Differentiation of Recurrent Tumor and Posttreatment Changes in Head and Neck Squamous Cell Carcinoma: Application of High b-Value Diffusion-Weighted Imaging

BACKGROUND AND PURPOSE: High b-value DWI has been expected to have an additional diagnostic role and demonstrated some promising results in head and neck cancer. The aim of this study was to evaluate the diagnostic performance of DWI at a high b-value (b=2000 s/mm²) compared with a standard b-value (b=1000 s/mm²) and the ratio of ADC values of high and standard b-values for their ability to differentiate between recurrent tumor and posttreatment changes after the treatment of head and neck squamous cell carcinoma.

MATERIALS AND METHODS: A total of 33 patients diagnosed with head and neck squamous cell carcinoma were enrolled in the present study; all had contrast-enhancing lesions on follow-up MR imaging. All patients underwent single-shot echo-planar DWI at b=1000 s/mm² and b=2000 s/mm², and corresponding ADC maps were generated (ADC₁₀₀₀ and ADC₂₀₀₀, respectively). The mean ADC₁₀₀₀, ADC₂₀₀₀, and ADC_ratio (ADC_ratio = ADC₂₀₀₀/ADC₁₀₀₀ × 100) values were evaluated within a manually placed ROI with contrast-enhanced T1-weighted images as references. For the statistical analysis, we performed a Student t test and multivariate logistic regression.

RESULTS: The mean ADC₁₀₀₀ in recurrent tumor was significantly lower than that in posttreatment changes (P < .001), whereas the mean ADC₂₀₀₀ resulted in no significant difference (P = .365). The mean ADC_ratio was significantly higher in recurrent tumor than that in posttreatment changes (73.5 ± 7.2% vs 56.9 ± 8.8%, respectively; P < .001). Multivariate logistic regression analysis revealed that the ADC_ratio was the only independently differentiating variable (P = .024). The sensitivity, specificity, and accuracy of ADC_ratio were 95.0%, 69.2%, and 84.8%, respectively, by use of the optimal cutoff value of 62.6%.

CONCLUSIONS: We suggest that the ADC_ratio calculated from the ADC₁₀₀₀ and ADC₂₀₀₀ is a promising value for the differentiation of recurrent tumor and posttreatment changes in head and neck squamous cell carcinoma.