title: Focal liver lesions detection: Comparison of respiratory-triggering, triggering and tracking navigator and tracking-only navigator in diffusion-weighted imaging.
abstract: OBJECTIVE
  To compare low b value (10s/mm(2)) spin-echo echo-planar (SE-EP) diffusion-weighted imaging (DWI) acquired with respiratory-triggering (RT), triggering and tracking navigator (TT), tracking only navigator (TRON) techniques for image quality and focal liver lesions (FLL) detection in non-cirrhotic patients.
  
  
  METHODS
  This bi-centric study was approved by the institutional review boards; informed consent was obtained. Eighty-three patients were prospectively included and SE-EP-DWI with RT, TT and TRON techniques were performed. DWI sequences were randomized and independently analyzed by two readers. The qualitative evaluation was based on a 3-point score for axial artifacts (motion, ghost, susceptibility artifacts and distortion) and stair-step artifacts. Sensitivity of FLL detection was calculated for all lesions together and after lesion size stratification (≤ 10 mm, >10-20mm and >20mm). The standard of reference consisted of a retrospective reading of the conventional MRI, the three DWI sequences and by follow-up (12 months): a total of 409 FLL were detected. Data between sequences was compared with non-parametric tests. Cohen's kappa coefficient was used for inter-observer agreement.
  
  
  RESULTS
  Image quality was comparable for RT and TT. TRON showed statistically significantly more axial artifacts for the two readers (p<0.05). Stair-step artifacts were not statistically significantly different between DWI sequences. Overall sensitivities for RT, TT, TRON were 85%, 86%, 82% and 86%, 89% 83%, respectively, for readers 1 and 2. The inter-observer agreement was very good.
  
  
  CONCLUSIONS
  Image quality was better for RT and TT compared to TRON. Overall sensitivities for FLL detection were comparable between techniques and readers.
authors.affiliation: Department of Radiology, Clinics of MRI, Hôpital Erasme Université Libre de Bruxelles, 808 Route de Lennik B, 1070 Bruxelles, Belgium.
authors.forename: Said El
authors.initials: SE
authors.lastname: Bouchaibi
authors.affiliation: Department of Radiology AZ Sint-Jan Brugge - Oostende AV, Campus Brugge, Ruddershove 10, B-8000 Brugge, Belgium.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Coenegrachts
authors.affiliation: Department of Radiology, Clinics of MRI, Hôpital Erasme Université Libre de Bruxelles, 808 Route de Lennik B, 1070 Bruxelles, Belgium.
authors.forename: Maria Antonietta
authors.initials: MA
authors.lastname: Bali
authors.affiliation: Department of Radiology, Clinics of MRI, Hôpital Erasme Université Libre de Bruxelles, 808 Route de Lennik B, 1070 Bruxelles, Belgium.
authors.forename: Julie
authors.initials: J
authors.lastname: Absil
authors.affiliation: Department of Radiology, Clinics of MRI, Hôpital Erasme Université Libre de Bruxelles, 808 Route de Lennik B, 1070 Bruxelles, Belgium. Electronic address: tmetens@ulb.ac.be.
authors.forename: Thierry
authors.initials: T
authors.lastname: Metens
authors.affiliation: Department of Radiology, Clinics of MRI, Hôpital Erasme Université Libre de Bruxelles, 808 Route de Lennik B, 1070 Bruxelles, Belgium.
authors.forename: Celso
authors.initials: C
authors.lastname: Matos
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D006528:Carcinoma, Hepatocellular / Q000175:diagnosis; D003287:Contrast Media / Q000008:administration & dosage; D003560:Cysts / Q000175:diagnosis; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods* / Q000592:standards; D017352:Echo-Planar Imaging / Q000379:methods* / Q000706:statistics & numerical data; D005260:Female; D020518:Focal Nodular Hyperplasia / Q000175:diagnosis; D005500:Follow-Up Studies; D006391:Hemangioma / Q000175:diagnosis; D006801:Humans; D007089:Image Enhancement / Q000379:methods* / Q000592:standards; D008113:Liver Neoplasms / Q000175:diagnosis* / Q000556:secondary; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012015:Reference Standards; D055425:Respiratory-Gated Imaging Techniques / Q000379:methods* / Q000592:standards; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media
keywords: Diffusion-weighted MRI; Focal liver lesions; Liver; Navigators; Respiratory synchronization