title: Joint estimation of chemical shift and quantitative susceptibility mapping (chemical QSM).
abstract: OBJECTIVE
  The purpose of this work is to address the unsolved problem of quantitative susceptibility mapping (QSM) of tissue with fat where both fat and susceptibility change the MR signal phase.
  
  
  METHODS
  The chemical shift of fat was treated as an additional unknown and was estimated jointly with susceptibility to provide the best data fitting using an automated and iterative algorithm. A simplified susceptibility model was used to calculate an updated value of the chemical shift based on the local magnetic field in each iteration. Numerical simulation, phantom experiments and in vivo imaging were performed. Artifacts were assessed by measuring the susceptibility variance in uniform regions. Accuracy was assessed by comparison with ground truth in simulation, and using a susceptibility matching approach in phantom.
  
  
  RESULTS
  Using the proposed method, artifacts on the QSM image were markedly suppressed in all tested datasets compared with results generated using fixed chemical shifts. Accuracy of the estimated susceptibility was also improved in numerical simulation and phantom experiments.
  
  
  CONCLUSIONS
  A joint estimation of fat content and magnetic susceptibility using an iterative chemical shift update was shown to improve image quality and accuracy on QSM images.
authors.affiliation: Department of Biomedical Engineering, Cornell University, Ithaca, New York, New York, USA.|Department of Radiology, Weill Cornell Medical College, New York, New York, USA.
authors.forename: Alexey V
authors.initials: AV
authors.lastname: Dimov
authors.affiliation: Medimagemetric, LLC, New York, New York, USA.
authors.forename: Tian
authors.initials: T
authors.lastname: Liu
authors.affiliation: Department of Radiology, Weill Cornell Medical College, New York, New York, USA.
authors.forename: Pascal
authors.initials: P
authors.lastname: Spincemaille
authors.affiliation: Department of Radiology, NorthShore University HealthSystem, Evanston, Illinois, USA.|University of Chicago Pritzker School of Medicine, Chicago, Illinois, USA.
authors.forename: Jacob S
authors.initials: JS
authors.lastname: Ecanow
authors.affiliation: Department of Radiology, NorthShore University HealthSystem, Evanston, Illinois, USA.|Department of Surgery (Neurosurgery), University of Chicago, Chicago, Illinois, USA.
authors.forename: Huan
authors.initials: H
authors.lastname: Tan
authors.affiliation: Department of Radiology, NorthShore University HealthSystem, Evanston, Illinois, USA.|Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA.
authors.forename: Robert R
authors.initials: RR
authors.lastname: Edelman
authors.affiliation: Department of Biomedical Engineering, Cornell University, Ithaca, New York, New York, USA.|Department of Radiology, Weill Cornell Medical College, New York, New York, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology*; D000465:Algorithms; D000818:Animals; D016477:Artifacts; D001940:Breast / Q000033:anatomy & histology*; D002417:Cattle; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging
keywords: breast imaging; chemical shift; quantitative susceptibility mapping (QSM); water/fat separation