title: Temporally constrained respiratory gating improves continuously moving table MRI during free breathing.
abstract: OBJECTIVE
  To evaluate a novel breathing motion correction algorithm for continuously moving table magnetic resonance imaging (CMT-MRI) that optimizes motion consistency in a fixed time span.
  
  
  METHODS
  In 22 patients CMT-MRI was performed during free breathing. During a preparatory phase (constant) or continuously during the scan (adaptive) gating thresholds were computed from breathing states that should allow for motion consistent k-space sampling. After data from a first k-space traversal was acquired irrespective of breathing motion, subsequently k-space lines with discordant breathing states were reacquired below the gating threshold. Time constraints of CMT-MRI were respected, because a fixed time was allocated for reacquisition. Image quality and lesion depiction were evaluated on images reconstructed from the first traversal and motion-corrected images.
  
  
  RESULTS
  Compared to constant thresholds, gating with adaptive thresholds led to a higher number of reacquired k-space lines (60.1%/41.7%) and a larger fraction of motion consistent final k-space lines (96.6%/78.8%). Adaptive gating induced a significant increase in image quality for all regions affected by breathing motion. Only one of 22 lesions was not depicted on the adaptively corrected images, whereas 15 were readily appreciable.
  
  
  CONCLUSIONS
  Temporally constrained respiratory gating with adaptive thresholds allows for fully sampled, motion-corrected CMT-MRI acquisitions during free breathing.
authors.affiliation: Department of Diagnostic Radiology, University Hospital Freiburg, Germany. tobias.baumann@uniklinik-freiburg.de
authors.forename: Tobias
authors.initials: T
authors.lastname: Baumann
authors.forename: Stefan A R
authors.initials: SA
authors.lastname: Kannengiesser
authors.forename: Matthias
authors.initials: M
authors.lastname: Honal
mesh_terms: D000465:Algorithms; D016477:Artifacts; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009038:Motion; D056888:Patient Positioning / Q000379:methods*; D010386:Pelvic Neoplasms / Q000473:pathology*; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D055425:Respiratory-Gated Imaging Techniques / Q000379:methods*; D012680:Sensitivity and Specificity