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1. 发明授权

US5418462A Method for determining shim placement on tubular magnet 失效
标题翻译：确定管状磁铁上垫片放置的方法
公开(公告)号：US5418462A
公开(公告)日：1995-05-23
申请号：US237256
申请日：1994-05-02
申请人： Bruce C. Breneman , Yen-Hwa Hsu , Jang-Yu Hsu
发明人： Bruce C. Breneman , Yen-Hwa Hsu , Jang-Yu Hsu
IPC分类号： A61B5/055 , G01R33/24 , G01R33/3873 , G01V3/00
CPC分类号： G01R33/3873 , G01R33/24
摘要： A method for using ferromagnetic shims to reduce the inhomogeneity of the magnetic field in a Diameter Spherical Volume (DSV) in the bore of a Magnetic Resonance Imaging (MRI) device is provided. More specifically, a magnetic field is established within the bore of the MRI device. An operator defines the DSV. The strength of the magnetic field is measured at the surface of the DSV. A Legendre polynomial is derived to model the inhomogeneity in the magnetic field in the DSV. A set of coefficients for the harmonic terms of the polynomial is calculated from the field strength measurements and segregated into three separate groups for evaluation. Each group of terms expresses field inhomogeneity in a unique set of spatial dimensions. Ferromagnetic shims are attached to the surface of the bore in individual dipole, linear bar, and ring arrangements to separately reduce the first, second, and third groups of harmonic coefficients to acceptable levels corresponding to a predetermined peak-to-peak inhomogeneity range.
摘要翻译：提供了一种使用铁磁垫片来减少磁共振成像（MRI）装置的孔中的直径球体积（DSV）中的磁场的不均匀性的方法。更具体地，在MRI装置的孔内建立磁场。操作员定义DSV。在DSV的表面测量磁场的强度。导出勒让德多项式来模拟DSV中磁场的不均匀性。从场强测量中计算出多项式谐波项的一组系数，并将其分离为三个独立的组进行评估。每一组术语在一组独特的空间维度中表现出场不均匀性。铁磁垫片以单独的偶极子，线性杆和环形布置附接到孔的表面，以将第一，第二和第三组谐波系数分别地减小到对应于预定的峰 - 峰不均匀性范围的可接受的水平。

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