title: Subject-specific models of susceptibility-induced B0 field variations in breast MRI.
abstract: OBJECTIVE
  To rapidly calculate and validate subject-specific field maps based on the three-dimensional shape of the bilateral breast volume.
  
  
  METHODS
  Ten healthy female volunteers were scanned at 3 Tesla using a multi-echo sequence that provides water, fat, in-phase, out-of-phase, and field map images. A shape-specific binary mask was automatically generated to calculate a computed field map using a dipole field model. The measured and computed field maps were compared by visualizing the spatial distribution of the difference field map, the mean absolute error, and the 80% distribution widths of frequency histograms.
  
  
  RESULTS
  The 10 computed field maps had a mean absolute error of 38 Hz (0.29 ppm) compared with the measured field maps. The average 80% distribution widths for the histograms of all of the computed, measured, and difference field maps are 205 Hz, 233 Hz, and 120 Hz, respectively.
  
  
  CONCLUSIONS
  The computed field maps had substantial overall agreement with the measured field maps, indicating that breast MRI field maps can be computed based on the air-tissue interfaces. These estimates may provide a predictive model for field variations and thus have the potential to improve applications in breast MRI.
authors.affiliation: Radiology, Stanford University, Stanford, California, USA. cjordan@stanford.edu
authors.forename: Caroline D
authors.initials: CD
authors.lastname: Jordan
authors.forename: Bruce L
authors.initials: BL
authors.lastname: Daniel
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Koch
authors.forename: Huanzhou
authors.initials: H
authors.lastname: Yu
authors.forename: Steve
authors.initials: S
authors.lastname: Conolly
authors.forename: Brian A
authors.initials: BA
authors.lastname: Hargreaves
mesh_terms: D000388:Air; D000465:Algorithms; D001940:Breast / Q000473:pathology*; D001943:Breast Neoplasms / Q000175:diagnosis / Q000473:pathology*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008280:Magnetics; D015233:Models, Statistical; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D015203:Reproducibility of Results