title: Apparent diffusion coefficient (ADC) measurement in ovarian tumor: Effect of region-of-interest methods on ADC values and diagnostic ability.
abstract: OBJECTIVE
  To investigate the difference in apparent diffusion coefficient (ADC) measurements of differently shaped regions of interest (ROIs) in ovarian tumors, and to investigate the diagnostic ability of differently shaped ROIs in differentiating benign from malignant ovarian tumors.
  
  
  METHODS
  Fifty-four patients with ovarian tumors with a solid component were evaluated. The patients underwent magnetic resonance (MR) examinations including diffusion-weighted imaging using a 3.0T MR system. Two readers measured ADCs using four ROI methods: freehand, square, round, and five small round ROIs. The interclass correlation coefficient (ICC) and repeated-measures analysis of variance were used to assess their measurement reliability and to compare ADCs for each ROI method. Receiver operating characteristic curve analysis and unpaired t-test on each ROI were used to differentiate benign and malignant ovarian tumors and assess the diagnostic ability.
  
  
  RESULTS
  All ROI methods except the square ROI (0.56) showed good or excellent correlations (0.70-0.91). Minimum and mean ADC values differed significantly between the ROIs (P < 0.05). When using the freehand ROI, the minimum and mean ADC values were the lowest and highest, respectively. The optimal cutoff minimum and mean ADC values of each ROI for differentiating benign and malignant tumors were 0.81-1.06 × 10(-3) mm(2) /s and 1.15-1.52 × 10(-3) mm(2) /s, respectively. The areas under the curve showed no significant differences among the ADCs in the different ROI methods (P > 0.05). Minimum and mean ADCs from all ROIs showed significant differences between benign and malignant tumors (P < 0.05).
  
  
  CONCLUSIONS
  The ROI shape influences ADC values and the optimal cutoff ADC values for differentiating benign from malignant ovarian tumors.
authors.affiliation: Division of Radiology, Department of Pathophysiological and Therapeutic Science, Faculty of Medicine, Tottori University, Yonago, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Mukuda
authors.affiliation: Division of Radiology, Department of Pathophysiological and Therapeutic Science, Faculty of Medicine, Tottori University, Yonago, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Fujii
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.affiliation: Division of Radiology, Department of Pathophysiological and Therapeutic Science, Faculty of Medicine, Tottori University, Yonago, Japan.
authors.forename: Takeru
authors.initials: T
authors.lastname: Fukunaga
authors.affiliation: Division of Radiology, Department of Pathophysiological and Therapeutic Science, Faculty of Medicine, Tottori University, Yonago, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Tanabe
authors.affiliation: Division of Reproductive-Perinatal Medicine and Gynecological Oncology, Department of Surgery, Faculty of Medicine, Tottori University, Yonago, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Itamochi
authors.affiliation: Division of Radiology, Department of Pathophysiological and Therapeutic Science, Faculty of Medicine, Tottori University, Yonago, Japan.
authors.forename: Toshihide
authors.initials: T
authors.lastname: Ogawa
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D008875:Middle Aged; D009336:Necrosis; D015588:Observer Variation; D010051:Ovarian Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D012372:ROC Curve; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D055815:Young Adult
keywords: MR; ROI; apparent diffusion coefficient; benign; malignant; ovarian tumor