title: Navigator artifact reduction in three-dimensional late gadolinium enhancement imaging of the atria.
abstract: OBJECTIVE
  Navigator-gated three-dimensional (3D) late gadolinium enhancement (LGE) imaging demonstrates scarring following ablation of atrial fibrillation. An artifact originating from the slice-selective navigator-restore pulse is frequently present in the right pulmonary veins (PVs), obscuring the walls and making quantification of enhancement difficult. We describe a simple sequence modification to greatly reduce or remove this artifact.
  
  
  METHODS
  A navigator-gated inversion-prepared gradient echo sequence was modified so that the slice-selective navigator-restore pulse was delayed in time from the nonselective preparation (NAV-restore-delayed). Both NAV-restore-delayed and conventional 3D LGE acquisitions were performed in 11 patients and the results compared.
  
  
  RESULTS
  One patient was excluded due to severe respiratory motion artifact in both NAV-restore-delayed and conventional acquisitions. Moderate to severe artifact was present in 9 of the remaining 10 patients using the conventional sequence and was considerably reduced when using the NAV-restore-delayed sequence (ostial PV to blood pool ratio, 1.7 ± 0.5 versus 1.1 ± 0.2, respectively [P < 0.0001]; qualitative artifact scores, 2.8 ± 1.1 versus 1.2 ± 0.4, respectively [P < 0.001]). While navigator signal-to-noise ratio was reduced with the NAV-restore-delayed sequence, respiratory motion compensation was unaffected.
  
  
  CONCLUSIONS
  Shifting the navigator-restore pulse significantly reduces or eliminates navigator artifact. This simple modification improves the quality of 3D LGE imaging and potentially aids late enhancement quantification in the atria.
authors.affiliation: Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Trust, London, UK.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Keegan
authors.forename: Peter
authors.initials: P
authors.lastname: Drivas
authors.forename: David N
authors.initials: DN
authors.lastname: Firmin
mesh_terms: D016477:Artifacts; D003287:Contrast Media; D017352:Echo-Planar Imaging / Q000379:methods*; D006325:Heart Atria / Q000033:anatomy & histology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D009942:Organometallic Compounds; D011667:Pulmonary Veins / Q000033:anatomy & histology*; D059629:Signal-To-Noise Ratio
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; C090600:gadobutrol
keywords: artifact; late gadolinium enhancement imaging; navigator; pulmonary veins