公开(公告)号：US06239599B1

公开(公告)日：2001-05-29

申请号：US09316344

申请日：1999-05-21

申请人： Xiaohong Zhou ,  Joseph K. Maier ,  Steven J. Huff

发明人： Xiaohong Zhou ,  Joseph K. Maier ,  Steven J. Huff

IPC分类号： G01V300

CPC分类号： G01R33/58 ,  G01R33/56518 ,  G01R33/56554

摘要： A technique is disclosed for determining errors in MRI sequences resulting from eddy currents generated by pulsed gradient fields. During a calibration sequence, with no phase-encoding, gradient pulses and readout sequences are applied along physical axes of a scanner and data sets are acquired for each combination. A reference data set is acquired with no gradient pulses applied. The resulting data sets are processed by one dimensional Fourier transformation, and the transformed data is analyzed to determine spatially invariant and linear gradient errors. The phase errors may be averaged for each physical axis. The technique is particularly useful in determining errors in diffusion weighted echo planar imaging sequences.

摘要翻译： 公开了一种用于确定由脉冲梯度场产生的涡流产生的MRI序列中的误差的技术。 在校准序列期间，没有相位编码，沿着扫描仪的物理轴施加梯度脉冲和读出序列，并为每个组合采集数据集。 在不施加梯度脉冲的情况下获取参考数据集。 通过一维傅里叶变换处理所得到的数据集，并分析变换数据以确定空间不变和线性梯度误差。 每个物理轴可以对相位误差进行平均。 该技术在确定扩散加权回波平面成像序列中的误差方面特别有用。

公开(公告)号：US6100689A

公开(公告)日：2000-08-08

申请号：US145932

申请日：1998-09-03

申请人： Steven J. Huff ,  Joseph K. Maier ,  Anders Per Olof Hornblad ,  Gopal B. Avinash

发明人： Steven J. Huff ,  Joseph K. Maier ,  Anders Per Olof Hornblad ,  Gopal B. Avinash

IPC分类号： G01R33/56 ,  G01R33/565 ,  G01V3/00

CPC分类号： G01R33/56 ,  G01R33/565

摘要： The ghost artifacts appearing in images produced by an MRI system are measured. An image of a reference phantom is acquired and the ghost artifacts are measured by cross correlating a ghost correlation matrix with the image. The ghost correlation matrix is produced from the image and the cross correlation is computed as the ghost correlation matrix is moved across the image along either the phase encoding or frequency encoding axes.

摘要翻译： 测量由MRI系统产生的图像中出现的鬼影。 获取参考体模的图像，并通过将重影相关矩阵与图像交叉相关来测量幻影伪影。 根据图像产生重影相关矩阵，并且当相关矩阵沿着相位编码或频率编码轴在图像上移动时，计算互相关。

公开(公告)号：US06528998B1

公开(公告)日：2003-03-04

申请号：US09540768

申请日：2000-03-31

申请人： Xiaohong Zhou ,  Joseph K. Maier ,  Steven J. Huff

发明人： Xiaohong Zhou ,  Joseph K. Maier ,  Steven J. Huff

IPC分类号： G01V300

CPC分类号： G01R33/56581

摘要： A method and apparatus for correcting ghosting artifacts that are related to Maxwell fields and/or other perturbation magnetic fields is disclosed. The method and apparatus includes acquiring MR image n-space data and an MR reference scan, each having perturbation field effects therein. After determining phase correction values from the MR reference scan and reconstructing an MR image using the phase correction values, a projection phase error is calculated from the reconstructed MR image and then subtracted from the reference scan, the result of which is used to determine a new set of phase correction values. The new set of phase correction values is applied to the acquired MR image data to reconstruct a new image. The reconstructed new image can then be reused to calculate a new projection phase error, which again is subtracted from the reference scan data and the process is repeated until an image of desired ghost artifact reduction is achieved.

摘要翻译： 公开了一种用于校正与麦克斯韦尔场和/或其他扰动磁场相关的重影伪像的方法和装置。 该方法和装置包括获取每个在其中具有扰动场效应的MR图像n空间数据和MR参考扫描。 在从MR参考扫描确定相位校正值并使用相位校正值重建MR图像之后，从重建的MR图像计算投影相位误差，然后从参考扫描中减去其结果，其结果用于确定新的 一组相位校正值。 将新的相位校正值集合应用于所获取的MR图像数据以重构新图像。 然后可以重新构建重建的新图像以计算新的投影相位误差，其再次从参考扫描数据中减去，并且重复该过程，直到实现期望的鬼影伪像减少的图像。

公开(公告)号：US06469505B1

公开(公告)日：2002-10-22

申请号：US09540687

申请日：2000-03-31

申请人： Joseph K. Maier ,  Xiaohong Zhou ,  Steven J. Huff

发明人： Joseph K. Maier ,  Xiaohong Zhou ,  Steven J. Huff

IPC分类号： G01V300

CPC分类号： G01R33/56563 ,  G01R33/5604 ,  G01R33/56518

摘要： A method and apparatus for correcting ghost artifacts that are related to orthogonal perturbation magnetic fields is disclosed. The technique includes acquiring MR data and an MR reference scan, each in the presence of orthogonal perturbation magnetic fields. However, the region of interest for the MR reference scan is limited to a relatively narrow band within the imaging subject. Preferably, the narrow band is selected in the vicinity of the magnet iso-center and parallel to the readout direction. Alternatively, the narrow band can also be selected in the limited region where the orthogonal perturbation fields are either minimal or constant along the phase encoding direction, and parallel to the readout direction. The selection of the relatively narrow band is accomplished by either spatially saturating surrounding regions, or using a two-dimensional spatially selective RF pulse. Phase correction values can then be calculated from a more accurately defined slope and intercept of the phase of the MR reference scan and used to correct the MR data. A reconstructed MR image using this technique has reduced ghost artifacts otherwise caused by the adverse effects of the orthogonal perturbation fields in the phase correction process.

摘要翻译： 公开了一种用于校正与正交扰动磁场相关的重影伪影的方法和装置。 该技术包括获取MR数据和MR参考扫描，每个在存在正交扰动磁场的情况下。 然而，用于MR参考扫描的感兴趣区域被限制在成像对象内的相对较窄的频带。 优选地，在磁体等中心附近并且平行于读出方向选择窄带。 或者，也可以在有限区域选择窄带，其中正交扰动场沿相位编码方向为最小或恒定，并且平行于读出方向。 通过空间饱和的周围区域或使用二维空间选择性RF脉冲来实现相对窄带的选择。 然后可以从更准确地定义的MR参考扫描的相位的斜率和截距来计算相位校正值，并用于校正MR数据。 使用该技术的重构MR图像减少了由相位校正处理中的正交扰动场的不利影响引起的鬼影。

公开(公告)号：US06323646B1

公开(公告)日：2001-11-27

申请号：US09316230

申请日：1999-05-21

申请人： Xiaohong Zhou ,  Joseph K. Maier ,  Steven J. Huff ,  Hammond Glenn Reynolds

发明人： Xiaohong Zhou ,  Joseph K. Maier ,  Steven J. Huff ,  Hammond Glenn Reynolds

IPC分类号： G01V300

CPC分类号： G01R33/56341

摘要： A technique is provided for generating images on an MRI system in which errors due to gradient pulses are compensated. The errors are identified in advance, such as in a calibration sequence performed on the MRI system. Receiver phase adjustment and logical gradient error values are derived from the identified error values. The calibration sequence may be a modified version of the MRI imaging sequence used to produce the images. The correction values may be based upon corrections at the center of k-space. The technique is particularly useful in compensating for effects of eddy currents in pulse sequences employing high slew rate gradient pulses, such as diffusion weighted echo planar imaging sequences.

摘要翻译： 提供了一种用于在MRI系统上生成图像的技术，其中补偿了由于梯度脉冲引起的误差。 错误是事先确定的，例如在MRI系统上执行的校准序列。 接收器相位调整和逻辑梯度误差值是从识别的误差值导出的。 校准序列可以是用于产生图像的MRI成像序列的修改版本。 校正值可以基于在k空间中心的校正。 该技术在补偿使用高压摆率梯度脉冲（例如扩散加权回波平面成像序列）的脉冲序列中对涡流的影响特别有用。