CORRECTION OF SPATIALLY DEPENDENT PHASE-SHIFTS FOR PARTIAL FOURIER-IMAGING
CORRECTION OF SPATIALLY DEPENDENT PHASE-SHIFTS FOR PARTIAL FOURIER-IMAGING
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DOI：
10.1016/0730-725x(88)90444-4
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发表时间：
1988-03-01
影响因子：
2.5
通讯作者：
VAVREK, RM
中科院分区：
文献类型：
--
作者：
MACFALL, JR;PELC, NJ;VAVREK, RM
部分傅立叶MR图像（PFI）由具有比使用直接傅立叶变换自旋回波采集常规采集的相位编码视图少的相位编码视图的数据构建。PFI数据采集被构造成获得与常规采集相同的空间分辨率，在信噪比降低与采集时间改善之间进行权衡。“缺失”视图可以被零填充，或者如果数据是厄米特的，则由对称性提供（基本算法）。说明了空间相关相移（SDPS）对用填零或基本算法构造的PFI的影响。这种SDPS的原因和典型的幅度进行了讨论。在自旋回波数据，只有低阶，缓慢变化的SDPS，被证明是显着的。通过使用模拟和实际的数据集，这些典型的SDPS被证明产生显着的文物PFI时，丢失的数据量接近一半。当较少的数据丢失时，伪影减少。如果缺失的数据少于25%，则可以使用零填充算法生成良好的图像。开发了在PFI中校正相移的几种方法：具有频率（χ）的基本厄米特算法。方向校正（BAX）、基本傅立叶校正算法（BFC）和改进的迭代傅立叶校正算法（IFC）。当多达46%的数据丢失时，BFC和IFC可以生成良好的图像。具有快速变化的SDPS的数据，例如，梯度重聚焦数据，使得相位校正任务更加困难。然而，在少于25%的数据缺失的情况下，可以创建可接受的梯度重聚焦PFI图像。
Partial Fourier MR images (PFI) are constructed from data that have fewer phase encoding views than are conventionally acquired using direct Fourier transform spin echo acquisition. The PFI data acquisition is structured to obtain the same spatial resolution as conventional acquisition, trading off signal-to-noise reduction for acquisition time improvement. The "missing" views can be zero filled or, if the data are Hermitian, supplied by symmetry (basic algorithm). The effect of spatially dependent phase shifts (SDPS) on PFI constructed with zero-fill or the basic algorithm is illustrated. The causes and typical magnitudes of such SDPS are discussed. In spin echo data only the low order, slowly varying SDPS, is shown to be significant. Through use of simulated and actual data sets these typical SDPS are shown to produce significant artifacts in PFI, when the amount of missing data is close to one-half. The artifacts are reduced when less data are missing. Good images can be generated with the zero-fill algorithm if less than 25% of the data is missing. Several methods of correcting phase shifts in PFI are developed: the basic Hermitian algorithm with frequency (.chi.) direction correction (BAX), basic Fourier correction algorithm (BFC) and an improved iterative Fourier correction algorithm (IFC). The BFC and IFC can produce good images when as much as 46% of the data is missing. Data with rapidly varying SDPS, for example, gradient refocused data, make the phase correction task more difficult. With less than 25% of the data missing, however, acceptable gradient refocused PFI images can be created.