Reduced spatial side lobes in chemical-shift imaging

✍ Scribed by Elfar Adalsteinsson; Josh Star-Lack; Craig H. Meyer; Daniel M. Spielman

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 369 KB
• Volume: 42
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/(sici)1522-2594(199908)42:2<314::aid-mrm14>3.0.co;2-x

✦ Synopsis

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 densityweighted 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.