title: Whole-lesion apparent diffusion coefficient (ADC) metrics as a marker of breast tumour characterization-comparison between ADC value and ADC entropy.
abstract: OBJECTIVE
  To prospectively assess the role of whole-lesion apparent diffusion coefficient (ADC) metrics in the characterization of breast tumours by comparing ADC value with ADC entropy.
  
  
  METHODS
  49 patients with 53 breast lesions underwent phased-array breast coil 1.5-T MRI. Two radiologists experienced in breast MRI, blinded to the final diagnosis, reviewed the ADC maps and placed a volume of interest on all slices including each lesion on the ADC map to obtain whole-lesion mean ADC value and ADC entropy. The mean ADC value and ADC entropy in benign and malignant lesions were compared by the Mann-Whitney U-test. Receiver-operating characteristic analysis was performed to assess the sensitivity and specificity of the two variables in the characterization of the breast lesions.
  
  
  RESULTS
  The benign (n = 19) and malignant lesions (n = 34) had mean diameters of 20.8 mm (10.1-31.5 mm) and 26.4 mm (10.5-42.3 mm), respectively. The mean ADC value of the malignant lesions was significantly lower than that of the benign ones (0.87 × 10-3vs 1.49 × 10-3mm2s-1; p < 0.0001). Malignant ADC entropy was higher than benign entropy, without reaching levels of statistical significance (5.4 vs 5.0; p = 0.064). At a mean ADC cut-off value of 1.16 × 10-3mm2s-1, the sensitivity and specificity for diagnosing malignancy became optimal (97.1% and 93.7, respectively) with an area under the curve (AUC) of 0.975. With regard to ADC entropy, the sensitivity and specificity at a cut-off of 5.18 were 67.6 and 68.7%, respectively, with an AUC of 0.664.
  
  
  CONCLUSIONS
  Whole-lesion mean ADC could be a helpful index in the characterization of suspicious breast lesions, with higher sensitivity and specificity than ADC entropy. Advances in knowledge: Two separate parameters of the whole-lesion histogram were compared for their diagnostic accuracy in characterizing breast lesions. Mean ADC was found to be able to characterize breast lesions, whereas entropy proved to be unable to differentiate benign from malignant breast lesions. It is, however, likely that entropy may distinguish these two groups if a larger cohort were used, or the fact that this may be influenced by the molecular subtypes of breast cancers included.
authors.affiliation: 1 Department of Medical Imaging University Hospital of loannina, loannina, Greece.
authors.forename: Haralambos
authors.initials: H
authors.lastname: Bougias
authors.affiliation: 2 Department of Medical Imaging IASO Maternity Hospital, Athens, Greece.
authors.forename: Abraham
authors.initials: A
authors.lastname: Ghiatas
authors.affiliation: 2 Department of Medical Imaging IASO Maternity Hospital, Athens, Greece.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Priovolos
authors.affiliation: 3 Department of Medical Imaging Chatzikosta General Hospital of loannina, loannina, Greece.
authors.forename: Konstantia
authors.initials: K
authors.lastname: Veliou
authors.affiliation: 4 Department of Medical Imaging, Doncaster and Bassetlaw Hospitals NHS Foundation Trust, Doncaster, UK.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Christou
mesh_terms: D000328:Adult; D000368:Aged; D001940:Breast / Q000000981:diagnostic imaging / Q000473:pathology; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity