title: Inter- and intraobserver variability in the evaluation of dynamic breast cancer MRI.
abstract: OBJECTIVE
  To quantify variations within and between observers ascribable to manual region of interest (ROI) placement in patients with breast cancer undergoing dynamic MRI.
  
  
  METHODS
  Expert and nonexpert observers independently outlined tumor ROIs on 30 dynamic T(1)-weighted (T(1)W) MRI scans on five occasions over two months. Lesion size (number of pixels) and kinetic parameter estimates, including the transfer constant (K(trans)), were calculated for each ROI placement. Inter- and intraobserver variability was assessed with respect to the interval between drawings, lesion morphology, and observer experience.
  
  
  RESULTS
  For the nonexpert, the variability reduced with decreasing time intervals between ROI drawings (the coefficient of variance (wCV) values at two months, two weeks, one day, and same-day time intervals were respectively 11.6%, 10.7%, 4.8%, and 2.6% for lesion size, and 8.9%, 9.7%, 6.7%, and 3.2% for K(trans)). For the expert observer, the variability was smaller overall and more constant, but improved for same-day ROI placements (region size wCV: 7.5%, 6.2%, 7.1%, and 3.7%; K(trans) wCV: 5.4%, 5.3%, 5.6%, and 4.5%).
  
  
  CONCLUSIONS
  Significant observer variability in manual ROI placement occurs in dynamic MRI of breast cancer. For serial patient studies, ROI placements should be outlined at the same sitting to minimize observer error.
authors.affiliation: Mount Vernon Cancer Centre, Northwood, United Kingdom. mjberesford@yahoo.co.uk
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Beresford
authors.forename: Anwar R
authors.initials: AR
authors.lastname: Padhani
authors.forename: N Jane
authors.initials: NJ
authors.lastname: Taylor
authors.forename: Mei-Lin
authors.initials: ML
authors.lastname: Ah-See
authors.forename: J James
authors.initials: JJ
authors.lastname: Stirling
authors.forename: Andreas
authors.initials: A
authors.lastname: Makris
authors.forename: James A
authors.initials: JA
authors.lastname: d'Arcy
authors.forename: David J
authors.initials: DJ
authors.lastname: Collins
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000473:pathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data*; D008875:Middle Aged; D015588:Observer Variation; D011361:Professional Competence / Q000706:statistics & numerical data*; D011785:Quality Assurance, Health Care / Q000379:methods; D012372:ROC Curve; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013647:Task Performance and Analysis