Reduced spatial side lobes in chemical-shift imaging.
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.
Adalsteinsson
E
E
Radiological Sciences Laboratory, Department of Radiology, Stanford University, Stanford, California 94305-5488, USA. elfar@lucas.stanford.edu
Star-Lack
J
J
Meyer
C H
CH
Spielman
D M
DM
D001921:Brain / Q000378:metabolism; D001923:Brain Chemistry; D006801:Humans; D050356:Lipid Metabolism; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D019047:Phantoms, Imaging; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted