title: Quantitative Susceptibility Mapping: Concepts and Applications.
abstract: OBJECTIVE
  To review the fundamental principles of susceptibility-weighted imaging (SWI) and quantitative susceptibility mapping (QSM), and to discuss recent clinical developments.
  
  
  METHODS
  SWI is a magnetic resonance imaging method that takes advantage of magnitude signal loss and phase information to reveal anatomic and physiologic information about tissue and venous vasculature. The method enhances image contrast qualitatively, relying on phase shifts due to differences in magnetic susceptibility between tissues. QSM, extending SWI in an elegant way, is a new sophisticated postprocessing technique that numerically solves the inverse source-effect problem to derive local tissue magnetic susceptibility (source) from the measured magnetic field distribution (effect) as it is reflected in the phase images of gradient-echo sequences.
  
  
  RESULTS
  SWI has meanwhile been established in numerous clinical as well as basic biomedical applications due to its ability to highlight tissue structures and compounds that are difficult to detect by conventional magnetic resonance imaging (MRI), including iron, calcifications, small veins, blood, and bones. The field of QSM has also progressed rapidly, both in terms of optimizing the post-processing strategies and algorithms as well as in gaining ground for new clinical applications that take advantage of its quantitative nature and improved specificity to identify the magnetic signature of lesions.
  
  
  CONCLUSIONS
  Though magnetic susceptibility may be a major nuisance producing image artifacts in MRI, recent work has transformed it into a useful source of image contrast. Both SWI and QSM are gaining increasing acceptance in clinical practice. In particular, QSM provides new insights into tissue composition and organization due to its more direct relation to the actual physical tissue magnetic properties.
authors.affiliation: Medical Physics Group, Institute for Diagnostic and Interventional Radiology, University Hospital Jena, Friedrich-Schiller University, Philosophenweg 3, 07743, Jena, Germany. juergen.reichenbach@med.uni-jena.de.|Michael Stifel Center for Data-driven and Simulation Science Jena, Friedrich Schiller University, Jena, Germany. juergen.reichenbach@med.uni-jena.de.
authors.forename: J R
authors.initials: JR
authors.lastname: Reichenbach
authors.affiliation: Buffalo Neuroimaging Analysis Center, Department of Neurology, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, USA.|MRI Clinical and Translational Research Center, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, USA.
authors.forename: F
authors.initials: F
authors.lastname: Schweser
authors.affiliation: Medical Physics Group, Institute for Diagnostic and Interventional Radiology, University Hospital Jena, Friedrich-Schiller University, Philosophenweg 3, 07743, Jena, Germany. juergen.reichenbach@med.uni-jena.de.
authors.forename: B
authors.initials: B
authors.lastname: Serres
authors.affiliation: Medical Physics Group, Institute for Diagnostic and Interventional Radiology, University Hospital Jena, Friedrich-Schiller University, Philosophenweg 3, 07743, Jena, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Deistung
mesh_terms: D001921:Brain / Q000473:pathology*; D001927:Brain Diseases / Q000473:pathology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*
keywords: Magnetic resonance imaging; Magnetic susceptibility; Quantitative susceptibility mapping; Susceptibility-weighted imaging