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Treatment of eddy current on polar plate in permanent magnet device of magnetic resonance imaging system

A technology of magnetic resonance imaging and permanent magnets, applied in applications, medical science, sensors, etc., can solve problems such as strong eddy currents, unsatisfactory effects, and increased cost of nuclear magnetic resonance imaging systems, and achieve the effect of suppressing eddy currents and improving imaging quality

Inactive Publication Date: 2003-03-05
WUHAN HONGJIAN ELECTRIC TECH
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Problems solved by technology

In comparison, the former method will increase the cost of the MRI system more, while the latter method is more economical
In the permanent magnet with traditional structure, the pole plate is usually made of a whole piece of soft iron plate with high magnetic permeability. The pole plate of this structure is not only a good conductor of magnetism but also a good conductor of electricity, which will cause strong eddy current
In order to reduce the eddy current in the pole plate, the improved magnet is bonded with a layer of soft ferrite with an appropriate thickness on the surface of the pole plate. Since the saturation magnetic induction of soft ferrite is relatively low, this method is suitable for magnets with relatively low magnetic field strength. The eddy current has a certain inhibitory effect, and the effect of this method is not ideal for magnets with slightly higher magnetic field strength

Method used

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  • Treatment of eddy current on polar plate in permanent magnet device of magnetic resonance imaging system
  • Treatment of eddy current on polar plate in permanent magnet device of magnetic resonance imaging system
  • Treatment of eddy current on polar plate in permanent magnet device of magnetic resonance imaging system

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Embodiment Construction

[0017] The plate body is made of low-carbon steel, and its shape is circular, stepped or rectangular; the isolation layer is made of high magnetic resistance and high resistance material. The core part of the filter layer is coiled into a plate shape by silicon steel sheet and insulating material; or coiled into a plate shape by iron-nickel alloy and insulating material; or coiled into a plate shape by iron-aluminum alloy and insulating material.

[0018] The core part of the filter layer is made of silicon steel sheets (or similar materials) and insulating materials stacked into small squares and then bonded and assembled. The shape of the filter layer is basically the same as that of the said pole plate body; the peripheral part of the filter layer is made of low carbon steel so as to facilitate the connection of the filter layer and the pole plate body and limit the aforementioned small squares within the conceived range. The stacking method of the said small squares is: si...

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Abstract

The method of treating eddy current on the polar plate in permanent magnet device of nuclear magnetic resonance imaging system is characterized by that the polar plate (component) of its permanent magnet is formed from polar plate body, filtering layer, isolating layer for separating polar plate body and filtering layer, protecting layer for protecting filtering layer and uniform filed ring. It can make the eddy current be filtered off in the filtering layer, and make it do not infiltrate into the polar plate, and between filtering layer and polar plate body there are higher electric resistance and magnetic resistance, and the filtering layer material and insulating material mixed and overlapped direction is perpendicular to the direction of magnet working space magnetic field. Said invention can effectively inhibit eddy current so as to greatly can raise imaging quality.

Description

technical field [0001] The invention relates to a magnet applied to a magnetic resonance imaging system which requires controlling the eddy current within a certain range. Background technique [0002] In order to quickly obtain clear and true images for accurate diagnosis of patients, the magnetic resonance imaging system requires that the magnets in it can provide a very uniform spatial magnetic field distribution in a wide range while minimizing the eddy currents generated on the magnets during the imaging process. For magnets with pole plates, the most critical for this purpose is the design of the magnet pole plates. [0003] During the imaging process of the nuclear magnetic resonance imaging system, it can be known from the law of electromagnetic induction that when a pulse gradient magnetic field is applied, electromagnetic induction (ie, eddy current) will be generated in the conductor in the changing electromagnetic field. The size of the eddy c...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): A61B5/055
Inventor 李建久
Owner WUHAN HONGJIAN ELECTRIC TECH
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