title: Quantitative liver ADC measurements using diffusion-weighted MRI at 3 Tesla: evaluation of reproducibility and perfusion dependence using different techniques for respiratory compensation.
abstract: OBJECTIVE
  Diffusion weighted imaging (DWI) of the liver suffers from low signal to noise making 3 Tesla (3 T) an attractive option, but 3 T data is scarce. It was the aim to study the influence of different b values and respiratory compensation methods (RCM) on the apparent diffusion coefficient (ADC) level and on ADC reproducibility at 3 T.
  
  
  METHODS
  Ten healthy volunteers and 12 patients with malignant liver lesions underwent repeated (2-22 days) breathhold, free-breathing and respiratory triggered DWI at 3 T using b values between 0 and 1,000 s/mm(2).
  
  
  RESULTS
  The ADCs changed up to 150% in healthy livers and up to 48% in malignant lesions depending on b value combinations. Best ADC reproducibility in healthy livers were obtained with respiratory triggering (95% limits of agreement: ±0.12) and free-breathing (±0.14). In malignant lesions equivalent reproducibility was obtained with less RCM dependence. The use of a lower maximum b value (b = 500) decreased reproducibility (±0.14 to ±0.32) in both normal liver and malignant lesions.
  
  
  CONCLUSIONS
  Large differences in absolute ADC values and reproducibility caused by varying combinations of clinically realistic b values were demonstrated. Different RCMs caused smaller differences. Lowering maximum b value to 500 increased limits of agreement up to a factor of two. Serial ADC changes larger than approximately 15% can be detected confidently on an individual basis in both malignant lesions and normal liver parenchyma at 3 T using appropriate b values and respiratory compensation.
authors.affiliation: Department of Radiology, NBG, Aarhus University Hospital, Nørrebrogade 44, 8000, Århus C, Denmark, niselbroend@hotmail.com.
authors.forename: Nis Elbrønd
authors.initials: NE
authors.lastname: Larsen
authors.forename: Søren
authors.initials: S
authors.lastname: Haack
authors.forename: Lars Peter Skovgaard
authors.initials: LP
authors.lastname: Larsen
authors.forename: Erik Morre
authors.initials: EM
authors.lastname: Pedersen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D016477:Artifacts; D004058:Diffusion; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008099:Liver / Q000473:pathology*; D008113:Liver Neoplasms / Q000175:diagnosis* / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009068:Movement; D010477:Perfusion; D015203:Reproducibility of Results; D012119:Respiration; D059629:Signal-To-Noise Ratio; D055815:Young Adult