公开(公告)号：US4742301A

公开(公告)日：1988-05-03

申请号：US871010

申请日：1986-06-05

申请人： Peter van der Meulen ,  Johannes P. Groen ,  Johannes J. M. Cuppen

发明人： Peter van der Meulen ,  Johannes P. Groen ,  Johannes J. M. Cuppen

IPC分类号： G01R33/54 ,  G01R33/56 ,  G01R33/561 ,  G01N24/08

CPC分类号： G01R33/482 ,  G01R33/56 ,  G01R33/5613

摘要： In known spin echo imaging examination a waiting period is customarily observed between two successive spin echo measurements in order to allow for the magnetic moment to relax in the direction of the uniform magnetic field Bo. In addition to this waiting period, the use of 180.degree. pulses also leads to a comparatively long examination time which increases the risk of image artefacts due to motions of, for example a patient to be examined. This comparatively long examination time is also unfavorable in view of the radiation load. In order to avoid these drawbacks, a method is proposed in which the electromagnetic pulses used are exclusively excitation pulses in the form of .alpha..degree. pulses, where 0

公开(公告)号：US5455512A

公开(公告)日：1995-10-03

申请号：US143268

申请日：1993-10-26

申请人： Johannes P. Groen ,  Peter Van Der Meulen ,  Gerrit H. Van Yperen ,  Antoon F. Mehlkopf

发明人： Johannes P. Groen ,  Peter Van Der Meulen ,  Gerrit H. Van Yperen ,  Antoon F. Mehlkopf

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

CPC分类号： G01R33/56518

摘要： In an MRI device operating according to a spin-echo method, switched gradient magnetic fields are applied in the form of slice selection, phase encoding and read gradients. The switching of the gradients causes eddy currents in metal parts of the apparatus. The eddy currents disturb the applied magnetic fields, thereby changing the phases of the precessing nuclear spins of a body to be examined and causing artefacts in a reconstructed image. The disturbing effects of the eddy currents is compensated for by supplementing a sequence of switched gradient magnetic fields with additional gradient fields. These additional fields have zero net effect but induce further eddy currents which compensate for the disturbing effects of the eddy currents generated by the regular switched gradient magnetic fields. The additional gradient fields are chosen such that the total time-integrated strength of a gradient in any interval between two RF-pulses is substantially equal to the desired value.

摘要翻译： 在根据自旋回波方法操作的MRI装置中，以切片选择，相位编码和读取梯度的形式施加开关梯度磁场。 梯度的切换在设备的金属部分引起涡流。 涡流干扰所施加的磁场，从而改变要检查的身体的进动核自旋的相位，并在重建的图像中引起伪影。 通过用附加梯度场补充一系列切换梯度磁场来补偿涡流的干扰效应。 这些附加场具有零净效应，但是引起进一步的涡流，其补偿由常规开关梯度磁场产生的涡流的干扰效应。 选择附加的梯度场，使得两个RF脉冲之间的任何间隔中的梯度的总时间积分强度基本上等于期望值。

公开(公告)号：US4707660A

公开(公告)日：1987-11-17

申请号：US768400

申请日：1985-08-22

申请人： Johannes J. M. Cuppen ,  Johannes P. Groen

发明人： Johannes J. M. Cuppen ,  Johannes P. Groen

IPC分类号： A61B10/00 ,  A61B5/055 ,  G01N24/08 ,  G01R33/48 ,  G01R33/561 ,  G01R33/20

CPC分类号： G01N24/08 ,  G01R33/561 ,  G01R33/5615 ,  G01R33/5616

摘要： The invention relates to the determination of an NMR distribution in which an alternating gradient field is applied while sampling the NMR signal (FID signal, nuclear spin echo signal). The frequency of the alternating gradient field is comparatively low (order of magnitude of 100 Hz) and the field has from a few to some tens of cycles during each measurement period. While an FID signal is being sampled, the image frequency field matrix is scanned using a zig-zag (oscillating) line pattern during each line when data is provided for elements in from a few to some tens of rows in the image frequency matrix. By applying preparation gradient fields, the image frequency matrix can be filled by means of successive zig-zag line patterns which have been shifted with respect to one another and which thus enable a uniform sampling density to be provided in the image frequency space. The filling of the image frequency matrix with signal samples is thus speeded up by a factor of a few to some tens of times by the invention, the energy required for controlling the gradient field coils being substantially reduced at the same time.

摘要翻译： 本发明涉及在对NMR信号（FID信号，核自旋回波信号）采样时施加交替梯度场的NMR分布的确定。 交变梯度场的频率相对较低（数量级为100Hz），并且在每个测量周期期间该场具有从几个到几十个周期。 当对FID信号进行采样时，在图像频率矩阵中为数字到几十行的元素提供数据时，在每行期间使用锯齿形（振荡）线图案扫描图像频率场矩阵。 通过应用准备梯度场，图像频率矩阵可以通过已经相对于彼此移位的连续的之字形线图案来填充，并且因此能够在图像频率空间中提供均匀的采样密度。 通过本发明，图像频率矩阵与信号样本的填充因此被加速了几到几十倍，控制梯度场线圈所需的能量同时显着减少。

公开(公告)号：US4754223A

公开(公告)日：1988-06-28

申请号：US921929

申请日：1986-10-20

申请人： Josephus J. E. In Den Kleef ,  Johannes P. Groen

发明人： Josephus J. E. In Den Kleef ,  Johannes P. Groen

IPC分类号： A61B10/00 ,  A61B5/055 ,  G01R33/48 ,  G01R33/54 ,  G01R33/565 ,  G01R33/20

CPC分类号： G01R33/482 ,  G01R33/56518

摘要： During known MRI measurements, for example spin echo and inversion recovery measurements, phase errors occur in pixels, inter alia due to eddy currents caused by the application or interruption of magnetic field gradients during a measurement. There is proposed an inversion recovery method combined with a method where the magnetization is not inverted in advance in order to determine for each pixel the phase error in an image obtained by means of an inversion recovery method, so that inversion recovery images can be obtained which do not contain phase errors.

摘要翻译： 在已知的MRI测量期间，例如自旋回波和反演恢复测量，相位误差发生在像素中，特别是由于应用引起的涡流或测量期间磁场梯度的中断。 提出了一种与预先不反转磁化的方法组合的反转恢复方法，以便为每个像素确定通过反转恢复方法获得的图像中的相位误差，从而可以获得反转恢复图像，其中， 不包含相位误差。

公开(公告)号：US5951472A

公开(公告)日：1999-09-14

申请号：US960249

申请日：1997-10-29

申请人： Johannes J. Van Vaals ,  Johannes P. Groen

发明人： Johannes J. Van Vaals ,  Johannes P. Groen

IPC分类号： G01R33/28 ,  G01R33/561 ,  G01R33/567 ,  A61B5/055

CPC分类号： G01R33/285 ,  G01R33/56308

摘要： An MR system for interventional procedures, includes an MR device and an invasive device. The MR device is arranged to acquire images of a part of an object. A part of the invasive device can be imaged in an MR image by providing a coil or a conductor loop which has two non-magnetic conductors which are situated at some distance from one another underneath the surface of the invasive device. A reduction of artefacts due to the movement of a patient or the invasive device can be obtained by sampling an MR signal, whereby an auxiliary magnetic field is periodically applied during the time in which the plurality of lines in k-space are scanned.

摘要翻译： 用于介入程序的MR系统包括MR装置和侵入性装置。 MR装置被布置成获取对象的一部分的图像。 侵入性装置的一部分可以通过提供线圈或导体环来成像在MR图像中，所述线圈或导体环具有两个非侵入性导体，该非磁性导体位于与入侵装置的表面下方相距一定距离处。 可以通过对MR信号进行采样来获得由于患者或侵入性装置的移动引起的人为因素的减少，从而在扫描k空间中的多个行的时间期间周期性地施加辅助磁场。

公开(公告)号：US4870361A

公开(公告)日：1989-09-26

申请号：US211727

申请日：1988-06-27

申请人： Josephus J. E. In Den Kleef ,  Johannes P. Groen ,  Rudolf G. De Graaf

发明人： Josephus J. E. In Den Kleef ,  Johannes P. Groen ,  Rudolf G. De Graaf

IPC分类号： A61B5/0265 ,  A61B5/055 ,  A61B10/00 ,  G01R33/44 ,  G01R33/48 ,  G01R33/54 ,  G01R33/563 ,  G01R33/565

CPC分类号： G01R33/563 ,  G01R33/56518

摘要： An MR angiography method in which an angiogram is formed from the difference between amplitude and/or phase information contained in first and second complex images produced by different gradient waveforms in respective first and second types of excitation sequences. The gradient waveforms are chosen so that in the angiogram obtained from the first and second complex images, ideally, signals orginating from excited stationary spin nuclei are not present while the signals orginating from moving spin nuclei, due to flow in blood vessels, are present. However, stationary spin nuclei can be somewhat differently excited in the first and second sequence due to the different gradient waveforms used which cause different eddy currents to flow in metal parts of the apparatus. In the absence of correction, these eddy currents would exert their influence magnetically by causing a smoothly varying phase error in the difference between the first and second complex images resulting in erroneous signal contribution to the angiogram from stationary spin nuclei. This erroneous signal is eliminated by estimating the smoothly varying phase difference before forming the angiogram from the first and second complex images and by thus carrying out a non-linear phase correction.

公开(公告)号：US06172502B2

公开(公告)日：2001-01-09

申请号：US09029531

申请日：1998-02-27

申请人： Johannes P. Groen ,  Arianne M. C. Van Muiswinkel ,  Gerald Van Ensbergen

发明人： Johannes P. Groen ,  Arianne M. C. Van Muiswinkel ,  Gerald Van Ensbergen

IPC分类号： G01V300

CPC分类号： G01R33/56554

摘要： According to the known method, a reference measurement is performed by measurement of magnetic resonance signals, without application of a magnetic gradient field to introduce phase encoding in the magnetic resonance signals. According to the invention, two measurements are performed with a read-out gradient of opposite polarity at substantially corresponding instants, relative to an instant at which the contributions to the phase error due to frequency deviations are zero. The advantage of the novel method resides in the fact that a higher insensitivity to field inhomogeneities and chemical shifts is achieved.

摘要翻译： 根据已知的方法，通过测量磁共振信号来执行参考测量，而不施加磁梯度场以在磁共振信号中引入相位编码。 根据本发明，相对于对由于频率偏差引起的相位误差的贡献为零的瞬间，在基本相应的时刻以相反极性的读出梯度执行两次测量。 该方法的优点在于实现了对场不均匀性和化学位移的更高的不敏感性。

公开(公告)号：US5647362A

公开(公告)日：1997-07-15

申请号：US306095

申请日：1994-09-14

申请人： Miha Fuderer ,  Johannes P. Groen

发明人： Miha Fuderer ,  Johannes P. Groen

IPC分类号： A61B5/055 ,  G01R33/54 ,  G01R33/561

CPC分类号： G01R33/56554

摘要： In an EPI or GRASE magnetic resonance method, phase errors caused by the alternation of the read gradient polarity (G.sub.x) are corrected by obtaining a set of reference measurements with both polarities at low values in the phase encoding (k.sub.y) direction. From these reference measurements the phase errors are estimated. Subsequently, the measurements covering the whole of k-space are corrected and a magnetic resonance image obtained in which artefacts due to the alternating polarity of the read gradient are suppressed.

摘要翻译： 在EPI或GRASE磁共振方法中，通过在相位编码（ky）方向上获得具有低值的两个极性的参考测量集合来校正由读取梯度极性（Gx）的交替引起的相位误差。 从这些参考测量中，估计相位误差。 随后，校正覆盖整个k空间的测量，并且抑制由于读取梯度的交替极性而导致的伪像的获得的磁共振图像。

公开(公告)号：US5810727A

公开(公告)日：1998-09-22

申请号：US819229

申请日：1997-03-17

申请人： Johannes P. Groen

发明人： Johannes P. Groen

IPC分类号： G01R33/20 ,  A61B5/055 ,  G01R33/48 ,  G01R33/561 ,  G01R33/563 ,  A61B5/05

CPC分类号： G01R33/56308 ,  G01R33/5616 ,  G01R33/56316

摘要： In a magnetic resonance method for imaging a part of a body which is arranged in a steady magnetic field, magnetic resonance signals are measured utilizing an initial read gradient and an alternating read gradient. The method can be used, for example for phase contrast angiography and for flow velocity measurements in a body of a patient. In order to counteract artifacts in the image due to inhomogeneities of the steady magnetic field, the time elapsing between an excitation RF pulse exciting spins in the part of the body and the initial read gradient is varied in successive pulse sequences. However, this causes artifacts in the fluid flow images due to the phase error which itself is caused by the spins flowing in the direction of the gradient field. In order to counteract these artifacts, the first-order moment of the initial read gradient and a first order lobe of the alternating read gradient is kept substantially constant in each pulse sequence.

摘要翻译： 在用于对被布置在稳定磁场中的身体的一部分进行成像的磁共振方法中，使用初始读取梯度和交替读取梯度来测量磁共振信号。 可以使用该方法，例如用于相位对比血管造影术和用于患者体内的流速测量。 为了抵消由于稳定磁场的不均匀性造成的图像中的伪影，在身体部分的激发RF脉冲激励旋转与初始读取梯度之间经过的时间在连续的脉冲序列中变化。 然而，这由于相位误差而导致流体流动图像中的伪像，其本身是由沿着梯度场的方向流动的自旋引起的。 为了抵消这些伪影，在每个脉冲序列中，初始读取梯度的一阶矩和交替读取梯度的第一级波瓣保持基本上恒定。