title: Apparent diffusion coefficient (ADC) measurement in endometrial carcinoma: effect of region of interest methods on ADC values.
abstract: OBJECTIVE
  To investigate the influence of different-shaped regions of interest (ROIs) on tumor apparent diffusion coefficient (ADC) measurements and interobserver variability in endometrial carcinoma.
  
  
  METHODS
  Sixty-nine patients (age range, 32-92 years; mean, 61 years) were evaluated in this retrospective study. Patients had undergone magnetic resonance (MR) examinations including diffusion-weighted imaging (DWI) using a 3.0-T MR system. Two readers measured tumor ADCs using four ROI methods: freehand ROI; square ROI; round ROI; and five small, round ROIs. Minimum and mean ADCs were obtained. The interclass correlation coefficient (ICC) was statistically analyzed to assess measurement reliability. Repeated-measures analysis of variance was used for comparisons of ADCs measured with each ROI method.
  
  
  RESULTS
  ICCs were 0.93 (minimum ADC) / 0.93 (mean ADC) for freehand ROIs, 0.94/0.95 for square ROIs, 0.94/0.95 for round ROIs, and 0.95/0.96 for five small, round ROIs. All ROI methods indicated excellent correlations. Each minimum ADC was significantly different except between square ROI and round ROI (P < 0.001). Mean ADCs showed significant differences only between freehand ROI and the other ROI methods (P < 0.001).
  
  
  CONCLUSIONS
  ROI shape has no marked influence on ICC in endometrial carcinoma. Compared with minimum ADCs, mean ADCs are suggested to provide more stable results regardless of the ROI method.
authors.affiliation: Division of Radiology, Department of Pathophysiological and Therapeutic Science, Faculty of Medicine, Tottori University, Yonago, Japan.
authors.forename: Chie
authors.initials: C
authors.lastname: Inoue
authors.forename: Shinya
authors.initials: S
authors.lastname: Fujii
authors.forename: Sachi
authors.initials: S
authors.lastname: Kaneda
authors.forename: Takeru
authors.initials: T
authors.lastname: Fukunaga
authors.forename: Toshio
authors.initials: T
authors.lastname: Kaminou
authors.forename: Junzo
authors.initials: J
authors.lastname: Kigawa
authors.forename: Tasuku
authors.initials: T
authors.lastname: Harada
authors.forename: Toshihide
authors.initials: T
authors.lastname: Ogawa
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D016889:Endometrial Neoplasms / Q000473:pathology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: ADC; MR; ROI; apparent diffusion coefficient; diffusion; endometrial carcinoma