title: Diffusion-weighted imaging to differentiate metastatic from non-metastatic retropharyngeal lymph nodes in nasopharyngeal carcinoma.
abstract: OBJECTIVE
  To evaluate the diagnostic value of diffusion-weighted MRI for differentiating metastatic from non-metastatic retropharyngeal lymph nodes (RLNs) in patients with nasopharyngeal carcinoma (NPC).
  
  
  METHODS
  Untreated patients with NPC (n = 145) were scanned with both morphological MRI and diffusion-weighted imaging (DWI). RLNs (n = 335) were classified as metastatic on the basis of response to therapy as assessed on follow-up MRI. Morphological (short- and long-axial diameters) and functional [mean apparent diffusion coefficient (ADC) and minimum ADC values] parameters of the RLNs were derived from DWI and compared between metastatic and non-metastatic groups. A receiver operating characteristic curve and the area under the curve were used to evaluate the effectiveness of individual criteria and to generate threshold values to diagnose RLN metastases.
  
  
  RESULTS
  Statistically significant differences between metastatic and non-metastatic RLNs were found for all four parameters derived from DWI (p < 0.001). At threshold values, accuracies of the ADC-based criteria (0.938 and 0.965 for mean and minimum ADC values, respectively) were greater than that of size-based criteria (0.838 and 0.809 for short- and long-axial diameters). The minimum ADC value at the threshold of 0.89 × 10(-3) mm(2) s(-1) was the most effective of all parameters in differentiating metastatic from non-metastatic RLNs with the sensitivity of 95.7%, specificity of 95.1% and accuracy of 96.5%.
  
  
  CONCLUSIONS
  DWI is feasible for differentiating metastatic RLNs from non-metastatic nodes in patients with NPC with high accuracy, and the minimum ADC derived from DWI could serve as a standard clinical marker for disease status.
authors.affiliation: 1 State Key Laboratory of Oncology in Southern China, Guangzhou, China.
authors.forename: H
authors.initials: H
authors.lastname: Li
authors.forename: X-W
authors.initials: XW
authors.lastname: Liu
authors.forename: Z-J
authors.initials: ZJ
authors.lastname: Geng
authors.forename: D-L
authors.initials: DL
authors.lastname: Wang
authors.forename: C-M
authors.initials: CM
authors.lastname: Xie
mesh_terms: D000328:Adult; D000368:Aged; D002681:China; D003287:Contrast Media; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000175:diagnosis* / Q000473:pathology; D009333:Neck; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media
keywords: apparent diffusion coefficient (ADC) value; diffusion-weighted imaging (DWI); magnetic resonance imaging (MRI); nasopharyngeal carcinoma; retropharyngeal lymph node (RLN)