US 11,789,101 B2
Magnetic resonance imaging apparatus and method of compensating for error magnetic field
Naoya Sakaguchi, Tokyo (JP); Syouichi Miyawaki, Tokyo (JP); and Hirokazu Honma, Tokyo (JP)
Assigned to FUJIFILM HEALTHCARE CORPORATION, Chiba (JP)
Filed by HITACHI, LTD., Tokyo (JP)
Filed on Feb. 7, 2020, as Appl. No. 16/784,354.
Claims priority of application No. 2019-080182 (JP), filed on Apr. 19, 2019.
Prior Publication US 2020/0333411 A1, Oct. 22, 2020
Int. Cl. G01R 33/3875 (2006.01); G01R 33/54 (2006.01); G01R 33/385 (2006.01); G01R 33/565 (2006.01)
CPC G01R 33/3875 (2013.01) [G01R 33/3852 (2013.01); G01R 33/543 (2013.01); G01R 33/56518 (2013.01); G01R 33/56563 (2013.01)] 12 Claims
OG exemplary drawing
 
1. A magnetic resonance imaging apparatus, comprising:
a static magnetic field magnet that generates a static magnetic field;
a transmitter/receiver that irradiates a high frequency magnetic field on a subject that is placed in the static magnetic field, and collects nuclear magnetic resonance signals generated from the subject;
a gradient magnetic field coil that adds a gradient magnetic field to the static magnetic field;
a correction coil that corrects non-uniformity of the static magnetic field;
a measurement control unit that controls the transmitter/receiver, the gradient magnetic field coil, and the correction coil; and
a compensation parameter calculation unit that performs calculations related to imaging, wherein
the compensation parameter calculation unit includes a primary compensation parameter calculation unit that calculates primary compensation parameters for a primary error magnetic field, and a secondary compensation parameter calculation unit that calculates secondary compensation parameters for a secondary error magnetic field, wherein
the primary compensation parameter calculation unit uses measurement values of the primary error magnetic field as the primary compensation parameters, generated as a result of applying a test gradient magnetic field of one or a plurality of axes, accompanying with a primary correction magnetic field output for the primary error magnetic field of a gradient magnetic field pulse of each axis, and wherein
the secondary compensation parameter calculation unit calculates, as the secondary compensation parameters, transfer functions whereby an output waveform obtained by applying transfer functions to a step response waveform of the test gradient magnetic field on which the primary correction magnetic field output for the primary error magnetic field is superimposed, best matches measurement values of the secondary error magnetic field; and
the measurement control unit includes a primary correction magnetic field output calculation unit that uses the primary compensation parameters for the primary error magnetic field to calculate the primary correction magnetic field output and a secondary correction magnetic field output calculation unit that uses the secondary compensation parameters for the secondary error magnetic field to calculate a secondary correction magnetic field output; wherein
both the primary correction magnetic field output and the secondary correction magnetic field output are superimposed to be sent as feedback to the primary correction magnetic field output calculation unit, and a last superimposed output after the feedback is supplied as a gradient magnetic field output to the gradient magnetic field coil; and
both the primary correction magnetic field output and the secondary correction magnetic field output, without feedbacking to the primary correction magnetic field output calculation unit, are superimposed as a correction coil output to be supplied to the correction coil.