title: Interobserver and intraobserver variability of the apparent diffusion coefficient in treated malignant hepatic lesions on a 3.0T machine: measurements in the whole lesion versus in the area with the most restricted diffusion.
abstract: OBJECTIVE
  To assess the inter/intraobserver variability of apparent diffusion coefficient (ADC) measurements in treated hepatic lesions and to compare ADC measurements in the whole lesion and in the area with the most restricted diffusion (MRDA).
  
  
  METHODS
  Twenty-five patients with treated malignant liver lesions were examined on a 3.0T machine. After agreeing on the best ADC image, two readers independently measured the ADC values in the whole lesion and in the MRDA. These measurements were repeated 1 month later. The Bland-Altman method, Spearman correlation coefficients, and the Wilcoxon signed-rank test were used to evaluate the measurements.
  
  
  RESULTS
  Interobserver variability for ADC measurements in the whole lesion and in the MRDA was 0.17 x 10(-3) mm(2)/s [-0.17, +0.17] and 0.43 x 10(-3) mm(2)/s [-0.45, +0.41], respectively. Intraobserver limits of agreement could be as low as [-0.10, +0.12] 10(-3) mm(2)/s and [-0.20, +0.33] 10(-3) mm(2)/s for measurements in the whole lesion and in the MRDA, respectively.
  
  
  CONCLUSIONS
  A limited variability in ADC measurements does exist, and it should be considered when interpreting ADC values of hepatic malignancies. This is especially true for the measurements of the minimal ADC.
authors.affiliation: Department of Radiology, CHUV - University of Lausanne, Lausanne, Switzerland. tluonmac@gmail.com
authors.forename: Tri-Linh C
authors.initials: TL
authors.lastname: Lu
authors.forename: Reto A
authors.initials: RA
authors.lastname: Meuli
authors.forename: Pedro M
authors.initials: PM
authors.lastname: Marques-Vidal
authors.forename: Pierre
authors.initials: P
authors.lastname: Bize
authors.forename: Alban
authors.initials: A
authors.lastname: Denys
authors.forename: Sabine
authors.initials: S
authors.lastname: Schmidt
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016461:Chemoembolization, Therapeutic / Q000379:methods; D015331:Cohort Studies; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008113:Liver Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000473:pathology*; D009367:Neoplasm Staging; D015588:Observer Variation; D011446:Prospective Studies; D018709:Statistics, Nonparametric