Ferromagnetic shield for magnetic resonance imaging
AssigneeKoninklijke Philips Electronics N.V.
InventorBenjamin Hendricus Aarts
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Abstract
A cryocooler assembly includes a ferromagnetic shield and a moveable rare-earth regenerator for recondensing of a cooling liquid for cooling of a superconductive magnet of a magnetic resonance imaging apparatus. The ferromagnetic shield effectively provides depletion of a magnet field in the vicinity of the rare-earth regenerator and therefore on the one hand reduces the noise impact of the moving regenerator on the homogeneous magnetic field in the imaging volume of the MRI apparatus and on the other hand reduces the mechanical force exerted by the magnetic field on the rare-earth regenerator.
Claims19
A cryocooler assembly having a rare-earth regenerator for recondensing of a cooling liquid for cooling of a superconductive magnet or for directly cooling the superconductive magnet coils of a magnetic resonance imaging apparatus, wherein the cryocooler assembly comprises a shield of ferromagnetic material at least partially surrounding the rare-earth regenerator, wherein the rare-earth regenerator is adapted to move between a cold region and a hotter region, wherein the shield of ferromagnetic material is adapted to generate a magnetic field between the cold and hotter region from the magnetic field of the superconductive magnet so that the magnetic field induces a magnetic moment in the rare-earth regenerator which compensates for a change of the magnetic moment of the rare-earth regenerator caused by the movement of the rare-earth regenerator between the cold region and the hotter region, wherein the shield of ferromagnetic material is arranged so that the cross sectional area enclosed by the inner surface of the shield is of circular form and so that the cross sectional area enclosed by the outer surface of the shield is of elliptical form.
A cryocooler assembly having a rare-earth regenerator which moves between a cold region and a hotter region for recondensing of a cooling liquid for cooling of a superconductive magnet or for directly cooling the superconductive magnet coils of a magnetic resonance imaging apparatus, the cryocooler assembly comprising:
- a shield of ferromagnetic material at least partially surrounding the rare-earth regenerator, the shield of ferromagnetic material including a plurality of layers of ferromagnetic material.
A cryocooler assembly having a rare-earth regenerator adapted to move between a cold region and a hotter region to recondense a cryogenic cooling fluid for cooling of a superconductive magnet or to directly cool the superconductive magnet coils of a magnetic resonance apparatus, the cryocooler assembly comprising at least:
- a first shield of ferromagnetic material at least partially surrounding the rare-earth regenerator;
- and
- a second shield of ferromagnetic material which at least partially shields the rare-earth generator and the superconducting magnet coils from each other.
Dependencies are inferred from the claim text.