公开(公告)号：US5498963A

公开(公告)日：1996-03-12

申请号：US286365

申请日：1994-08-05

申请人： Erika Schneider ,  Xiguang Zang ,  Michael R. Hartley

发明人： Erika Schneider ,  Xiguang Zang ,  Michael R. Hartley

IPC分类号： G01R33/565 ,  G01V3/14

CPC分类号： G01R33/56518

摘要： In an MRI system NMR data is acquired and an image is reconstructed based on the net phase or phase difference of spins at locations in the imaged object. The phase or phase difference image is corrected for errors caused by non-linearities in one or more of the gradient fields. The phase or phase difference image values are weighted with spin signal magnitude image values and their locations warped to reflect gradient field non-linearity. The warped values are remapped to the image pixel locations and converted back to phase values by dividing by an average spin signal magnitude. In this manner geometric distortion caused by non-uniform magnetic field gradients are corrected without loss of quantitative phase or phase difference information.

摘要翻译： 在MRI系统中，获取NMR数据，并且基于成像对象中位置处的自旋的净相位或相位差重建图像。 针对由一个或多个梯度场中的非线性引起的误差来校正相位差或相位差图像。 相位或相位差图像值用自旋信号幅度图像值加权，并且它们的位置翘曲以反映梯度场非线性。 翘曲值被重新映射到图像像素位置，并通过除以平均自旋信号幅度而转换回相位值。 以这种方式，校正由不均匀磁场梯度引起的几何失真，而不损失定量相位或相位差信息。

公开(公告)号：US5999839A

公开(公告)日：1999-12-07

申请号：US16569

申请日：1998-01-30

申请人： Christopher Judson Hardy ,  Charles Lucian Dumoulin ,  Erika Schneider

发明人： Christopher Judson Hardy ,  Charles Lucian Dumoulin ,  Erika Schneider

IPC分类号： G01R33/48 ,  A61B5/055 ,  G01R33/28 ,  G01R33/485 ,  G01R33/563

CPC分类号： G01R33/563 ,  G01R33/281 ,  G01R33/485

摘要： A magnetic resonance (MR) imaging method uses chemical shift and/or slice selective inversion pulse to create angiograms of coronary arteries. In one embodiment blood is doped with a contrast enhancement agent and a sequence of slice selective and chemical shift selective inversion pulses are applied. Detection RF pulses then generate an image signal. In another embodiment two sequential chemical shift inversion pulses are applied followed by detection RF pulses for imaging.

摘要翻译： 磁共振（MR）成像方法使用化学位移和/或切片选择性反转脉冲来产生冠状动脉的血管造影。 在一个实施例中，血液掺杂有对比度增强剂，并且应用片选择和化学位移选择性反转脉冲序列。 检测RF脉冲然后产生图像信号。 在另一个实施例中，施加两个顺序的化学位移反转脉冲，随后检测用于成像的RF脉冲。

公开(公告)号：US5321359A

公开(公告)日：1994-06-14

申请号：US41305

申请日：1993-03-29

申请人： Erika Schneider

发明人： Erika Schneider

IPC分类号： G01R33/3875 ,  G01R33/54 ,  G01R33/565 ,  G01V3/00

CPC分类号： G01R33/4828 ,  G01R33/3875 ,  G01R33/56563

摘要： The harmonic relationship of certain chemical species is exploited to produce an MRI image of a single chemical species in the presence of at least two other chemical species with the acquisition of as few as two NMR images. If the chemical shift frequencies at a particular polarizing field strength can be approximated as the ratio of two odd integers, an evolution time can be chosen for the images acquired to cancel the contributions of two of the species in one image with a corresponding contribution in the other image. A image of the uncanceled species or of the cancelled species alone may be generated. A third image may be used to correct for inhomogeneities in the polarizing B.sub.0 field.

摘要翻译： 某些化学物质的谐波关系被利用以在存在至少两个其他化学物质的情况下产生单个化学物质的MRI图像，并且获取少至两个NMR图像。 如果特定偏振场强度下的化学位移频率可以近似为两个奇数整数的比值，则可以为获取的图像选择一个演化时间，以消除一个图像中两个物种的贡献，其中相应的贡献在 其他形象。 可能会产生未分类物种或被取消物种的图像。 可以使用第三个图像来校正极化B0场中的不均匀性。

公开(公告)号：US5168232A

公开(公告)日：1992-12-01

申请号：US546286

申请日：1990-06-29

申请人： Gary H. Glover ,  Erika Schneider

发明人： Gary H. Glover ,  Erika Schneider

IPC分类号： A61B5/055 ,  G01R33/20 ,  G01R33/24 ,  G01R33/38 ,  G01R33/387 ,  G01R33/3875

CPC分类号： G01R33/24 ,  G01R33/3875

摘要： Determination of the shimming fields for a polarizing NMR magnet is performed by acquiring two NMR images with evolution times differing by .tau.. A pixel by pixel division of the images yields a third image whose phase is proportional to magnetic field inhomogeneity. Several such inhomogeneity images are acquired within a cylindrical volume and the data of the images is fit according to a set of polynomials approximating the fields of the magnet shim coils. The coefficients of this fitting procedure are used to set the current level in the corresponding shim coils. The interaction between correction fields is accommodated by an empirically derived correction matrix. This procedure may be repeated to provide more accurate shimming.

公开(公告)号：US5711300A

公开(公告)日：1998-01-27

申请号：US515876

申请日：1995-08-16

申请人： Erika Schneider ,  Harvey Ellis Cline ,  Ronald Dean Watkins ,  Sheila Srinivasan Washburn ,  Christopher Judson Hardy

发明人： Erika Schneider ,  Harvey Ellis Cline ,  Ronald Dean Watkins ,  Sheila Srinivasan Washburn ,  Christopher Judson Hardy

IPC分类号： G01K7/36 ,  A61B5/055 ,  G01R33/48 ,  A61B8/00

CPC分类号： G01R33/4804

摘要： NMR images indicative of thermal changes in tissues undergoing therapy are produced using a gradient-recalled double-echo pulse sequence. A reference phase image is produced using a short echo time (TE.sub.1) and a measurement phase image is produced with a longer echo time (TE.sub.2). Temperature maps are produced during therapy using the phase difference information at corresponding pixels of the two phase images.

摘要翻译： 使用梯度回忆的双回波脉冲序列产生指示正在接受治疗的组织中热变化的NMR图像。 使用短回波时间（TE1）产生参考相位图像，并且以更长的回波时间（TE2）产生测量相位图像。 使用两相图像的相应像素处的相位差信息在治疗期间产生温度图。

公开(公告)号：US5617029A

公开(公告)日：1997-04-01

申请号：US572850

申请日：1995-12-14

申请人： Erika Schneider

发明人： Erika Schneider

IPC分类号： A61B5/055 ,  G01R33/3875 ,  G01V3/00

CPC分类号： G01R33/3875

摘要： A method is described which corrects magnetic field inhomogeneities in a magnetic resonance (MR) imaging system that takes into account the effects of a subject on the magnetic fields. A magnetic resonance sequence is applied to the subject to extract MR response signals from the subject indicating the magnetic field inhomogeneity over space. The changes of magnetic field inhomogeneity with a change in radial variable .rho. (or r, in a cylindrical coordinate system) are calculated. A derivative with respect to a radial variable is calculated of a generalized 3D infinite series polynomial, such as a Legendre polynomial expressed in spherical coordinates. These inhomogeneity changes are then fit to 3D polynomial derivative to result in coefficients [dI.sub.c ]. Similarly coefficients of a derivative shim coil calibration matrix [dM] are determined for each shim coil modeling the effect of each shim coil is on the magnetic field within the imaging volume. An inverse derivative matrix [dM] is calculated to result in the inverse derivative matrix [dM.sup.-1 ]. The inverse derivative matrix [dM.sup.-1 ] is multiplied by the coefficients [dI.sub.c ] to determine current coefficients [C] which define currents to be passed through each shim coil to correct the magnetic field inhomogeneities.

摘要翻译： 描述了一种校正磁共振（MR）成像系统中考虑到对象对磁场的影响的磁场不均匀性的方法。 向对象施加磁共振序列以从对象提取表明在空间上的磁场不均匀性的MR响应信号。 计算出径向变量rho（或圆柱坐标系中的r）变化的磁场不均匀性的变化。 通过广义3D无限序列多项式计算相对于径向变量的导数，如用球面坐标表示的勒让德多项式。 然后将这些不均匀性变化拟合为3D多项式导数，得到系数[dIc]。 类似地，对于每个垫片线圈确定导数垫片线圈校准矩阵[dM]的系数，模拟每个垫片线圈对成像体积内的磁场的影响。 计算逆导数矩阵[dM]，得到逆导数矩阵[dM-1]。 逆导数矩阵[dM-1]乘以系数[dIc]，以确定限定要通过每个垫片线圈的电流的电流系数[C]，以校正磁场不均匀性。

公开(公告)号：US5671742A

公开(公告)日：1997-09-30

申请号：US772648

申请日：1996-12-23

申请人： Charles Lucian Dumoulin ,  Erika Schneider

发明人： Charles Lucian Dumoulin ,  Erika Schneider

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

CPC分类号： G01R33/5635 ,  G01R33/56308

摘要： Radiofrequency (RF) and magnetic field gradient pulse sequences employ Time-of-Flight (TOF) strategy to selectively create transverse spin magnetization which is then maintained for a selected period of time and then imaged in order to generate a vessel selective magnetic resonance angiogram. The pulse sequence employs a spatially selective excitation pulse which is used to create transverse spin magnetization in a selected region of a subject. This region typically is made to include the root of the vessel to be imaged. After excitation, transverse magnetization is maintained with a series of refocusing RF pulses while the blood moves along the vessel. The transverse magnetization is then sampled at one or more selected times after excitation with conventional imaging strategies.

摘要翻译： 射频（RF）和磁场梯度脉冲序列使用飞行时间（TOF）策略来选择性地产生横向自旋磁化，然后将其保持选定的时间段，然后成像以产生血管选择性磁共振血管造影。 脉冲序列采用空间选择性激发脉冲，其用于在受试者的选定区域中产生横向自旋磁化。 该区域通常被制成包括待成像的血管的根部。 激发后，当血液沿着血管移动时，横向磁化通过一系列重新聚焦RF脉冲保持。 然后在用常规成像策略激发之后的一个或多个选定时间对横向磁化进行取样。

公开(公告)号：US5545995A

公开(公告)日：1996-08-13

申请号：US346599

申请日：1994-11-29

申请人： Erika Schneider ,  Anton M. Linz ,  Gregory A. Repinski

发明人： Erika Schneider ,  Anton M. Linz ,  Gregory A. Repinski

IPC分类号： G01R33/565 ,  G01R33/20

CPC分类号： G01R33/56563 ,  G01R33/56518

摘要： A calibration procedure for correcting geometric errors in MRI images due to gradient field non-linearities and magnetic field inhomogeneities includes performing a 3D scan on a calibration phantom. The calibration phantom contains an array of tapered rods that produce an array of spots in reconstructed slice images. Spot sizes and positions enable position errors to be measured throughout the bore of the imaging system. Corrective coefficients are produced from these 3D error measurements that enable subsequent patient images to be corrected for warping errors in object position.

摘要翻译： 用于校正由于梯度场非线性和磁场不均匀性引起的MRI图像中的几何误差的校准过程包括在校准体模上执行3D扫描。 校准模型包含一系列锥形棒，其在重建的切片图像中产生点阵列。 斑点尺寸和位置使得能够在成像系统的整个孔内测量位置误差。 通过这些3D误差测量产生校正系数，使得随后的患者图像能够在物体位置纠正错误。

公开(公告)号：US5225781A

公开(公告)日：1993-07-06

申请号：US717966

申请日：1991-06-20

申请人： Gary H. Glover ,  Erika Schneider

发明人： Gary H. Glover ,  Erika Schneider

IPC分类号： G01R33/485 ,  G01R33/54

CPC分类号： G01R33/4828 ,  G01R33/485

摘要： A method of separating fat and water proton NMR images in the presence of local magnetic field inhomogeneities uses multiple images with phase shift between the water and fat signals. The phase shifts need not be multiples of .pi. and are selected so that at least two images are not "fat opposed" and so that images are not symmetric in phase shift around a "fat aligned" image. A switch function is developed from the argument of the combined images to unambiguously identify the predominant chemical species of each voxel. Wrap arounds in the argument resulting from the limited range of trigonometric functions are treated first by subtracting a low order polynomial, then detecting and removing wrap around discontinuities.

摘要翻译： 在存在局部磁场不均匀性的情况下分离脂肪和水质子NMR图像的方法使用具有水和脂肪信号之间的相移的多个图像。 相移不需要是pi的倍数，并且被选择为使得至少两个图像不是“胖对比”，并且使得图像在“胖对准”图像周围的相移中不对称。 从组合图像的论证中开发了一个开关功能，以明确地识别每个体素的主要化学物种。 首先通过减去低阶多项式，然后检测和去除包围不连续性来处理由三角函数范围有限引起的论证中的包围。

公开(公告)号：US4987371A

公开(公告)日：1991-01-22

申请号：US441850

申请日：1989-11-27

申请人： Gary H. Glover ,  Erika Schneider

发明人： Gary H. Glover ,  Erika Schneider

IPC分类号： A61B5/055 ,  G01R33/24 ,  G01R33/387 ,  G01R33/3875

CPC分类号： G01R33/3875 ,  G01R33/24

摘要： In-vivo shimming is performed by acquiring two NMR images with evolution times differing by ##EQU1## where .omega..sub.1, .omega..sub.2, are the Larmor frequencies of the dominant proton species of the imaged object. A pixel by pixel division of the image yields a third image whose phase is proportional to magnetic field inhomogeneity. The phase of the third image set has periodic discontinuities as a result of the periodicity of the arctangent function used to extract the phase from the image. These discontinuities are removed by taking the derivative of the phase and integrating the product of that derivative and a weighting function where the weighting function has zero weight at the points of discontinuity. Off-center quadratic terms in the inhomogeneity are removed prior to fitting the linear shimming gradients.