title: Intraobserver and interobserver variability in the calculation of apparent diffusion coefficient (ADC) from diffusion-weighted magnetic resonance imaging (DW-MRI) of breast tumours.
abstract: OBJECTIVE
  This study evaluated intraobserver and interobserver variability in the measurement of apparent diffusion coefficient (ADC) values in breast carcinomas.
  
  
  METHODS
  Twenty-eight patients with solid breast lesions >10 mm underwent conventional contrast-enhanced magnetic resonance imaging (MRI) and diffusion-weighted MRI (DW-MRI). Two observers (expert and trainee) segmented the lesion from the surrounding breast tissue on DW images with high b-value (1,000 s/mm(2)). This analysis was repeated by the expert reader after 6 months. Volumes were analysed to obtain mean, median and standard deviation (SD) of the ADC values. Interobserver and intraobserver variation was analysed using the Bland-Altman graph.
  
  
  RESULTS
  All lesions were breast carcinomas, with a mean ADC value of 1.07 × 10(-3) mm(2)/s. The mean of the differences was 0.012 × 10(-3) mm(2)/s, corresponding to an intraobserver variability of 1.1% (limits of agreement: -5%/+8%). The mean interobserver difference was 0.022 × 10(-3) mm(2)/s, corresponding to an interobserver variability of 2% (limits of agreement: -9%/+14%).
  
  
  CONCLUSIONS
  We found a low intraobserver and interobserver variability in calculating ADC in breast carcinomas, which supports its potential use in routine clinical practice.
authors.affiliation: Divisione di Radiologia, Istituto Europeo di Oncologia, Via Ripamonti 435, 20141, Milano, Italy. giuseppe.petralia@ieo.it
authors.forename: G
authors.initials: G
authors.lastname: Petralia
authors.forename: L
authors.initials: L
authors.lastname: Bonello
authors.forename: P
authors.initials: P
authors.lastname: Summers
authors.forename: L
authors.initials: L
authors.lastname: Preda
authors.forename: A
authors.initials: A
authors.lastname: Malasevschi
authors.forename: S
authors.initials: S
authors.lastname: Raimondi
authors.forename: R
authors.initials: R
authors.lastname: Di Filippi
authors.forename: M
authors.initials: M
authors.lastname: Locatelli
authors.forename: G
authors.initials: G
authors.lastname: Curigliano
authors.forename: G
authors.initials: G
authors.lastname: Renne
authors.forename: M
authors.initials: M
authors.lastname: Bellomi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000473:pathology*; D003287:Contrast Media; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis; D008875:Middle Aged; D015588:Observer Variation
chemical_list: D003287:Contrast Media