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公开(公告)号：US5481192A
公开(公告)日：1996-01-02
申请号：US150655
申请日：1993-11-10
IPC分类号： A61B5/055 , G01R33/385 , G01V3/00
CPC分类号： G01R33/3854 , G01R33/3852
摘要： A magnetic resonance apparatus includes a magnet system (1) for generating a steady magnetic field in a measuring space (35), a gradient coil system (3) for generating gradient fields in the measuring space, and a power supply source (7) for the gradient coils (3) which comprises at least one gradient signal generator (9) and a number of gradient amplifiers (11), each of which is connected between an output of the gradient signal generator and at least one of the gradient coils. In order to cancel annoying noise caused by the gradient coils (3), the apparatus also includes a noise cancellation device which includes the following elements:a) a first filter device (39) having a number of inputs which corresponds to the number of gradient amplifiers (11), each of the inputs being connected to an output of the gradient signal generator (9), and also includes a corresponding number of outputs, the first filter device having transfer functions, all of which correspond approximately to the transfer function of one of the chains extending from the gradient signal generator (9), via one of the gradient amplifiers (11), the gradient coil (coils) (3) connected to this gradient amplifier, and air, to a region (40, 42) which is referred to as a region of silence and in which the sound of the gradient coils (3) is to be cancelled; b) an adder circuit (51), having inputs which are connected to outputs of the first filter device (39) and an output (63) which is connected to an input of a sound reproducing device which comprises at least one sound reproducer (57) arranged in or near the region of silence (40); andc) a signal delay device (41) for inducing a predetermined time difference between the signal transfer from the gradient signal generator (9) to the gradient coils (3) on the one hand and the signal transfer from the gradient signal generator to the first filter device (39) on the other hand.
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2.发明授权MRI method and device for fast determination of the transverse relaxation time constant T2 失效用于快速确定横向放松时间常数T2的MRI方法和装置
公开(公告)号：US5068610A
公开(公告)日：1991-11-26
申请号：US358327
申请日：1989-05-26
摘要： An MRI method and device for fast determination of the transverse relaxation time constant T2 utilizes the fact that this time constant introduces asymmetry into all magnetic resonance echo signals (::exp(-t/T2) enabling determination of the time constant T2 from the asymmetry of the echo signals. During the determination of a spin density distribution the value of the time constant T2 can be determined for each pixel. After Fourier transformation of the resonance signal, integration of the imaginary terms is performed (in the coordinate direction of the measuring gradient). The quotient of the current integral and the real term of the associated pixel is an accurate measure of the time constant T2 in the relevant pixel.
摘要翻译： 用于快速确定横向弛豫时间常数T2的MRI方法和装置利用这一事实，即该时间常数将不对称性引入所有磁共振回波信号（:: exp（-t / T2），使得能够从不对称性确定时间常数T2 在确定自旋密度分布期间，可以为每个像素确定时间常数T2的值，在谐振信号的傅里叶变换之后，执行虚部的积分（在测量的坐标方向上 梯度），相关像素的当前积分和实数的商是相关像素中时间常数T2的精确测量。
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3.发明授权MRI apparatus having an optimally adjusted detection chain and an enlarged dynamic range 失效具有最佳调节检测链和扩大动态范围的MRI装置
公开(公告)号：US5093621A
公开(公告)日：1992-03-03
申请号：US576324
申请日：1990-08-29
CPC分类号： G01R33/3621 , G01R33/56 , G01R33/583
摘要： An MRI apparatus is proposed with an optimally adjusted gain of the detection chain, said MRI apparatus being used for generating pulse and gradient sequences which comprise an excitation pulse having a predetermined excitation angle and a phase encoding gradient. In order to obtain a data set wherefrom an MR image is reconstructed, the pulse and gradient sequence is repeated a number of times, for example 128 times, while varying the value of the time integral of the phase encoding gradient, for lower profile numbers there being chosen an excitation angle which is smaller or greater than the predetermined excitation angle in order to prevent overdriving of the detection chain. The detection chain of such an apparatus is optimally used for obtaining a data set for an MR image.
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4.发明授权
公开(公告)号：US4879514A
公开(公告)日：1989-11-07
申请号：US196534
申请日：1988-05-19
CPC分类号： G01R33/3607 , G01R33/3621
摘要： The invention relates to a magnetic resonance imaging device comprising a transmitter/receiver which, with the exception of a few components is all digital. The transmitter comprises a digital frequency synthesizer, a single sideband modulator and a selective power amplifier, the single sideband modulator being controlled by a phase locked loop oscillator. The receiver comprises a selective pre-amplifier, a frequency mixing stage which is connected either to an output of the phase locked loop oscillator or to an output of the single sideband modulator, and an analog-to-digital converter which samples the output signal of the frequency mixing stage. The demodulation frequency for the receiver is chosen so that, after demodulation, a frequency band is obtained which is situated to one side of 0 Hz.
摘要翻译： 本发明涉及包括发射器/接收器的磁共振成像装置，所述发射器/接收器除了几个部件之外都是数字的。 发射机包括数字频率合成器，单边带调制器和选择性功率放大器，该单边带调制器由锁相环振荡器控制。 接收机包括选择性前置放大器，连接到锁相环振荡器的输出或与单边带调制器的输出相连接的混频级，以及模数转换器，其对 混频阶段。 选择接收机的解调频率，使得在解调之后，获得位于0Hz一侧的频带。
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公开(公告)号：US5455512A
公开(公告)日：1995-10-03
申请号：US143268
申请日：1993-10-26
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。
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6.发明授权Magnetic resonance imaging method and device for reducing image errors in a magnetic resonance image 失效用于降低磁共振图像中的图像误差的磁共振成像方法和装置
公开(公告)号：US5414359A
公开(公告)日：1995-05-09
申请号：US252133
申请日：1994-05-31
IPC分类号： A61B5/055 , G01R33/32 , G01R33/565 , G01V3/00
CPC分类号： G01R33/56518
摘要： A magnetic resonance imaging method is known for the reduction of image errors in magnetic resonance images which are caused by quantization errors in a DAC (26) for generating a phase encoding gradient waveform in an MRI measuring sequence (ms1, ms2) for generating magnetic resonance signals (S(t), S.sub.1 (t)). The known method has the drawback that inter alia the effect of differential non-linearity of the DAC (26) on the image errors is not taken into account. The invention proposes an MRI method in which such image errors are also reduced. To achieve this, prior to and/or during application of the measuring sequences (ms1, ms2), deviations of phase encoding gradient areas relative to desired areas are determined and image data in an image matrix derived from the resonance signals are corrected on the basis of said deviations.
摘要翻译： 磁共振成像方法已知用于减少由用于产生磁共振的MRI测量序列（ms1，ms2）中的相位编码梯度波形产生的DAC（26）中的量化误差引起的磁共振图像中的图像误差 信号（S（t），S1（t））。 已知的方法具有缺点，特别是不考虑DAC（26）的差分非线性对图像误差的影响。 本发明提出了一种MRI方法，其中这种图像误差也降低。 为了实现这一点，在测量序列（ms1，ms2）应用之前和/或期间，确定相位编码梯度区域相对于期望区域的偏差，并且基于从谐振信号导出的图像矩阵中的图像数据基于 的偏差。
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公开(公告)号：US5023552A
公开(公告)日：1991-06-11
申请号：US607779
申请日：1990-10-24
CPC分类号： G01R33/3621 , G01R33/56
摘要： A magnetic resonance imaging device and method are disclosed in which, during acquisition of measuring data the receiver gain is switched over in dependence of the signal strength, so that in principle every data set of the various measuring cycles has an optimum signal to noise ratio.
摘要翻译： 公开了一种磁共振成像装置和方法，其中在获取测量数据期间，根据信号强度来切换接收机增益，使得原则上各种测量周期的每个数据组具有最佳的信噪比。
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