公开(公告)号：US06335620B1

公开(公告)日：2002-01-01

申请号：US09467948

申请日：1999-12-21

Applicant: Volker Weissenberger

Inventor： Volker Weissenberger

IPC: G01V300

CPC classification number: G01R33/56518

Abstract: In a method for acquiring eddy currents that are caused by switched magnetic field gradients and that contain cross-terms, at least the cross-terms can be determined from the selected slice within a short time, by the steps of introducing a spatially expansive phantom into the examination region of the magnetic resonance apparatus, activating a measuring gradient pulse that exhibits a prescribable pulse width, and after the deactivation of the measuring gradient pulse generating at least two imaging sequence blocks following one another at the spacings (t1, t2, tn) with at least two-dimensional, complex data set being generated from their imaging signals, the phase information contained therein being proportional to the magnetic field strength.

Abstract translation: 在用于获取由开关磁场梯度引起并且包含交叉项的涡流的方法中，至少可以在短时间内从选定的切片确定交叉项，通过将空间膨胀的体模引入到 磁共振装置的检查区域，激活呈现规定脉冲宽度的测量梯度脉冲，以及在以间隔（t1，t2，tn）彼此相继产生至少两个成像序列块的测量梯度脉冲失效之后， 其中至少二维，复数数据集是从其成像信号产生的，其中包含的相位信息与磁场强度成比例。

公开(公告)号：US20010017544A1

公开(公告)日：2001-08-30

申请号：US09770041

申请日：2001-01-25

Inventor： Shoei Miyamoto

IPC: G01V003/00

CPC classification number: G01R33/56518 ,  G01R33/56563

Abstract: The present invention aims to reduce degradation in image quality due to residual magnetization. In a pulse sequence of a high-speed spin echo process, a pre-pulse is applied before an excitation pulse, and a correction pulse for correcting a phase error caused by the pre-pulse is applied before an initial inversion pulse.

Abstract translation: 本发明旨在减少由剩余磁化引起的图像质量降低。 在高速自旋回波处理的脉冲序列中，在激励脉冲之前施加预脉冲，并且在初始反转脉冲之前施加用于校正由预脉冲引起的相位误差的校正脉冲。

公开(公告)号：US06239599B1

公开(公告)日：2001-05-29

申请号：US09316344

申请日：1999-05-21

Applicant: Xiaohong Zhou ,  Joseph K. Maier ,  Steven J. Huff

Inventor： Xiaohong Zhou ,  Joseph K. Maier ,  Steven J. Huff

IPC: G01V300

CPC classification number: G01R33/58 ,  G01R33/56518 ,  G01R33/56554

Abstract: 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.

Abstract translation: 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：US6163152A

公开(公告)日：2000-12-19

申请号：US97525

申请日：1998-06-15

Applicant: Matthew A. Bernstein ,  Jason A. Polzin

Inventor： Matthew A. Bernstein ,  Jason A. Polzin

IPC: A61B5/055 ,  G01R33/54 ,  G01R33/565 ,  G01V3/00

CPC classification number: G01R33/56518

Abstract: A system and method for correcting systematic errors that occur in MR images due to magnetic gradient non-uniformity is disclosed for use with parametric analysis. A GradWarp geometric correction operation is applied in reconstructing quantitative parametric analysis images in regions of gradient non-uniformity. The method includes generating an error map of magnetic gradient strength as a function of distance for an MR image scan and acquiring MR data that contain such systematic errors. The method next includes either calculating a measured diffusion image, a phase difference image, or similar image, based on the acquired MR data, and then calculating a corrected parametric image using the error map and the measured diffusion image, the phase difference image, or other similar parametric image. The method is incorporated into a system having a computer programmed to perform the aforementioned steps and functions.

Abstract translation: 公开了一种用于校正由于磁梯度不均匀性而在MR图像中发生的系统误差的系统和方法，用于参数分析。 应用GradWarp几何校正操作重建梯度不均匀区域的定量参数分析图像。 该方法包括产生磁梯度强度的误差图，作为MR图像扫描的距离的函数，并获取包含这种系统误差的MR数据。 该方法接下来包括基于获取的MR数据计算测量的漫射图像，相位差图像或类似图像，然后使用误差图和测量的漫射图像，相位差图像或 其他类似的参数图像。 该方法被并入具有被编程为执行上述步骤和功能的计算机的系统中。

公开(公告)号：US5942897A

公开(公告)日：1999-08-24

申请号：US775156

申请日：1996-12-31

Applicant: Hitoshi Kanazawa

Inventor： Hitoshi Kanazawa

IPC: G01R33/54 ,  A61B5/055 ,  G01R33/561 ,  G01R33/565 ,  G01V3/00

CPC classification number: G01R33/56563 ,  G01R33/56518 ,  G01R33/56554

Abstract: An RF pulse is applied to an object lying in an imaging region to which a static field is also applied. By applying a read-out gradient field to the object, gradient echoes are generated so that image reconstruction echo data are acquired. In addition to the image reconstruction echo data, two kinds of correction echo data are acquired at the same echo time but with the opposite read-out gradient field. These correction echo data have the same phase error component due to the inhomogeneity of the static field since the echo time is the same. These correction echo data have the opposite phase error component due to the eddy magnetic field in polarity. Therefore, a phase error caused by the eddy magnetic field can be corrected on the basis of these correction data.

Abstract translation: 将RF脉冲施加到也被施加静态场的成像区域中的对象。 通过对对象应用读出梯度字段，生成梯度回波，从而获取图像重构回波数据。 除了图像重建回波数据之外，在相同的回波时间处采用两种校正回波数据，但是具有相反的读出梯度场。 由于回波时间相同，这些校正回波数据由于静态场的不均匀性而具有相同的相位误差分量。 这些校正回波数据由于极性的涡流磁场而具有相反的相位误差分量。 因此，可以基于这些校正数据来校正由涡流磁场引起的相位误差。

公开(公告)号：US5729139A

公开(公告)日：1998-03-17

申请号：US603672

申请日：1996-02-20

Applicant: Takao Goto

Inventor： Takao Goto

IPC: G01R33/48 ,  A61B5/055 ,  G01R33/565 ,  G01V3/00

CPC classification number: G01R33/56527 ,  G01R33/56518 ,  G01R33/56563

Abstract: The present invention relates to an MRI apparatus capable of preventing the quality of an image from being degraded under the influence of eddy currents and residual magnetization caused by a phase encode gradient. While an RF pulse P1 is sent, a phase encode gradient gy(i) is applied to a warp axis and a read gradient rr is applied to a read axis, an NMR signal is received, followed by application of a rewind gradient gyr(i)' to the warp axis. The rewind gradient gyr(i)' is defined as "(a basic component of opposite polarity equal in time integral value to the phase encode gradient gy(i))+(a warp-axis correction component for correcting the influence of eddy currents or residual magnetization caused by the phase encode gradient gy(i))".

Abstract translation: 本发明涉及一种MRI装置，能够防止图像的质量在由相位编码梯度引起的涡电流和剩余磁化强度的影响下劣化。 当发送RF脉冲P1时，将相位编码梯度gy（i）施加到翘曲轴，读取梯度rr被施加到读取轴，接收NMR信号，随后应用倒带梯度gyr（i ）'到经轴。 反绕梯度gyr（i）'被定义为“（相位极性与相位编码梯度gy（i）的时间积分值相等的基本分量）+（用于校正涡流的影响的经向轴校正分量或 由相位编码梯度gy（i）引起的剩余磁化）“。

公开(公告)号：US5523689A

公开(公告)日：1996-06-04

申请号：US420213

申请日：1995-04-11

Applicant: Ralph Oppelt ,  Wilhelm Duerr

Inventor： Ralph Oppelt ,  Wilhelm Duerr

IPC: G01R33/20 ,  A61B5/055 ,  G01R33/34 ,  G01R33/36 ,  G01R33/422 ,  H01Q1/36 ,  G01V3/00

CPC classification number: G01R33/34046 ,  G01R33/34007 ,  G01R33/422 ,  G01R33/56518

Abstract: A radio-frequency antenna for a magnetic resonance apparatus has an antenna conductor in the form of a ribbon conductor. The ribbon antenna conductor has interconnects arranged side-by-side. Neighboring interconnects are connected to one another via bridges that conduct radio-frequency currents.

Abstract translation: 用于磁共振装置的射频天线具有带状导体形式的天线导体。 带状天线导体具有并排布置的互连。 相邻的互连通过传导射频电流的桥连接。

公开(公告)号：US5495171A

公开(公告)日：1996-02-27

申请号：US5296

申请日：1993-01-19

Applicant: Gordon T. Danby ,  John W. Jackson ,  Charles E. Brukl ,  Krishna M. Gudimetta ,  Joseph F. Rimkunas

Inventor： Gordon T. Danby ,  John W. Jackson ,  Charles E. Brukl ,  Krishna M. Gudimetta ,  Joseph F. Rimkunas

IPC: G01R33/36 ,  G01R33/383 ,  G01R33/421 ,  G01R33/565 ,  G01V3/00

CPC classification number: G01R33/4215 ,  G01R33/383 ,  G01R33/56518

Abstract: A primary field magnet assembly, of the type used in magnetic resonance imaging systems, which has been designed with the capability to suppress eddy currents during magnetic resonance imaging through the use of eddy current suppressing material. In addition, this invention includes the use of high conductivity material to decouple the imaging system radio frequency antennas from their environment, which generally includes the primary field magnet assembly, and can be used to preserve the signal-to-noise performance of the scanner. Such highly conductive material is effective when employed in combination with the primary field magnet assembly described herein.

公开(公告)号：US5015955A

公开(公告)日：1991-05-14

申请号：US456460

申请日：1989-12-26

Applicant: Ian R. Young

Inventor： Ian R. Young

IPC: A61B5/055 ,  G01R33/48 ,  G01R33/565

CPC classification number: G01R33/56518

Abstract: A method of reducing the effects of eddy currents produced by a gradient magnetic field pulse pattern applied to a body in a magnetic resonance method by selecting the rates of change of magnetic flux produced during the edges of the or each pulse of the pulse pattern in relation to the times elapsing between the edges and the time constants of the eddy currents.

公开(公告)号：US4724388A

公开(公告)日：1988-02-09

申请号：US869976

申请日：1986-06-02

Applicant: Koichi Sano ,  Tetsuo Yokoyama ,  Hideaki Koizumi

Inventor： Koichi Sano ,  Tetsuo Yokoyama ,  Hideaki Koizumi

IPC: G01R33/565 ,  G01R33/20

CPC classification number: G01R33/56518 ,  G01R33/56563

Abstract: In order to measure a static field distribution with one scanning operation and to make image distortion corrections with the static field distribution and a gradient field distribution simultaneously considered, an image is reconstructed using a spin echo signal produced under the condition that a time interval between a 90.degree. pulse and a 180.degree. pulse differs from an interval between the 180.degree. pulse and the time origin of the spin echo signal, the static field distribution is evaluated from the relation of distortions to phase errors free from a phase distortion attributed to the characteristic of a detecting part and a phase distortion attributed to the dynamic characteristic of the gradient field, a relations existing between the spatial distortion and phase distortion of the reconstructed image and a magnetic field distribution including the gradient field is obtained, and the distortion magnitude of the reconstructed image is evaluated from the measured magnetic field distribution.

Abstract translation: 为了通过一次扫描操作测量静态场分布，并且同时考虑静态场分布和梯度场分布进行图像失真校正，使用自旋回波信号来重构图像，该自旋回波信号是在 90°脉冲和180°脉冲与180°脉冲与自旋回波信号的时间原点之间的间隔不同，静态场分布从失真和相位误差的关系来评估，该相位误差不包括归因于特性的相位失真 得到归因于梯度场的动态特性的检测部分和相位失真，获得重建图像的空间失真和相位失真之间存在的关系以及包括梯度场的磁场分布，并且， 从测量的磁场分布评估重建图像 。