# US 11,307,279 B2 · Magnetic resonance imaging method and apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,307,279 B2 - Document ID: US11307279B2 - Status: Granted - Kind: B2 - Application number: 17/179,853 - Filed: 2021-02-19 - Published: 2021-09-09 - Granted: 2022-04-19 - Earliest claimed: 2020-03-09 - Assignees: Canon Medical Systems Corporation - Applicants: Canon Medical Systems Corporation - Inventors: Hiroki Kondo; Masanori Ozaki; Masaaki Umeda - Web page: https://patentgrep.com/patent/US11307279B2 ## CPC - G01R 33/5617: {using RF refocusing, e.g. RARE} - G01R 33/4818: {MR characterised by data acquisition along a specific k-space trajectory or by the temporal order of k-space coverage, e.g. centric or segmented coverage of k-space} - G01R 33/56509: {due to motion, displacement or flow, e.g. gradient moment nulling (G01R33/567 takes precedence)} - G01R 33/56554: {caused by acquiring plural, differently encoded echo signals after one RF excitation, e.g. correction for readout gradients of alternating polarity in EPI} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract A magnetic resonance imaging method according to an embodiment is a method for implementing a multi-shot Fast Spin Echo method. The method includes acquiring, for a k-space divided into a plurality of segments with respect to a phase encode direction, one of the segments including a central region of the k-space with one shot, wherein, during the one-shot acquisition for the central region of the k-space, refocus pulses corresponding to a first time period among refocus pulses applied a plurality of times have a flip angle decreasing tendency, and refocus pulses corresponding to a second time period following the first time period among the refocus pulses applied the plurality of times have a flip angle maintaining or increasing tendency. ## Claims ### Claim 1 A magnetic resonance imaging method for implementing a multi-shot Fast Spin Echo (FSE) method by which a k-space is filled with data by executing multiple sessions of one-shot acquisition during each of which a refocus pulse is applied a plurality of times after an excitation pulse is applied once, so as to acquire a plurality of echo signals, the magnetic resonance imaging method comprising: acquiring, for the k-space divided into a plurality of segments with respect to a phase encode direction, one of the segments including a central region of the k-space with one shot, wherein, during the one-shot acquisition for the central region of the k-space, refocus pulses corresponding to a first time period among the refocus pulses applied the plurality of times have a flip angle decreasing tendency, and refocus pulses corresponding to a second time period following the first time period among the refocus pulses applied the plurality of times have a flip angle maintaining or increasing tendency. ### Claim 2 (depends on 1) The magnetic resonance imaging method according to claim 1, wherein the plurality of echo signals obtained by the shots in the multiple sessions are arranged in the k-space in such a manner that a segment filled with echo signals so as to have increasing TE (echo time) lengths is positioned contiguous to a segment filled with echo signals so as to have decreasing TE lengths. ### Claim 3 (depends on 1) The magnetic resonance imaging method according to claim 1, further comprising: acquiring, for the k-space divided into the plurality of segments with respect to the phase encode direction, one of the segments including a region other than the central region with one shot, wherein a flip angle tendency of the refocus pulses used in the acquisition for the central region of the k-space is caused to be different from a flip angle tendency of the refocus pulses used in the acquisition for the region other than the central region of the k-space. ### Claim 4 (depends on 1) The magnetic resonance imaging method according to claim 1, wherein during the acquisition for the region other than the central region of the k-space, a flip angle of the refocus pulses corresponding to the first time period and to the second time period is kept unchanged. ### Claim 5 (depends on 1) The magnetic resonance imaging method according to claim 1, wherein echo signals corresponding to the first time period are regarded as a dummy and are not arranged in the k-space, and an MR image is further generated by reconstructing the k-space not including the dummy, on a basis of the plurality of echo signals. ### Claim 6 (depends on 5) The magnetic resonance imaging method according to claim 5, further comprising: acquiring, for the k-space divided into the plurality of segments with respect to the phase encode direction, one of the segments including a region other than the central region of the k-space with one shot, wherein, during the acquisition for the central region of the k-space, the echo signals corresponding to the first time period are regarded as the dummy and are not arranged in the k-space, whereas during the acquisition for the region other than the central region of the k-space, all acquired echo signals are arranged in the k-space. ### Claim 7 (depends on 5) The magnetic resonance imaging method according to claim 5, further comprising: acquiring, for the k-space divided into the plurality of segments with respect to the phase encode direction, one of the segments including a region other than the central region of the k-space with one shot, wherein, during the acquisition for the central region of the k-space, the echo signals corresponding to the first time period are regarded as the dummy and are not arranged in the k-space, whereas during the acquisition for the region other than the central region of the k-space, a quantity of echo signals treated as a dummy is set to be smaller than that for the central region of the k-space. ### Claim 8 (depends on 1) The magnetic resonance imaging method according to claim 1, further comprising: acquiring, for the k-space divided into the plurality of segments with respect to the phase encode direction, one of the segments including a region other than the central region of the k-space with one shot, wherein an acquisition direction, in terms of the phase encode direction, of the one-shot acquisition for the central region of the k-space is caused to be different from an acquisition direction, in terms of the phase encode direction, of the one-shot acquisition for a region positioned adjacent to the central region of the k-space. ### Claim 9 A magnetic resonance imaging apparatus that implements a multi-shot Fast Spin Echo (FSE) method by which a k-space is filled with data by executing multiple sessions of one-shot acquisition during each of which a refocus pulse is applied a plurality of times after an excitation pulse is applied once, so as to acquire a plurality of echo signals, the magnetic resonance imaging apparatus comprising: processing circuitry configured to acquire, for the k-space divided into a plurality of segments with respect to a phase encode direction, one of the segments including a central region of the k-space with one shot, wherein, during the one-shot acquisition for the central region of the k-space, refocus pulses corresponding to a first time period among the refocus pulses applied the plurality of times have a flip angle decreasing tendency, and refocus pulses corresponding to a second time period following the first time period among the refocus pulses applied the plurality of times have a flip angle maintaining or increasing tendency. ### Claim 10 (depends on 9) The magnetic resonance imaging apparatus according to claim 9, wherein the processing circuitry arranges, in the k-space, the plurality of echo signals obtained by the shots in the multiple sessions, in such a manner that a segment filled with echo signals so as to have increasing TE (echo time) lengths is positioned contiguous to a segment filled with echo signals so as to have decreasing TE lengths. ### Claim 11 (depends on 9) The magnetic resonance imaging apparatus according to claim 9, wherein the processing circuitry further acquires, for the k-space divided into the plurality of segments with respect to the phase encode direction, one of the segments including a region other than the central region with one shot, and the processing circuitry causes a flip angle tendency of the refocus pulses used in the acquisition for the central region of the k-space to be different from a flip angle tendency of the refocus pulses used in the acquisition for the region other than the central region of the k-space. ### Claim 12 (depends on 9) The magnetic resonance imaging apparatus according to claim 9, wherein during the acquisition for the region other than the central region of the k-space, the processing circuitry keeps unchanged a flip angle of the refocus pulses corresponding to the first time period and to the second time period. ### Claim 13 (depends on 9) The magnetic resonance imaging apparatus according to claim 9, wherein the processing circuitry regards echo signals corresponding to the first time period as a dummy and does not arrange the echo signals in the k-space, and the processing circuitry further generates an MR image by reconstructing the k-space not including the dummy, on a basis of the plurality of echo signals. ### Claim 14 (depends on 13) The magnetic resonance imaging apparatus according to claim 13, wherein the processing circuitry further acquires, for the k-space divided into the plurality of segments with respect to the phase encode direction, one of the segments including a region other than the central region of the k-space with one shot, during the acquisition for the central region of the k-space, the processing circuitry regards the echo signals corresponding to the first time period as the dummy and does not arrange the echo signals in the k-space, and during the acquisition for the region other than the central region of the k-space, the processing circuitry arranges all acquired echo signals in the k-space. ### Claim 15 (depends on 13) The magnetic resonance imaging apparatus according to claim 13, wherein the processing circuitry further acquires, for the k-space divided into the plurality of segments with respect to the phase encode direction, one of the segments including a region other than the central region of the k-space with one shot, during the acquisition for the central region of the k-space, the processing circuitry regards the echo signals corresponding to the first time period as the dummy and does not arrange the echo signals in the k-space, and, during the acquisition for the region other than the central region of the k-space, the processing circuitry sets a quantity of echo signals treated as a dummy to be smaller than that for the central region of the k-space. ### Claim 16 (depends on 9) The magnetic resonance imaging apparatus according to claim 9, wherein the processing circuitry further acquires, for the k-space divided into the plurality of segments with respect to the phase encode direction, one of the segments including a region other than the central region of the k-space with one shot, and the processing circuitry causes an acquisition direction, in terms of the phase encode direction, of the one-shot acquisition for the central region of the k-space to be different from an acquisition direction, in terms of the phase encode direction, of the one-shot acquisition for a region positioned adjacent to the central region of the k-space.