Adalsteinsson E, Star-Lack J, Meyer C H, Spielman D M
Radiological Sciences Laboratory, Department of Radiology, Stanford University, Stanford, California 94305-5488, USA.
Magn Reson Med. 1999 Aug;42(2):314-23. doi: 10.1002/(sici)1522-2594(199908)42:2<314::aid-mrm14>3.0.co;2-x.
Density-weighted k-space sampling with spiral trajectories is used to reduce spatial side lobes in chemical-shift imaging (CSI). In this method, more time is spent collecting data at the center of k space and less time at the edges of k space in order to make the sampling density proportional to a given apodization function, subject to constraints imposed by gradient performance and Nyquist sampling. The efficient k-space coverage of spiral-based trajectories enables good control over the sampling density within practical in vivo scan times. The density-weighted acquisition is compared to a conventional, nonweighted spiral sampling without the application of a window function. For a fixed voxel size and imaging time, the noise variance is observed to be the same for both cases, while spatial side lobes are greatly reduced with the variable-density sampling. This method is demonstrated on a normal volunteer by imaging of brain metabolites at 1.5 T with both single slice CSI and volumetric CSI. Magn Reson Med 42:314-323, 1999.
采用螺旋轨迹的密度加权k空间采样用于减少化学位移成像（CSI）中的空间旁瓣。在该方法中，在k空间中心收集数据的时间更多，而在k空间边缘收集数据的时间更少，以便使采样密度与给定的变迹函数成比例，同时要受到梯度性能和奈奎斯特采样的限制。基于螺旋轨迹的高效k空间覆盖能够在实际的体内扫描时间内对采样密度进行良好控制。将密度加权采集与未应用窗函数的传统非加权螺旋采样进行比较。对于固定的体素大小和成像时间，观察到两种情况下的噪声方差相同，而变密度采样可大大降低空间旁瓣。通过在1.5T下对正常志愿者进行单切片CSI和容积CSI脑代谢物成像，验证了该方法。《磁共振医学》42:314 - 323，1999年。
