Objective: To differentiate between benign from malignant head and neck masses using diffusion-weighted imaging (DWI) and measured the cutoff point of apparent diffusion coefficient (ADC) value.

Materials and Methods: DWI and measured ADC value were performed in 24 patients with head and neck masses at Ramathibodi Hospital from May 2013 to September 2015. The 37 lesions in 24 patients were divided into benign and malignant head and neck masses.

Results: The 30 lesions were malignant and 7 lesions were benign head and neck masses. By visual inspection, DWI can differentiate benign from malignant head and neck masses by 93.3% of sensitivity, 85.5% of specificity, 91.8% of accuracy, 96.6% of PPV and 75% of NPV. Mean ADC values in benign and malignant head and neck masses were 1.126 x 10^-3 mm²/s and 0.973 x 10^-3 mm²/s, respectively, which was no statistical significant difference (p-value of 0.445). The cutoff point of mean ADC value was 1.200x10^-3 mm²/s for differentiation of benign and malignant head and neck masses.

Conclusion: DWI can differentiate benign from malignant head and neck masses qualitatively. It should be applied to MR protocol in the head and neck masses to enhance diagnostic accuracy.

Keywords: DWI (diffusion-weighted imaging), ADC (apparent diffusion coefficient)