title: Diffusion-weighted MR imaging of thyroid nodules.
abstract: BACKGROUND
  The purpose of our study was to determine the diagnostic role of diffusion-weighted imaging (DWI) in the differentiating of malignant and benign thyroid nodules by using fine needle aspiration biopsy cytology criteria as a reference standard. The apparent diffusion coefficient (ADC) values of the normal-looking thyroid parenchyma were also evaluated both in normal patients and in patients with nodules.
  
  
  METHODS
  Between March 2007 and February 2008, 76 consecutive patients with ultrasound-diagnosed thyroid nodules and 20 healthy subjects underwent diffusion-weighted MR imaging by using single-shot spin echo, echo planar imaging. A total of 93 nodules were included in the study using the following b factors 100, 200, and 300 mm(2)/s. ADC values of thyroid nodules and normal area in all subjects were calculated and compared using suitable statistical analysis.
  
  
  RESULTS
  Mean ADC values for malignant and benign nodules were 0.96+/-0.65 x 10(-3) and 3.06+/-0.71 x 10(-3)mm(2)/s for b-100 factor, 0.56+/-0.43 x 10(-3) and 1.80+/-0.60 x 10(-3)mm(2)/s for b-200, and 0.30+/-0.20 x 10(-3) and 1.15+/-0.43 x 10(-3)mm(2)/s, for b-300, respectively. Mean ADC values of malignant nodules were lower than benign nodules. There were significant differences in ADC values between benign and malignant nodules. ADC values among normal-appearing thyroid parenchyma of patients and normal-appearing thyroid parenchyma of healthy subjects were insignificant at all b factors.
  
  
  CONCLUSIONS
  Benign nodules have higher ADC values than malignant ones. DWI may be helpful in differentiating malign and benign thyroid nodules.
authors.affiliation: Department of Radiology, Faculty of Medicine, Firat University, Elazig, Turkey. bozgeyik4@hotmail.com
authors.forename: Zulkif
authors.initials: Z
authors.lastname: Bozgeyik
authors.forename: Sonay
authors.initials: S
authors.lastname: Coskun
authors.forename: A Ferda
authors.initials: AF
authors.lastname: Dagli
authors.forename: Yusuf
authors.initials: Y
authors.lastname: Ozkan
authors.forename: Fatih
authors.initials: F
authors.lastname: Sahpaz
authors.forename: Erkin
authors.initials: E
authors.lastname: Ogur
mesh_terms: D000328:Adult; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016606:Thyroid Nodule / Q000175:diagnosis*