Methods and apparatus for compensating for drift in magnetic field strength in superconducting magnets
OwnerNicholas Paul Aleyinventor
Life of this patent
Estimating the term…
Abstract
An MRI system has compensating material located at a radial position between the imaging region and the basic field magnet in a location that will be heated over a range of temperatures during operation of the MRI system. The compensating material has a magnetic susceptibility that varies with temperature over the range of temperatures in a manner opposite to the variation in magnetic susceptibility of the material of the OVC bore tube of the basic field magnet over the range of temperatures.
Claims48
A magnetic resonance imaging (MRI) system comprising:
- a cylindrical superconducting magnet assembly having a longitudinal axis;
- a cylindrical vacuum vessel (OVC) that contains the superconducting magnet assembly, said OVC having a bore tube therein comprised of bore tube material having a magnetic susceptibility and that is rotationally symmetrical about the longitudinal axis;
- a gradient coil assembly situated within the bore tube of the OVC, said gradient coil assembly having a coil assembly bore therein;
- said superconducting magnet assembly being configured to produce a magnetic field in an imaging region within said bore tube of said gradient coil assembly, said magnetic field in said imaging region exhibiting a field property that is subject to drift due to heating that occurs during operation of said MRI system that causes said magnetic susceptibility of said bore tube material to change;
- compensating material situated at a radial position, relative to said longitudinal axis, between the imaging region and the superconducting magnet assembly at a location that is subject to heating over a range of temperatures due to said heating that occurs during said operation of the MRI system;
- and
- said compensating material having a magnetic susceptibility that changes with temperature, within said range of temperature oppositely to said change in magnetic susceptibility of said bore tube material, to compensate said drift.
A method for operating an MRI system comprising a cylindrical superconducting magnet assembly having a longitudinal axis, a cylindrical vacuum vessel (OVC) that contains the superconducting magnet assembly, said OVC having a bore tube therein comprised of bore tube material having a magnetic susceptibility and that is rotationally symmetrical about the longitudinal axis, a gradient coil assembly situated within the bore tube of the OVC, said gradient coil assembly having a coil assembly bore therein, said superconducting magnet assembly being configured to produce a magnetic field in an imaging region within said bore tube of said gradient coil assembly, said magnetic field in said imaging region exhibiting a field property that is subject to drift due to heating that occurs during operation of said MRI system that causes said magnetic susceptibility of said bore tube material to change, said method comprising:
- situating compensating material at a radial position, relative to said longitudinal axis, between the imaging region and the superconducting magnet assembly at a location that is subject to heating over a range of temperatures due to said heating that occurs during said operation of the MRI system;
- and
- selecting said compensation material to have a magnetic susceptibility that changes with temperature, within said range of temperature oppositely to said change in magnetic susceptibility of said bore tube material, to compensate said drift.
Dependencies are inferred from the claim text.