title: Diffusion-weighted magnetic resonance imaging in the characterization of testicular germ cell neoplasms: Effect of ROI methods on apparent diffusion coefficient values and interobserver variability.
abstract: BACKGROUND
  To evaluate the difference in apparent diffusion coefficient (ADC) measurements at diffusion-weighted (DW) magnetic resonance imaging of differently shaped regions-of-interest (ROIs) in testicular germ cell neoplasms (TGCNS), the diagnostic ability of differently shaped ROIs in differentiating seminomas from nonseminomatous germ cell neoplasms (NSGCNs) and the interobserver variability.
  
  
  METHODS
  Thirty-three TGCNs were retrospectively evaluated. Patients underwent MR examinations, including DWI on a 1.5-T MR system. Two observers measured mean tumor ADCs using four distinct ROI methods: round, square, freehand and multiple small, round ROIs. The interclass correlation coefficient was analyzed to assess interobserver variability. Statistical analysis was used to compare mean ADC measurements among observers, methods and histologic types.
  
  
  RESULTS
  All ROI methods showed excellent interobserver agreement, with excellent correlation (P<0.001). Multiple, small ROIs provided the lower mean ADC in TGCNs. Seminomas had lower mean ADC compared to NSGCNs for each ROI method (P<0.001). Round ROI proved the most accurate method in characterizing TGCNS.
  
  
  CONCLUSIONS
  Interobserver variability in ADC measurement is excellent, irrespective of the ROI shape. Multiple, small round ROIs and round ROI proved the more accurate methods for ADC measurement in the characterization of TGCNs and in the differentiation between seminomas and NSGCNs, respectively.
authors.affiliation: Department of Clinical Radiology, Medical School, University of Ioannina, University Campus, 45110, Ioannina, Greece. Electronic address: a_tsili@yahoo.gr.
authors.forename: Athina C
authors.initials: AC
authors.lastname: Tsili
authors.affiliation: Department of Clinical Radiology, Medical School, University of Ioannina, University Campus, 45110, Ioannina, Greece. Electronic address: alexdorkou@hotmail.com.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Ntorkou
authors.affiliation: Department of Medical Physics, Medical School, University of Ioannina, University Campus, 45110, Ioannina, Greece. Electronic address: astrakas@uoi.gr.
authors.forename: Loukas
authors.initials: L
authors.lastname: Astrakas
authors.affiliation: Department of Clinical Radiology, Medical School, University of Ioannina, University Campus, 45110, Ioannina, Greece. Electronic address: vxydis@cc.uoi.gr.
authors.forename: Vasilis
authors.initials: V
authors.lastname: Xydis
authors.affiliation: Department of Urology, Medical School, University of Ioannina, University Campus, 45110, Ioannina, Greece. Electronic address: stamp@gmail.com.
authors.forename: Stavros
authors.initials: S
authors.lastname: Tsampalas
authors.affiliation: Department of Urology, Medical School, University of Ioannina, University Campus, 45110, Ioannina, Greece. Electronic address: akrosnin@hotmail.com.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Sofikitis
authors.affiliation: Department of Clinical Radiology, Medical School, University of Ioannina, University Campus, 45110, Ioannina, Greece. Electronic address: margyrop@cc.uoi.gr.
authors.forename: Maria I
authors.initials: MI
authors.lastname: Argyropoulou
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009373:Neoplasms, Germ Cell and Embryonal / Q000000981:diagnostic imaging* / Q000473:pathology; D015588:Observer Variation; D010808:Physical Examination; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013736:Testicular Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D013737:Testis / Q000000981:diagnostic imaging / Q000473:pathology; D055815:Young Adult
keywords: ADC; Apparent diffusion coefficient; Diffusion; MR imaging; ROI; Testicular germ cell neoplasms