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A TWO LAYER SHIM HOLDER FOR A MAGNETIC RESONANCE MAGNET

IP.com Disclosure Number: IPCOM000166563D
Publication Date: 2008-Jan-17
Document File: 4 page(s) / 116K

Publishing Venue

The IP.com Prior Art Database

Abstract

A two-layer shim holder for MR magnet for providing homogenous magnetic fields is disclosed herewith. The new shim holder comprises two layers namely base disk and cover disk. Holders for shim chips are integrated on the base disk with blind via hole and protruding ring and the shimming chips are covered by the cover disk with concave blind holes in corresponding position of protruding rings. The total height of base disk and cover disk is decreased compared to the three layer structure without decreasing of the mechanical strength of base and cover disk.

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A TWO LAYER SHIM HOLDER FOR A MAGNETIC RESONANCE MAGNET

FIELD OF INVENTION

[0001]               The invention generally relates to a method and system for providing homogenous magnetic fields and more specifically to a two layer shim holder for an MR magnet for facilitating shimming.

BACK GROUND OF THE INVENTION

[0002]               A homogenous magnetic field is very essential for operation of MR imaging systems. To get a homogeneous magnetic field in the field of view of a MRI magnetic field generator, especially a permanent magnet system, the magnetic field is usually adjusted by shim chips. The shim chips are generally installed on the pole piece under the gradient coil at factory. An example is illustrated in FIG.1. Factory shimming is usually not touched at field. But the magnetic field could be easily affected by the surrounding environments like temperature, iron structures in the scan room, etc.  Shimming at field is still required.

[0003]               Some of the solutions in the industry suggest providing a shim holder with 3-layer thin structure installed on the gradient coil. The magnetic field could be adjusted without detaching the gradient coil mounted on the pole pieces, illustrated in FIG.2. However the disadvantage of this structure is that the space required for the 3-layer thin structure increases the air gap between the two pole pieces that mainly determines the total weight of permanent magnet block used in the MR system. The larger air gap required, the more PM block used, and hence more expensive the magnet is.

[0004]               Thus there exist a need to provide a method and system for providing a homogeneous magnetic field.

SUMMARY OF INVENTION

[0005]               An embodiment of the invention provides a method and system for providing homogenous magnetic field in a pregnant magnet system. This is achieved by suggesting a new structure for providing shimming.

[0006]               In another embodiment the invention provides a method for providing shimming at field with lesser space required between the two pole-pieces.

[0007]               In an embodiment a two-layer thin plate structure is disclosed wherein the shim chip holder is integrated into the layer of base disk and cover disk

[0008]               Though the invention mentions about MR imaging system, the invention could be used with any equipment, where there exist a permanent magnet structure and there is need for homogenous magnetic field.

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