Faster MR Imaging Methods
Faster MR Imaging Methods
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更快的 MR 成像方法
DOI：
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发表时间：
1986
期刊：
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通讯作者：
F. Schmitt
中科院分区：
文献类型：
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作者：
P. Margosian;F. Schmitt
这里探索了两种不同类型的方法来更快地获取磁共振数据。第一套方法使用正常测量次数的一半，并能够将采集时间缩短到原来的1/2。第二种方法使用来自多个回波的测量结果来合成“传统的”自旋-翘曲原始数据集。第二种方法能够将数据采集时间缩短四到八倍。测试了三种“数据的一半”方法。第一种方法使用相位编码步骤的中间半部分，并使用正弦内插在通常的256×256矩阵上重建；使用第一种方法，提高了信噪比，但降低了相位编码方向的空间分辨率。第二种方法使用正常相位编码步骤的所有上(或下)半部分，将它们放置在否则为空的256×256矩阵中，重建、进行相位校正、取实数部分。这种‘半傅立叶’方法使用相位信息来保持全分辨率，只用一半的数据(实际上是53%)，但以降低信噪比为代价。对于第三种方法，每隔2个阶段进行一次编码测量，在数据空间的中心加上8个额外部分，用三次内插填充空的数据行，并进行FFT重构。这种方法保持了空间分辨率和信噪比，但由于该方法固有的欠采样，出现了两幅“鬼影”图像(低幅度)。用于更快数据采集的“多回波”方法利用从不同回波获取数据中的不同相位编码步骤的序列。最好的策略是从编号最低的回波中进行中心(低频)测量，从后面的回波中进行较高频率的测量。该方法的实用细节包括对不同回波测量的位置、相位和幅度进行校正。同样重要的是使用数据采集序列，这些序列针对受刺激的回波和涡流进行了很好的调整。其结果是，对于自旋翘曲成像，数据采集速度可以比正常快四到八倍，几乎保持了全分辨率，信噪比略有降低。
Two different types of methods for acquiring MR data more quickly have been explored here. The first set of methods uses half the normal number of measurements and is capable of shortening acquisition times by a factor of two. The second type of method uses measurements from multiple echoes to synthesize a 'conventional' spin-warp raw data set. This second method is capable of shortening data acquisition times by factors of four to eight. Three types of 'half the data' methods have been tested. The first uses the central half of the phase encoding steps, and reconstructs on the usual 256 x 256 matrix using a sinc interpolation; with this first method, signal to noise ratio is improved, but spatial resolution in the phase encoding direction is reduced. The second method uses all the upper (or lower) half of the normal phase encoding steps, places them in an otherwise empty 256 x 256 matrix, reconstructs, makes a phase correction, takes the real part. This 'half Fourier' method uses the phase information to retain full resolution with only half the data (really 53%) but at the cost of a reduction of signal to noise ratio. for the third method, every second phase encoding measurement is taken, along with eight extras in the center of the data space, empty data lines are filled by cubic interpolation, and a FFT recontruction is done. For this method, spatial resolution and signal to noise ratio are maintained, but two 'ghost' images (low amplitude-occur because of the inherent undersampling of this method. The 'multiple echo' method for faster data acquisition makes use of a sequence that acquires different phase encoding steps in the data from different echoes. the best strategy is to take the central (low frequency) measurements from the lowest numbered echoes, and the higher frequency measurements from the later echoes. The practical details of this method include correcting position, phase, and amplitude of measurements from different echoes. It is also important to use data acquisition sequences that are very well adjusted refered to stimulated echoes and eddy currents. The result is that data can be acquired four to eight times faster than normal for spin-warp imaging, almost full resolution is retained, and signal to noise ratio is reduced somewhat.