Role of diffusion-weighted magnetic resonance imaging in the differentiation of parotid gland tumors

Objectives The aim of this study was to assess the role of magnetic resonance diffusion-weighted imaging (DWI) in the characterization of parotid gland tumors using different b values. Methods Thirty-six patients with 41 parotid masses were included in this prospective study. DWI images were obtained using three different b values (100, 500, and 1000 s/mm 2 ). The final diagnosis was made by fine-needle aspiration cytology or histopathological examination. The mean apparent diffusion coefficient (ADC) values of benign lesions versus malignant lesions, pleomorphic adenoma versus Warthin’s tumor, pleomorphic adenoma versus malignant lesions, and Warthin’s tumor versus malignant lesions were compared using the ADC values obtained with b = 500 and b = 1000 s/mm 2 . When significant differences were found for these comparisons, cutoff points were determined by receiver-operating characteristic curve analysis. Results The mean ADC value of benign lesions ( n = 32) was significantly higher than that of malignant lesions ( n = 9). The mean ADC value of pleomorphic adenoma was significantly higher than that of both Warthin’s tumor and malignant tumors. No significant differences between the ADC values of Warthin’s tumor and malignant tumors were detected. Conclusions DWI with both b = 500 and b = 1000 s/mm 2 may be helpful for the distinction between pleomorphic adenoma and Warthin’s tumor, and between pleomorphic adenoma and malignant tumors, but is not efficient for the differentiation of Warthin’s tumor from malignant tumors.