends on 10) The MRI system of claim 10, wherein prior to obtaining the MR signals from the first imaging volume of interest: applying a first slice-select gradient while applying a first radio-frequency (RF) pulse such that the first species of protons from the first imaging volume of interest are excited by the first RF pulse. ### Claim 19 A method to compute sets of shimming currents for a magnetic resonance imaging (MRI) system having a main magnet that provides a magnetic field B0, the method comprising: obtaining a field map of a portion of the magnetic field B0; based on the field map, computing values of a first set of shimming currents that substantially minimize saturation of a first species of protons within a region that covers a portion of a subject placed in the main magnet; obtaining location information of a first imaging volume of interest, the first imaging volume of interest included by the region; and based on the field map, and the location information of the first imaging volume of interest, computing values of a second set of shimming currents that substantially minimize magnetic field inhomogeneity within the first imaging volume of interest with respect to the first species of protons. ### Claim 20 (depends on 19) The method of claim 19, further comprising: obtaining a map of a second species of protons of the portion of the subject placed in the main magnet; and obtaining a map of the first species of protons of the portion of the subject placed in the main magnet, wherein the first set of shimming currents substantially maximize a saturation of a second species of protons within the region that covers the portion of the subject.