# US 2021/0333341 A1 · Open-type magnetic resonance imaging apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0333341 A1 - Document ID: US20210333341A1 - Status: Published application - Kind: A1 - Application number: 17/195,796 - Filed: 2021-03-09 - Published: 2021-10-28 - Earliest claimed: 2020-04-27 - Assignees: Hitachi, Ltd. - Applicants: Hitachi, Ltd. - Inventors: Taisuke TAKAYANAGI; Manabu AOKI; Yukinobu IMAMURA; Hiroyuki TAKEUCHI - Web page: https://patentgrep.com/patent/US20210333341A1 ## CPC - G01R 33/3806: {Open magnet assemblies for improved access to the sample, e.g. C-type or U-type magnets} - G01R 33/385: using gradient magnetic field coils - G01R 33/30: Sample handling arrangements, e.g. sample cells, spinning mechanisms - G01R 33/3875: using correction coil assemblies, e.g. active shimming - G01R 33/4215: {of the gradient magnetic field, e.g. using passive or active shielding of the gradient magnetic field} - G01R 33/383: using permanent magnets - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract An open-type MRI apparatus includes a pair of static magnetic field magnets and a pair of gradient magnetic field coils. Each static magnetic field magnet includes a discoid magnetic pole configured to generate a static magnetic field in a Z axis direction in which the pair of static magnetic field magnets are opposed each other, and an annular magnetic pole configured to generate a static magnetic field on an X-Y plane perpendicular to the Z axis direction. Each gradient magnetic field coil includes a Z coil configured to provide a magnetic field being gradient in the Z axis direction in the imaging region, a magnetic material block configured to shield the discoid magnetic pole from a magnetic flux generated from the Z coil, and a correction coil configured to shield the annular magnetic pole from the magnetic flux generated from the Z coil. ## Claims ### Claim 1 An open-type magnetic resonance imaging apparatus comprising: a pair of static magnetic field magnets opposed to each other with respect to an imaging region; and a pair of gradient magnetic field coils opposed to each other with respect to the imaging region, wherein each static magnetic field magnet includes a discoid magnetic pole configured to generate a static magnetic field in a Z axis direction in which the pair of static magnetic field magnets are opposed each other, and an annular magnetic pole configured to generate a static magnetic field on an X-Y plane perpendicular to the Z axis direction, and each gradient magnetic field coil includes a Z coil configured to provide a magnetic field being gradient in the Z axis direction in the imaging region, a magnetic material block configured to shield the discoid magnetic pole from a magnetic flux generated from the Z coil, and a correction coil configured to shield the annular magnetic pole from the magnetic flux generated from the Z coil. ### Claim 2 (depends on 1) The open-type magnetic resonance imaging apparatus according to claim 1, wherein the each static magnetic field magnet includes: an annular main coil configured to generate the static magnetic field in the Z axis direction; and a shield coil configured to reduce a magnetic field outside the open-type magnetic resonance imaging apparatus. ### Claim 3 (depends on 1) The open-type magnetic resonance imaging apparatus according to claim 1, wherein the each gradient magnetic field coil includes: an X coil configured to provide a magnetic field being gradient in an X axis direction in the imaging region; and a Y coil configured to provide a magnetic field being gradient in a Y axis direction in the imaging region. ### Claim 4 (depends on 1) The open-type magnetic resonance imaging apparatus according to claim 1, further comprising: an RF coil configured to apply a radiofrequency electromagnetic pulse to the static magnetic field in the imaging region. ### Claim 5 (depends on 1) The open-type magnetic resonance imaging apparatus according to claim 1, further comprising: a movable bed configured to convey a test subject into the imaging region of the open-type magnetic resonance imaging apparatus. ### Claim 6 (depends on 1) The open-type magnetic resonance imaging apparatus according to claim 1, wherein the correction coil is arranged radially outside of the Z coil, and the correction coil is arranged at the same height in the Z axis direction as the Z coil. ### Claim 7 (depends on 1) The open-type magnetic resonance imaging apparatus according to claim 1, wherein the each magnetic material block includes sheet magnetic materials which are stacked on each other in the Z axis direction and arranged side by side in a tile-like formation in an X axis direction and in a Y axis direction perpendicular to the Z axis direction. ### Claim 8 (depends on 7) The open-type magnetic resonance imaging apparatus according to claim 7, wherein the sheet magnetic material of the magnetic material block includes a silicon steel plate. ### Claim 9 (depends on 7) The open-type magnetic resonance imaging apparatus according to claim 7, wherein the magnetic material block has a thickness of 20 mm or more. ### Claim 10 (depends on 1) The open-type magnetic resonance imaging apparatus according to claim 1, wherein the Z coil is formed in an annular shape about the Z axis. ### Claim 11 (depends on 2) The open-type magnetic resonance imaging apparatus according to claim 2, wherein the shield coil is arranged radially outside of the main coil and configured to generate a magnetic field which has an opposite polarity to a polarity of the magnetic field in the imaging region. ### Claim 12 (depends on 3) The open-type magnetic resonance imaging apparatus according to claim 3, wherein the each X coil includes two coils which are arranged in the X axis direction with the Z axis interposed between the two coils, and the each Y coil includes two coils arranged in the Y axis direction with the Z axis interposed between the two coils. ### Claim 13 (depends on 4) The open-type magnetic resonance imaging apparatus according to claim 4, further comprising: a receiver coil configured to receive a magnetic resonance-related signal from a test subject in response to application of a radiofrequency electromagnetic pulse to the test subject by the RF coil. ### Claim 14 (depends on 2) The open-type magnetic resonance imaging apparatus according to claim 2, wherein the correction coil is arranged radially outside of the Z coil, and the correction coil is arranged at the same height in the Z axis direction as the Z coil. ### Claim 15 (depends on 3) The open-type magnetic resonance imaging apparatus according to claim 3, wherein the correction coil is arranged radially outside of the Z coil, and the correction coil is arranged at the same height in the Z axis direction as the Z coil.