# US 2013/0154648 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 2013/0154648 A1 - Document ID: US20130154648A1 - Status: Published application - Kind: A1 - Application number: 13/690,312 - Filed: 2012-11-30 - Published: 2013-06-20 - Earliest claimed: 2011-12-20 - Assignees: General Electric Company - Inventors: Weijun Shen; Timothy J. Havens; Longzhi Jiang; Tesfaye K. Kidane - Web page: https://patentgrep.com/patent/US20130154648A1 ## CPC - G01R 33/34092: {RF coils specially adapted for NMR spectrometers} - G01R 33/389: Field stabilisation {, e.g. by field measurements and control means or indirectly by current stabilisation} - G01R 33/56509: {due to motion, displacement or flow, e.g. gradient moment nulling (G01R33/567 takes precedence)} - G01R 33/56518: {due to eddy currents, e.g. caused by switching of the gradient magnetic field} - 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 vacuum vessel, a helium vessel disposed within the vacuum vessel and a thermal shield disposed between the vacuum vessel and the helium vessel. A set of passive compensation coils are disposed within the vacuum vessel or the helium 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 vacuum vessel; a helium vessel disposed within the vacuum vessel; a thermal shield disposed between the vacuum vessel and the helium vessel; 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 helium vessel 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 helium vessel. ### Claim 7 (depends on 1) A magnet apparatus according to claim 1, wherein the helium vessel 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 helium vessel. ### 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 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 9 (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 10 A magnet apparatus for a magnetic resonance imaging system, the magnet apparatus comprising: a vacuum vessel; a helium vessel disposed within the vacuum vessel; a thermal shield disposed between the vacuum vessel and the helium vessel; and a set of passive compensation coils disposed within the helium vessel. ### Claim 11 (depends on 10) A magnet apparatus according to claim 10, 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 12 (depends on 10) A magnet apparatus according to claim 10, wherein the passive compensation coils are superconducting coils. ### Claim 13 (depends on 12) A magnet apparatus according to claim 12, wherein the passive compensation coils are constructed from a low temperature superconducting material. ### Claim 14 (depends on 12) A magnet apparatus according to claim 12, wherein the passive compensation coils are constructed from a high temperature superconducting material.\ ### Claim 15 (depends on 10) A magnet apparatus according to claim 10, further comprising: a main coil former disposed inside the helium vessel; and wherein the set of passive compensation coils are positioned inside of the main coil former. ### Claim 16 (depends on 10) A magnet apparatus according to claim 10, further comprising: a main coil former disposed inside the helium vessel and having an outer surface; and wherein the set of passive compensation coils are positioned on the outer surface of the main coil former. ### Claim 17 (depends on 10) A magnate apparatus according to claim 10, further comprising” a bucking coil former disposed inside the helium vessel; and wherein the set of passive compensation coils are positioned inside of the bucking coil former. ### Claim 18 (depends on 10) A magnet apparatus according to claim 10, further comprising: a bucking coil former disposed inside the helium vessel and having an outer surface; and wherein the set of passive compensation coils are positioned on the outer surface of the bucking coil former. ### Claim 19 (depends on 10) A magnet apparatus according to claim 10, further comprising: a shim coil former disposed inside the helium vessel and having an outer surface; and wherein the set of passive compensation coils are positioned on the outer surface of the shim coil former. ### Claim 20 (depends on 10) A magnet apparatus according to claim 10, further comprising: a passive compensation coil former disposed inside the helium vessel and having an outer surface; and wherein the set of passive compensation coils are positioned on the outer surface of the passive compensation coil former.