title: Monitoring and compensating phase imperfections in cine balanced steady-state free precession.
abstract: OBJECTIVE
  To analyze and correct for eddy current-induced phase imperfections in cardiac cine balanced steady-state free precession (bSSFP) imaging.
  
  
  METHODS
  Eddy current-induced phase offsets were measured for different phase-encoding schemes using a higher order dynamic field camera. Based on these measurements, offset phases were corrected for in postprocessing and by run-time phase compensation applying radiofrequency phase increments and additional compensatory gradient areas. The findings were validated using numerical simulations, phantom experiments, and in vivo cardiac scans.
  
  
  RESULTS
  Depending on the phase-encoding scheme, significant eddy current-induced phase offsets were detected. Time-varying phase offsets were observed at subsequent excitations leading to steady-state distortions and hence to profile-dependent amplitude modulations in k-space. Taking into account measured k-space trajectories algebraic image reconstruction allowed compensating imperfect spatial encoding. Correction of amplitude modulations was successfully accomplished by run-time phase compensation.
  
  
  CONCLUSIONS
  Using magnetic field monitoring, artifacts in cine balanced steady-state free precession caused by uncompensated eddy current fields can be significantly reduced.
authors: Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.
authors: Rudolf Fritz
authors: RF
authors: Fischer
authors: Christoph
authors: C
authors: Barmet
authors: Markus
authors: M
authors: Rudin
authors: Peter
authors: P
authors: Boesiger
authors: Klaas Paul
authors: KP
authors: Pruessmann
authors: Sebastian
authors: S
authors: Kozerke
mesh_terms: D000465:Algorithms; D016477:Artifacts; D006321:Heart / Q000033:anatomy & histology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D019028:Magnetic Resonance Imaging, Cine / Q000295:instrumentation / Q000379:methods*; D010363:Pattern Recognition, Automated / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: balanced SSFP; cine imaging; eddy currents; magnetic field monitoring; steady-state free precession