title: Recovery of chemical estimates by field inhomogeneity neighborhood error detection (REFINED): fat/water separation at 7 tesla.
abstract: OBJECTIVE
  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.
  
  
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA. spn5@case.edu
authors.forename: Sreenath
authors.initials: S
authors.lastname: Narayan
authors.forename: Satish C
authors.initials: SC
authors.lastname: Kalhan
authors.forename: David L
authors.initials: DL
authors.lastname: Wilson
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology* / Q000502:physiology*; D050154:Adiposity / Q000502:physiology*; D000465:Algorithms; D000818:Animals; D016477:Artifacts; D001834:Body Water / Q000166:cytology*; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods / Q000662:veterinary*; D051379:Mice; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D051598:Whole Body Imaging / Q000379:methods / Q000662:veterinary