公开(公告)号：US4862081A

公开(公告)日：1989-08-29

申请号：US275392

申请日：1988-11-23

申请人： Kenneth S. Denison

发明人： Kenneth S. Denison

IPC分类号： A61B5/055 ,  G01R33/48 ,  G01R33/56 ,  G01R33/565

CPC分类号： G01R33/565 ,  G01R33/56 ,  G01R33/3621

摘要： In the absence of signals supplied to gradient field coils (14), radio frequency signals, or magnetic resonance signals received by coil (18), analog-to-digital converters (44, 46) indicate background noise and DC offset. An attenuator (26) attenuates signals from the receiving coil in the absence of magnetic resonance signals. A phase sensitive detector (38) produces real and imaginary signal components both in the absence of magnetic resonance signals during calibration and subsequently during the processing of magnetic resonance signals. The analog-to-digital converters, low pass filters (40, 42), and the phase sensitive detectors inject an undesirable DC offset into the signals. In the absence of a magnetic resonance signal, the digitized output of the analog-to-digital converters is substantially the DC offset plus noise. A statistical analysis routine (64) analyzes the sampled analog-to-digital data in the absence of a magnetic resonance signal. Based on the variation among the samples, the desired level of confidence and accuracy, the statistical analysis means determines how many samples must be averaged to determine the DC noise with the desired confidence. An averaging circuit (66) averages at least the selected number of samplings. DC correction circuits (50, 52) subtract the determined DC offset values for the real and imaginary channels from the real and imaginary magnetic resonance signals in subsequent scans before the magnetic resonance data is reconstructed (54) into an image representations.

摘要翻译： 在没有提供给梯度场线圈（14）的信号的情况下，由线圈（18）接收的射频信号或磁共振信号，模拟 - 数字转换器（44,46）表示背景噪声和DC偏移。 在没有磁共振信号的情况下，衰减器（26）衰减来自接收线圈的信号。 相位敏感检测器（38）在校准期间并且随后在磁共振信号的处理期间在没有磁共振信号的情况下产生实部和虚部信号分量。 模数转换器，低通滤波器（40,42）和相敏检测器将不期望的直流偏移注入到信号中。 在没有磁共振信号的情况下，模数转换器的数字化输出基本上是直流偏移加噪声。 统计分析程序（64）在没有磁共振信号的情况下分析采样的模拟数字数据。 基于样本之间的变化，所需的置信度和精度水平，统计分析装置确定必须平均多少样本以确定具有期望置信度的DC噪声。 平均电路（66）至少平均选择的采样数量。 直流校正电路（50,52）在将磁共振数据重建（54）之前的后续扫描中从真实和虚拟磁共振信号中减去确定的实信号和虚信号的DC偏移值（54）。

公开(公告)号：US5073752A

公开(公告)日：1991-12-17

申请号：US510981

申请日：1990-04-19

申请人： Gordon D. DeMeester ,  Kenneth S. Denison ,  Francis H. Bearden

发明人： Gordon D. DeMeester ,  Kenneth S. Denison ,  Francis H. Bearden

IPC分类号： A61B5/055 ,  G01R33/48 ,  G01R33/54 ,  G01R33/56 ,  G06F17/14 ,  G06T1/00

CPC分类号： G01R33/56

摘要： Magnetic resonance imaging data lines or views are generated and stored in a magnetic resonance data memory (56). The number of views or phase encode gradient steps N along each of one or more phase encode gradient directions is selected (70) to match the dimensions of the region of interest. A discrete Fourier transform algorithm (94) operates on the data in the magnetic resonance data memory to generate an image representation for storage in an image memory (96). Unlike a fast Fourier transform algorithm which requires a.sup.N views or data lines, where a and N are integers, the discrete Fourier transform has a flexible number of data lines and data values which can be accommodated. More specifically to the preferred embodiment, the discrete Fourier transform operation is performed by a CHIRP-Z transform or a Goertzel's second order Z-transform which can accommodate any number of data lines or values.

公开(公告)号：US4881033A

公开(公告)日：1989-11-14

申请号：US331750

申请日：1989-04-03

申请人： Kenneth S. Denison ,  G. Neil Holland ,  Gordon D. DeMeester

发明人： Kenneth S. Denison ,  G. Neil Holland ,  Gordon D. DeMeester

IPC分类号： G01R33/50 ,  G01R33/56

CPC分类号： G01R33/5602 ,  G01R33/482 ,  G01R33/5608 ,  G01R33/56554

摘要： A multi-echo magnetic resonance imaging sequence is implemented such that a radio frequency receiver (34) receives magnetic resonance signals during each of a plurality of magnetic resonance echoes. The resonance data received during each echo are digitized and the resultant echo data are stored in a corresponding echo memory (40, 42). The locations of the data within the memories are brought into registration (52) such that corresponding data in each memory is disposed at the same memory address. Because data from later echoes tends to be weaker or at a lower magnitude, the magnitude of the data stored in each memory is normalized (60). The phase of the data in each memory is brought into coordination by a zero order phase correction (70). A high pass filter (84) and a complementary low pass filter (86) separate complementary portions of the data from the memories. The separated portions are combined into a single synthesizied data set for storage in memory (82). The syntheized data are Fourier transformed (100) to produce a synthetic image which has selected characteristics of an early echo image, e.g. high resolution, and selected characteristics of a late echo image, e.g. good T2 contrast. In this manner, the synthetic image has properties or characteristics which render it more diagnostically valuable than either an early or late echo image.

摘要翻译： 实现多回波磁共振成像序列，使得射频接收器（34）在多个磁共振回波中的每一个期间接收磁共振信号。 在每个回波期间接收到的共振数据被数字化，并且所得到的回波数据被存储在对应的回波存储器（40,42）中。 将存储器内的数据的位置进行注册（52），使得每个存储器中的对应数据被布置在相同的存储器地址处。 因为来自后期回波的数据趋向于较弱或处于较低幅度，所以存储在每个存储器中的数据的幅度被归一化（60）。 通过零阶相位校正（70）使每个存储器中的数据的相位协调。 高通滤波器（84）和互补低通滤波器（86）将数据与存储器的互补部分分开。 分离的部分被组合成单个合成的数据集合以存储在存储器（82）中。 合成数据经傅里叶变换（100）以产生合成图像，该合成图像选择早期回波图像的特征，例如， 高分辨率和晚期回波图像的选定特征，例如。 良好的T2对比度。 以这种方式，合成图像具有使其比早期或晚期回波图像更具诊断价值的性质或特征。

公开(公告)号：US4761819A

公开(公告)日：1988-08-02

申请号：US19567

申请日：1987-02-27

申请人： Kenneth S. Denison ,  William Sattin

发明人： Kenneth S. Denison ,  William Sattin

IPC分类号： G01N23/04 ,  A61B5/055 ,  A61B6/00 ,  A61B6/03 ,  A61B10/00 ,  G01R33/28 ,  G01R33/32 ,  G06K9/40 ,  G06T1/00 ,  G06T5/00 ,  G06T5/20 ,  H04N1/405 ,  H04N1/407 ,  H04N1/409

CPC分类号： G06K9/40 ,  G06T5/20

摘要： An MRI or other scanner (A) generates medical diagnostic data d(x,y) which has a Gaussian noise distribution for reconstruction by an imager (B) into an electronic image representation P(i,j) which may have a Gaussian or Rayleigh noise distribution. An image improving circuit (C) replaces each image pixel value P(i,j) from an image reconstruction means (32) with an improved pixel value P*(i,j) defined as follows:P*(i,j)=G(i,j)[P(i,j)-P(i,j)]+P(i,j)-n,where G(i,j) is a weighting function uniquely defined for each pixel (i,j), P is the mean of pixel values of neighboring pixels and n is the mean image noise. The weighting function is based on a diagnostic data noise variance and a pixel value variance V(i,j) corresponding to the same pixel. The data noise variance is derived by comparing a data value difference between each data value d(x,y) and its neighboring data values in a data memory (30). The smallest data value difference is indicative of the image noise variance. Each pixel variance is indicative of the difference between a corresponding pixel value and the neighboring pixel values. Preferably, the weighting function is: ##EQU1## For a Gaussian image noise distribution: V(noise)=.sigma.g.sup.2n=0.For a Rayleigh image noise distribution:V(noise)=(2-.pi./2).sigma.g.sup.2n=(.pi./2).sup.1/2 .sigma.g

公开(公告)号：US5170123A

公开(公告)日：1992-12-08

申请号：US392649

申请日：1989-08-11

申请人： G. Neil Holland ,  Douglas M. Blakeley ,  John R. Stauber ,  David C. Flugan ,  Kenneth S. Denison

发明人： G. Neil Holland ,  Douglas M. Blakeley ,  John R. Stauber ,  David C. Flugan ,  Kenneth S. Denison

IPC分类号： A61B5/055 ,  G01R33/36 ,  G01R33/48

CPC分类号： G01R33/3607

摘要： A magnetic resonance imaging apparatus includes one or more digital transmitters (B), one or more digital receivers (C), and digital data processing circuitry (D) which are all clocked and controlled by a single clock (F). Each digital transmitter includes a numerically controlled modulated oscillator (20) which processes digital phase and frequency signals to produce an output which addresses a wave-form map stored in a PROM (22). Each wave-form output of the PROM is multiplied (24) by a digital amplitude profile signal to generate a phase, frequency, and amplitude modulated digital RF signals. A clock gate (30) controls clocking of the digital modulation to create RF pulses. A digital-to-analog converter (28) converts the digital information to an analog RF pulse which is applied to a subject in an image region. The receivers each include an analog-to-digital converter (60) which digitizes the magnetic resonance signal emanating from the subject in the image region with four fold oversampling. A pair of FIR filters (62a, 62b) multiply the digital resonance signal by digital sine and cosine filter coefficients to create in-phase and out-of-phase digital magnetic resonance signal components. After additional digital filtering (64a, 64b), the digital in-phase and quadrature components are Fourier transformed (70) and accumulated in an image memory (72) to form an image representation.

公开(公告)号：US5124649A

公开(公告)日：1992-06-23

申请号：US56817

申请日：1987-06-02

申请人： Kenneth S. Denison ,  G. Neil Holland

发明人： Kenneth S. Denison ,  G. Neil Holland

IPC分类号： G01R33/56 ,  G01R33/561 ,  G01R33/567

CPC分类号： G01R33/56509 ,  G01R33/56 ,  G01R33/5619

摘要： A gradient magnetic field control (20) and a transmitter (30) are operated under the control of a timing and control computer (40) to generate magnetic resonance excitation pulse sequences. Each sequence provides phase encoding with one of a plurality of phase angles to the resultant resonance signals. A receiver (34) receives the phase encoded magnetic resonance signals which are digitized by an analog to digital converter (50) to form a plurality of views which are stored in a view memory (52). A larger plurality of views are generated adjacent a central or zero phase angle, e.g. views -63 to +64 of FIG. 2, and only one or a smaller plurality of views are generated adjacent peripheral phase angles, e.g. views -127 to -64 and +65 to +128 of FIG. 2. The slower, low frequency motion artifacts, such as respiratory motion artifacts, manifest themselves in the low frequency phase encoded views adjacent the zero phase encode angle. Averaging a plurality of views encoded adjacent the zero phase angle attenuates low frequency motion artifacts. The high frequency views adjacent the .+-.90.degree. phase angles contribute little or nothing to the low frequency motion artifacts. Accordingly, the high frequency views are either uniquely collected or a smaller number are averaged.

摘要翻译： 梯度磁场控制（20）和发射器（30）在定时和控制计算机（40）的控制下操作以产生磁共振激励脉冲序列。 每个序列提供相对于所得到的共振信号的多个相位角之一的相位编码。 接收器（34）接收由模拟数字转换器（50）数字化的相位编码的磁共振信号，以形成存储在视图存储器（52）中的多个视图。 在中心或零相位角附近产生较大的多个视图，例如， 视图-63至+64。 如图2所示，并且仅邻近外围相位角产生仅一个或更小的多个视图。 视图-127到-64和+65到+128的图。 较慢的低频运动假象，例如呼吸运动伪像，表现在与零相位编码角相邻的低频相位编码视图。 将邻近零相位角编码的多个视图平均衰减低频运动伪像。 与+/- 90°相位角相邻的高频视图对低频运动伪像贡献很小或没有。 因此，高频视图被唯一地收集或者较小的数目被平均。

公开(公告)号：US4833407A

公开(公告)日：1989-05-23

申请号：US124040

申请日：1987-11-23

申请人： G. Neil Holland ,  Terrence J. Provost ,  Gordon D. DeMeester ,  Kenneth S. Denison

发明人： G. Neil Holland ,  Terrence J. Provost ,  Gordon D. DeMeester ,  Kenneth S. Denison

IPC分类号： A61B10/00 ,  A61B5/055 ,  G01R33/44 ,  G01R33/48 ,  G01R33/50 ,  G01R33/54 ,  G01R33/56 ,  G01R33/561

CPC分类号： G01R33/56 ,  G01R33/561 ,  G01R33/5602

摘要： A spin echo (52) and a gradient echo (60) are generated in each magnetic resonance sequence repetition. The spin echo is phase encoded by a phase encode gradient (44) in regular steps spanning about a quarter of k-space. More particularly, steps from -n to G.sub.max /2, where n is a small integer and G.sub.max is the maximum phase encode gradient. An off-set phase encode gradient (58) shifts the phase encoding of the gradient echo by G.sub.max /2 relative to the first phase encoding gradient. Data to fill the empty portions of k-space (142, 167) between -n and -G.sub.max are generated from the complex conjugate (140, 160), of the first echo data (74) and the second echo data (76). The first and second echo data and the complex conjugate data are transformed (122, 132, 146, 166) to generate parted image representations (124, 134, 148, 168). The first echo image representation and the corresponding conjugately symmetric image representation are phase corrected (126, 150) in accordance with a phase map ( 112) derived from the central most first echo data (78). The partial image representations are summed (170) to produce a resultant image representation (172).

摘要翻译： 在每个磁共振序列重复中产生自旋回波（52）和梯度回波（60）。 自旋回波由相位编码梯度（44）进行相位编码，其规则步长约为四分之一的k空间。 更具体地，从-n到Gmax / 2的步骤，其中n是小整数，Gmax是最大相位编码梯度。 偏移相位编码梯度（58）相对于第一相位编码梯度将梯度回波的相位编码移位Gmax / 2。 从第一回波数据（74）和第二回波数据（76）的复共轭（140,160）生成-n和-Gmax之间的填充k空间（142,167）的空部分的数据。 第一和第二回波数据和复共轭数据被变换（122,132,146,166）以产生分离的图像表示（124,134,148,168）。 根据从中央最初回波数据（78）得到的相位图（112），第一回波图像表示和对应的共同对称图像表示被相位校正（126,150）。 将部分图像表示相加（170）以产生所得到的图像表示（172）。