title: Simultaneous acquisition of image and navigator slices using CAIPIRINHA for 4D MRI.
abstract: OBJECTIVE
  Respiratory organ motion is still the major challenge of various image-guided treatments in the abdomen. Dynamic organ motion tracking, necessary for the treatment control, can be performed with volumetric time-resolved MRI that sequentially acquires one image and one navigator slice. Here, a novel imaging method is proposed for truly simultaneous high temporal resolution acquisition.
  
  
  METHODS
  A standard balanced steady state free precession sequence was modified to simultaneously acquire two superimposed slices with different phase cycles, namely an image and a navigator slice. Instead of multiband RF pulses, two separate RF pulses were used for the excitation. Images were reconstructed using offline CAIPIRINHA reconstruction. Phantom and in vivo measurements of healthy volunteers were performed and evaluated.
  
  
  RESULTS
  Phantom and in vivo measurements showed good image quality with high signal-to-noise ratio (SNR) and no reconstruction issues.
  
  
  CONCLUSIONS
  We present a novel imaging method for truly simultaneous acquisition of image and navigator slices for four-dimensional (4D) MRI of organ motion. In this method, the time lag between the sequential acquisitions is eliminated, leading to an improved accuracy of organ motion models, while CAIPIRINHA reconstruction results in an improved SNR compared with an existing 4D MRI approach.
authors.affiliation: Department of Radiology, Division of Radiological Physics, University of Basel Hospital, Basel, Switzerland; MRC Department, MPI for Biological Cybernetics, Tübingen, Germany.
authors.forename: Zarko
authors.initials: Z
authors.lastname: Celicanin
authors.forename: Oliver
authors.initials: O
authors.lastname: Bieri
authors.forename: Frank
authors.initials: F
authors.lastname: Preiswerk
authors.forename: Philippe
authors.initials: P
authors.lastname: Cattin
authors.forename: Klaus
authors.initials: K
authors.lastname: Scheffler
authors.forename: Francesco
authors.initials: F
authors.lastname: Santini
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001931:Brain Mapping / Q000379:methods*; D005071:Evoked Potentials / Q000502:physiology; D005240:Feasibility Studies; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: 4D-MRI; CAIPIRINHA; motion tracking; navigator; organ motion; steady state