Recovery of chemical estimates by field inhomogeneity neighborhood error detection (REFINED): Fat/Water separation at 7 tesla
Article first published online: 28 SEP 2012
Copyright © 2012 Wiley Periodicals, Inc.
Journal of Magnetic Resonance Imaging
Volume 37, Issue 5, pages 1247–1253, May 2013
How to Cite
Narayan, S., Kalhan, S. C. and Wilson, D. L. (2013), Recovery of chemical estimates by field inhomogeneity neighborhood error detection (REFINED): Fat/Water separation at 7 tesla. J. Magn. Reson. Imaging, 37: 1247–1253. doi: 10.1002/jmri.23826
- Issue published online: 17 APR 2013
- Article first published online: 28 SEP 2012
- Manuscript Accepted: 15 AUG 2012
- Manuscript Received: 14 FEB 2011
- B0 field map estimation;
- fat–water imaging;
- Dixon imaging;
- fat–water swap;
- Markov random field;
- iterated conditional modes
To reduce swaps in fat–water separation methods, a particular issue on 7 Tesla (T) small animal scanners due to field inhomogeneity, using image postprocessing innovations that detect and correct errors in the B0 field map.
Materials and Methods:
Fat–water decompositions and B0 field maps were computed for images of mice acquired on a 7T Bruker BioSpec scanner, using a computationally efficient method for solving the Markov Random Field formulation of the multi-point Dixon model. The B0 field maps were processed with a novel hole-filling method, based on edge strength between regions, and a novel k-means method, based on field-map intensities, which were iteratively applied to automatically detect and reinitialize error regions in the B0 field maps. Errors were manually assessed in the B0 field maps and chemical parameter maps both before and after error correction.
Partial swaps were found in 6% of images when processed with FLAWLESS. After REFINED correction, only 0.7% of images contained partial swaps, resulting in an 88% decrease in error rate. Complete swaps were not problematic.
Ex post facto error correction is a viable supplement to a priori techniques for producing globally smooth B0 field maps, without partial swaps. With our processing pipeline, it is possible to process image volumes rapidly, robustly, and almost automatically. J. Magn. Reson. Imaging 2013;37:1247–1253. © 2012 Wiley Periodicals, Inc.