title: Free-breathing, zero-TE MR lung imaging.
abstract: OBJECTIVE
  The investigation of three-dimensional radial, zero-echo time (TE) imaging for high-resolution, free-breathing magnetic resonance (MR) lung imaging using prospective and retrospective motion correction.
  
  
  METHODS
  Zero-TE was implemented similarly to the rotating-ultra-fast-imaging-sequence, providing 3D, isotropic, radial imaging with proton density contrast. Respiratory motion was addressed using prospective triggering (PT), prospective gating (PG) and retrospective gating (RG) with physiological signals obtained from a respiratory belt and interleaved pencil beam and DC navigators. The methods were demonstrated on four healthy volunteers at 3T.
  
  
  RESULTS
  3D, radial zero-TE imaging with high imaging bandwidth and nominally zero echo-time enables efficient capture of short-lived signals from the lung parenchyma and the vessels. Compared to Cartesian encoding, unaccounted for free-breathing respiration resulted in only benign blurring artifacts confined to the origin of motion. Breath holding froze respiration but achieved only limited image resolution (~1.8 mm, 30 s). PT and PG obtained similar quality expiratory-phase images at 1.2 mm resolution in ~6 min scan time. RG allowed multi-phase imaging in ~15 min, derived from eight individually stored averages.
  
  
  CONCLUSIONS
  Zero-TE appears to be an attractive pulse sequence for 3D isotropic lung imaging. Prospective and retrospective approaches provide high-quality, free-breathing MR lung imaging within reasonable scan time.
authors.affiliation: Department of Information Engineering, EIT, University of Pisa, Largo Lucio Lazzarino 2, 56122, Pisa, Italy, f.gibiino@gmail.com.
authors.forename: Fabio
authors.initials: F
authors.lastname: Gibiino
authors.forename: Laura
authors.initials: L
authors.lastname: Sacolick
authors.forename: Anne
authors.initials: A
authors.lastname: Menini
authors.forename: Luigi
authors.initials: L
authors.lastname: Landini
authors.forename: Florian
authors.initials: F
authors.lastname: Wiesinger
mesh_terms: D000465:Algorithms; D016477:Artifacts; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008168:Lung / Q000033:anatomy & histology*; D010363:Pattern Recognition, Automated / Q000379:methods; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D055425:Respiratory-Gated Imaging Techniques / Q000379:methods*; D012680:Sensitivity and Specificity