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SYSTEM AND METHOD FOR PASSIVE SHIM TRAY FORCE REDUCTION

IP.com Disclosure Number: IPCOM000216296D
Publication Date: 2012-Mar-29
Document File: 4 page(s) / 126K

Publishing Venue

The IP.com Prior Art Database

Abstract

A system and method for passive shim tray force reduction using high temperature super conducting (HTS) bulks is provided. HTS bulks such as Yttrium Barium Copper Oxide (YBCO) bulks can trap strong magnetic fields after magnetization. HTS bulks can be inserted into the energized magnet at room temperature and subsequently cooled with cryo-cooler or liquid nitrogen. Use of HTS bulks, alleviates issues of force experienced during shim tray insertion or extraction, thereby providing a safer and easier system and method for passive shimming.

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SYSTEM AND METHOD FOR PASSIVE SHIM TRAY FORCE REDUCTION

FIELD OF INVENTION

The invention generally relates to passive shimming and more particularly to system and method for reducing high forces experienced during the insertion or extraction of shim trays.

BACKGROUND OF THE INVENTION

Magnetic resonance (MR) magnets are designed to create a uniform field. However, manufacturing variations and ambient ferromagnetic materials cause undesirable inhomogeneous magnetic fields. Inhomogeneous magnetic field hampers imaging performance of an MR system.

Inhomogeneous magnetic fields are generally corrected using an array of ferromagnetic shims placed within the bore of the magnet. Such shims, referred to as passive shims are usually placed in the annular space between the primary gradient and the gradient shield or in the annular space between the magnet and the gradient coil.

Such passive shimming is an iterative process and usually requires several process cycles to meet the homogeneity requirements. De-energizing the magnet takes time and consumes expensive helium. Therefore, it is highly desirable to be able to modify the shim distribution while the magnet is at field. To facilitate modification of shim distribution while the magnet is at field, shim pieces are usually mounted on trays or drawers, referred to as shim trays, which can be withdrawn from an end of the magnet. During insertion or extraction of the shim trays, high forces are experienced which can be dangerous for a field engineer.


Page 02 of 4

Hence there exists a need for an improved system and method for passive shimming that reduces high forces experienced during the insertion or extraction of shim trays.

BRIEF DESCRIPTION OF THE INVENTION

A system and method for passive shim tray force reduction using high temperature super conducting (HTS) bulks is provided. HTS bulks such as Yttrium Barium Copper Oxide (YBCO) bulks trap strong magnetic fields after magnetization.The HTS bulks can be

inserted at room temperature. Therefore there is no electromagnetic force during shim tray insertion or extraction. Use of HTS bulks makes the shim tray insertion much safer and easier. In addition, since the HTS bulks work at cryogenic temperature, there is no concern about B0 drift caused by temperature rise in shims.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a sy...