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Reduced spatial side lobes in chemical-shift imaging

1999; Wiley; Volume: 42; Issue: 2 Linguagem: Inglês

10.1002/(sici)1522-2594(199908)42

1522-2594

Elfar Adalsteinsson, Josh Star‐Lack, Craig H. Meyer, Daniel M. Spielman,

Medical Imaging Techniques and Applications

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. © 1999 Wiley-Liss, Inc.