title: Quantification and correction of respiration induced dynamic field map changes in fMRI using 3D single shot techniques.
abstract: OBJECTIVE
  Respiration induced dynamic field map changes in the brain are quantified and the influence on the magnitude signal (physiological noise) is investigated. Dynamic off-resonance correction allows to reduce the signal fluctuations overlaying the blood oxygenation level dependent signal in T2*-weighted functional imaging.
  
  
  METHODS
  A single-shot whole brain imaging technique with 100 ms temporal resolution was used to measure dynamic off-resonance maps that were calculated from the incremental changes of the image phase. These off-resonance maps are then used to dynamically update the off-resonance corrected reconstruction.
  
  
  RESULTS
  A global resonance offset and a pronounced gradient in head-foot direction were identified as the main components of the change during a respiration cycle. On average, correction for these fluctuations decreases the magnitude fluctuations by around 30%.
  
  
  CONCLUSIONS
  Single shot 3D imaging allows for a robust quantification of dynamic off-resonance changes in the brain. Correction for these fluctuations removes the physiological noise component associated with dynamic point spread function changes.
authors.affiliation: Department of Medicine, University of Hawaii, John A. Burns School of Medicine, Honolulu, Hawaii, USA.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Zahneisen
authors.forename: Jakob
authors.initials: J
authors.lastname: Assländer
authors.forename: Pierre
authors.initials: P
authors.lastname: LeVan
authors.forename: Thimo
authors.initials: T
authors.lastname: Hugger
authors.forename: Marco
authors.initials: M
authors.lastname: Reisert
authors.forename: Thomas
authors.initials: T
authors.lastname: Ernst
authors.forename: Jürgen
authors.initials: J
authors.lastname: Hennig
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D055425:Respiratory-Gated Imaging Techniques / Q000379:methods*; D012680:Sensitivity and Specificity