title: Utility of real-time field control in T2 *-Weighted head MRI at 7T.
abstract: Real-time field control can serve to reduce respiratory field perturbations during T2 * imaging at high fields. This work investigates the effectiveness of this approach in relation to key variables such as patient physique, breathing patterns, slice location, and the choice of sequence.
  
  
  
  To cover variation in physical constitution and breathing behavior, volunteers with a wide range of body-mass-indices were asked to breathe either normally or deeply during T2 *-weighted image acquisition at 7T. Ensuing field fluctuation was countered by real-time field control or merely recorded in reference experiments. The impact of the control system on image quality was assessed by classifying and grading artifacts related to field fluctuation.
  
  
  
  The amplitude of respiratory field changes and related artifacts were generally stronger for subjects with higher body-mass-index and for lower slices. Field control was found effective at mitigating all five types of artifacts that were studied. Overall image quality was systematically improved. Residual artifacts in low slices are attributed to insufficient spatial order of the control system.
  
  
  
  Real-time field control was found to be a robust means of countering respiratory field perturbations in variable conditions encountered in high-field brain imaging. Reducing net fluctuation, it generally expands the feasibility of high-field T2 * imaging toward challenging patients and brain regions. Magn Reson Med 76:430-439, 2016. © 2015 Wiley Periodicals, Inc.
authors: Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland.
authors: Yolanda
authors: Y
authors: Duerst
authors: Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland.|Skope Magnetic Resonance Technologies, Zurich, Switzerland.
authors: Bertram J
authors: BJ
authors: Wilm
authors: Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland.
authors: Michael
authors: M
authors: Wyss
authors: Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland.
authors: Benjamin E
authors: BE
authors: Dietrich
authors: Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland.
authors: Simon
authors: S
authors: Gross
authors: Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland.
authors: Thomas
authors: T
authors: Schmid
authors: Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland.
authors: David O
authors: DO
authors: Brunner
authors: Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland.
authors: Klaas P
authors: KP
authors: Pruessmann
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology*; D003199:Computer Systems; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D004574:Electromagnetic Fields; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D011874:Radiometry / Q000379:methods; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D055425:Respiratory-Gated Imaging Techniques / Q000379:methods*; D012680:Sensitivity and Specificity
keywords: 7 Tesla; NMR field probes; T2*-weighted imaging; dynamic shimming; field camera; field control