Electricity: magnetically operated switches – magnets – and electr – Magnets and electromagnets – Magnet structure or material
Patent
1998-12-07
1999-10-05
Gellner, Michael L.
Electricity: magnetically operated switches, magnets, and electr
Magnets and electromagnets
Magnet structure or material
335296, 335297, 324319, H01F 702
Patent
active
059631171
ABSTRACT:
Proposed is an improvement in an opposed-magnet magnetic circuit assembly with permanent magnets suitable for use, for example, in an MRI instrument comprising a pair of upper and lower permanent magnets to form a magnetic-field gap space therebetween, a pair of magnetic-field adjustment plates each on the surface of the permanent magnet to face the gap space and a pair of back yokes each on the back surface of the permanent magnet. According to the first aspect of the invention, a combination of a gradient coil and a shimming plate is mounted on the magnetic-field adjustment plate with intervention of several pieces of shim members and, further, another set of second shim members are bonded to the surface of the shimming plate facing the gap space with an object to improve the uniformity of the magnetic field in the gap space. According to the second aspect of the invention, which is directed to the problem of alleviation of the oppressive sense received by the patient lying in the MRI instrument due to his encaved condition, the back yokes are magnetically and mechanically connected with two and only two columnar connecting yokes each of which has a smaller cross section in the center portion than in the upper and lower end portions in order to ensure lateral openness on both sides of the patient. Preferable configurations are also proposed for the back yokes and the permanent magnets.
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Inoue Yuji
Miyata Koji
Ohashi Ken
Yoneda Yuhito
Barrera Raymond
GE Yokogawa Medical Systems, Ltd.
Gellner Michael L.
Shin-Etsu Chemical Co. , Ltd.
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