Passive Shimming of MRI Static Magnetic Field Using Regularization of Truncated Singular Value Decomposition.
Passive Shimming of MRI Static Magnetic Field Using Regularization of Truncated Singular Value Decomposition.
复制标题
DOI：
10.2463/mrms.mp.2016-0046
复制
发表时间：
2017-10-10
期刊：
影响因子：
--
通讯作者：
Abe M
中科院分区：
文献类型：
--
作者：
Abe M
开发一种新的匀场计算方法，可以快速计算出铁件的位置，使磁场均匀在预定的均匀度，从而缩短匀场工作时间。匀场计算产生磁矩（MM）分布，其通过从测量的磁场的截断奇异值分解（SVD）来计算。的MM分布所描述的叠加本征模式通过SVD的响应矩阵从力矩分布磁场在视场（FOV）。均匀性由叠加本征模的截断数来调节。在饱和磁化假设下，将磁矩换算为铁体积，并根据计算结果进行铁件的放置。由于可以提前进行SVD计算，因此匀场位置的计算时间很短。在0.5T磁共振成像（MRI）磁体上进行了试验应用，结果表明该方法具有良好的匀场效果。然而，由于铁件体积具有公差，因此重复工作直到获得足够的均匀性。结果，在40 cm直径球面上的预期均匀度为8.9 ppm（峰-峰），成功地从543 ppm的测量均匀度获得，计算和工作时间较短。实验结果表明，本文提出的基于截断奇异值分解正则化的匀场计算方法适用于MRI磁体的匀场计算。
To develop a new shimming calculation method, which can calculate iron piece placements rapidly to make the magnetic field homogeneous at intended homogeneity and then to make the shimming working time short. The shimming calculation yields magnetic moment (MM) distribution, which is calculated by the truncated singular value decomposition (SVD) from the measured magnetic field. The MM distribution is described by a superposition of eigenmodes obtained by SVD of a response matrix from the moment distributions to magnetic fields at the field of view (FOV). The homogeneity is regulated by a truncation number of the superposed eigenmodes. The magnetic moments are converted into iron volumes with the assumption of saturated magnetization and the iron pieces are placed according to the calculation results. Since the SVD calculation can be done in advance, the computational time at the shimming site is short. Trial applications on a 0.5T magnetic resonance imaging (MRI) magnet were done using the new shimming calculation method, which was proved to work well. However, since the iron piece volumes had tolerances, the work was repeated until enough homogeneity was obtained. As a result, an intended homogeneity of 8.9 ppm (peak-to-peak) on 40 cm diameter spherical surface was successfully obtained from measured homogeneity of 543 ppm with short computational and working time. The test shimming work showed that the developed shimming calculation method with truncated SVD regularization is applicable to the shimming work on the MRI magnets.
登录
查看更多内容
影响因子：
2.1
作者：
Abe, Mitsushi
通讯作者：
Abe, Mitsushi
影响因子：
2.2
作者：
Terada, Y.;Kono, S.;Kose, K.
通讯作者：
Kose, K.
影响因子：
2.4
作者：
PISSANETZKY, S
通讯作者：
PISSANETZKY, S
影响因子：
1.8
作者：
Kakugawa, S;Hino, N;Tazaki, H
通讯作者：
Tazaki, H
DOI：
10.1002/cmr.b.20040
发表时间：
2005-08-01
影响因子：
0.9
作者：
Lemdiasov, RA;Ludwig, R
通讯作者：
Ludwig, R