Non-enhanced MRI in combination with color Doppler flow imaging for improving diagnostic accuracy of parotid gland lesions.

PURPOSE: To determine the value of non-enhanced MRI in combination with color Doppler flow imaging (CDFI) for differentiating malignant parotid tumors from benign ones.

METHODS: This retrospective study analyzed 51 parotid gland lesions (39 benign and 12 malignant) in 51 patients who underwent preoperative CDFI as well as non-enhanced MRI including T1 -weighted, T2 -weighted, and diffusion-weighted imaging (DWI). Degrees of intratumor vascularity were categorized into four grades basing on CDFI findings. The relationships between the lesion and its adjacent external carotid artery and retromandibular vein were inspected on T1 -weighted and T2 -weighted images. Apparent diffusion coefficient (ADC) values were calculated from diffusion-weighted images, and were used to classify the parotid gland lesions with and without reference to the CDFI findings. The classification results were compared using the McNemar test. Sensitivity, specificity, and accuracy percentages were calculated when the non-enhanced MRI/CDFI findings were used to differentiate benign lesions from malignant ones.

RESULTS: The diagnostic accuracy (96.1 vs 82.4%) was significantly improved when ADCs were used together with CDFI findings for classifying parotid gland lesions compared to when ADCs were used alone. Pleomorphic adenomas had the highest ADCs. The ADC thresholds were 1.425 × 10-3  mm2 /s for differentiating pleomorphic adenomas from carcinomas, 0.999 × 10-3  mm2 /s for differentiating pleomorphic adenomas from other benign lesions, and 0.590 × 10-3  mm2 /s for differentiating benign lesions other than pleomorphic adenomas from lymphomas.

CONCLUSION: Combining CDFI with non-enhanced MRI can improve the diagnostic accuracy of MRI for classifying parotid gland lesions.