title: Comparison of free-breathing with navigator-controlled acquisition regimes in abdominal diffusion-weighted magnetic resonance images: Effect on ADC and IVIM statistics.
abstract: OBJECTIVE
  To evaluate the effect on diffusion-weighted image-derived parameters in the apparent diffusion coefficient (ADC) and intra-voxel incoherent motion (IVIM) models from choice of either free-breathing or navigator-controlled acquisition.
  
  
  METHODS
  Imaging was performed with consent from healthy volunteers (n = 10) on a 1.5T Siemens Avanto scanner. Parameter-matched free-breathing and navigator-controlled diffusion-weighted images were acquired, without averaging in the console, for a total scan time of ∼10 minutes. Regions of interest were drawn for renal cortex, renal pyramid, whole kidney, liver, spleen, and paraspinal muscle. An ADC diffusion model for these regions was fitted for b-values ≥ 250 s/mm(2) , using a Levenberg-Marquardt algorithm, and an IVIM model was fitted for all images using a Bayesian method.
  
  
  RESULTS
  ADC and IVIM parameters from the two acquisition regimes show no significant differences for the cohort; individual cases show occasional discrepancies, with outliers in parameter estimates arising more commonly from navigator-controlled scans. The navigator-controlled acquisitions showed, on average, a smaller range of movement for the kidneys (6.0 ± 1.4 vs. 10.0 ± 1.7 mm, P = 0.03), but also a smaller number of averages collected (3.9 ± 0.1 vs. 5.5 ± 0.2, P < 0.01) in the allocated time.
  
  
  CONCLUSIONS
  Navigator triggering offers no advantage in fitted diffusion parameters, whereas free-breathing appears to offer greater confidence in fitted diffusion parameters, with fewer outliers, for matched acquisition periods.
authors.affiliation: CR-UK and EPSRC Cancer Imaging Centre, Division of Radiotherapy & Imaging, Institute of Cancer Research, Sutton, Surrey, UK.
authors.forename: Neil P
authors.initials: NP
authors.lastname: Jerome
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Orton
authors.forename: James A
authors.initials: JA
authors.lastname: d'Arcy
authors.forename: David J
authors.initials: DJ
authors.lastname: Collins
authors.forename: Dow-Mu
authors.initials: DM
authors.lastname: Koh
authors.forename: Martin O
authors.initials: MO
authors.lastname: Leach
mesh_terms: D000328:Adult; D000465:Algorithms; D001499:Bayes Theorem; D062485:Breath Holding; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007668:Kidney / Q000473:pathology; D007672:Kidney Cortex / Q000473:pathology; D008099:Liver / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009038:Motion; D064170:Paraspinal Muscles / Q000473:pathology; D012119:Respiration; D013154:Spleen / Q000473:pathology
keywords: abdominal; diffusion; free-breathing; motion; navigator; renal