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Self‐calibrating GRAPPA operator gridding for radial and spiral trajectories
Author(s) -
Seiberlich Nicole,
Breuer Felix,
Blaimer Martin,
Jakob Peter,
Griswold Mark
Publication year - 2008
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.21565
Subject(s) - spiral (railway) , operator (biology) , computer science , artificial intelligence , computer vision , nuclear magnetic resonance , physics , mathematics , mathematical analysis , chemistry , biochemistry , repressor , transcription factor , gene
Self‐calibrating GRAPPA operator gridding (GROG) is a method by which non‐Cartesian MRI data can be gridded using spatial information from a multichannel coil array without the need for an additional calibration dataset. Using self‐calibrating GROG, the non‐Cartesian datapoints are shifted to nearby k ‐space locations using parallel imaging weight sets determined from the datapoints themselves. GROG employs the GRAPPA Operator, a special formulation of the general reconstruction method GRAPPA, to perform these shifts. Although GROG can be used to grid undersampled datasets, it is important to note that this method uses parallel imaging only for gridding, and not to reconstruct artifact‐free images from undersampled data. The innovation introduced here, namely, self‐calibrating GROG, allows the shift operators to be calculated directly out of the non‐Cartesian data themselves. This eliminates the need for an additional calibration dataset, which reduces the imaging time and also makes the GROG reconstruction more robust by removing possible inconsistencies between the calibration and non‐Cartesian datasets. Simulated and in vivo examples of radial and spiral datasets gridded using self‐calibrating GROG are compared to images gridded using the standard method of convolution gridding. Magn Reson Med 59:930–935, 2008. © 2008 Wiley‐Liss, Inc.