# US 2014/0155268 A1 · System and apparatus for compensating for magnetic field distortion in an mri system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0155268 A1 - Document ID: US20140155268A1 - Status: Published application - Kind: A1 - Application number: 13/690,392 - Filed: 2012-11-30 - Published: 2014-06-05 - Earliest claimed: 2012-11-30 - Assignees: General Electric Company - Applicants: General Electric Company - Inventors: Weijun Shen; Timothy J. Havens; Longzhi Jiang; Tesfaye K. Kidane - Web page: https://patentgrep.com/patent/US20140155268A1 ## CPC - G01R 33/34023: {Superconducting RF coils} - G01R 33/387: Compensation of inhomogeneities - G01R 33/3815: with superconducting coils, e.g. power supply therefor - G01R 33/3875: using correction coil assemblies, e.g. active shimming - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract A magnet apparatus for a magnetic resonance imaging system, the magnet apparatus includes a cylindrical vacuum vessel, a closed loop cooling system disposed within the vacuum vessel and a cylindrical thermal shield disposed between the vacuum vessel and the closed loop cooling system. A set of passive compensation coils are disposed within the vacuum vessel and used to compensate for magnetic field distortion caused by mechanical vibrations within the magnet apparatus. ## Claims ### Claim 1 A magnet apparatus for a magnetic resonance imaging system, the magnet apparatus comprising: a cylindrical vacuum vessel; a closed loop cooling system disposed within the vacuum vessel; a cylindrical thermal shield disposed between the vacuum vessel and closed loop cooling system; and a set of passive compensation coils disposed within the vacuum vessel. ### Claim 2 (depends on 1) A magnet apparatus according to claim 1, wherein the set of passive compensation coils comprises: a first set of passive compensation coils for a z-axis direction; a second set of passive compensation coils for a y-axis direction; and a third set of passive compensation coils for an x-axis direction. ### Claim 3 (depends on 1) A magnet apparatus according to claim 1, wherein the passive compensation coils are superconducting coils. ### Claim 4 (depends on 3) A magnet apparatus according to claim 3, wherein the passive compensation coils are constructed from a low temperature superconducting material. ### Claim 5 (depends on 3) A magnet apparatus according to claim 3, wherein the passive compensation coils are constructed from a high temperature superconducting material. ### Claim 6 (depends on 1) A magnet apparatus according to claim 1, wherein the thermal shield comprises an outer cylinder and an inner cylinder, the outer cylinder having an outer surface and the set of passive compensation coils disposed on the outer surface of the outer cylinder of the thermal shield. ### Claim 7 (depends on 1) A magnet apparatus according to claim 1, wherein the thermal shield comprises an outer cylinder and an inner cylinder, the inner cylinder having an outer surface and the set of passive compensation coils disposed on the outer surface of the inner cylinder of the thermal shield ### Claim 8 (depends on 1) A magnet apparatus according to claim 1, wherein the thermal shield comprises an outer cylinder and an inner cylinder, the inner cylinder having an inner surface and the set of passive compensation coils disposed on the inner surface of the inner cylinder of the thermal shield ### Claim 9 (depends on 1) A magnet apparatus according to claim 1, wherein the thermal shield comprises an outer cylinder and an inner cylinder, the outer cylinder having an inner surface and the set of passive compensation coils disposed on the inner surface of the outer cylinder of the thermal shield ### Claim 10 (depends on 1) A magnet apparatus according to claim 1, further comprising: a main coil former disposed inside the vacuum vessel and having an outer diameter; and wherein the set of passive compensation coils are positioned on the outer diameter of the main coil former ### Claim 11 (depends on 1) A magnet apparatus according to claim 1, further comprising: a bucking coil former disposed inside the vacuum vessel and having an outer diameter; and wherein the set of passive compensation coils are positioned on the outer diameter of the bucking coil former. ### Claim 12 A magnet apparatus for a magnetic resonance imaging system, the magnet apparatus comprising: a cylindrical vacuum vessel; at least one cylindrical coil former disposed within the vacuum vessel, the at least one coil former having at least one superconducting coil mounted thereon; a cylindrical thermal shield disposed between the vacuum vessel and the at least one coil former; and a set of passive compensation coils disposed within the vacuum vessel. ### Claim 13 (depends on 12) A magnet apparatus according to claim 12, wherein the set of passive compensation coils comprises: a first set of passive compensation coils for a z-axis direction; a second set of passive compensation coils for a y-axis direction; and a third set of passive compensation coils for an x-axis direction. ### Claim 14 (depends on 12) A magnet apparatus according to claim 12, wherein the passive compensation coils are superconducting coils. ### Claim 15 (depends on 14) A magnet apparatus according to claim 14, wherein the passive compensation coils are constructed from a low temperature superconducting material. ### Claim 16 (depends on 14) A magnet apparatus according to claim 14, wherein the passive compensation coils are constructed from a high temperature superconducting material. ### Claim 17 (depends on 12) A magnet apparatus according to claim 12, wherein the at least one coil former comprises a main coil former disposed inside the vacuum vessel and having an outer diameter and the set of passive compensation coils are positioned on the outer diameter of the main coil former. ### Claim 18 (depends on 12) A magnet assembly according to claim 12, wherein the at least one coil former comprises a bucking coil former disposed inside the vacuum vessel and having an outer diameter and the set of passive compensation coils are positioned on the outer diameter of the bucking coil former.