High Field MRI in Parotid Gland Tumors: A Diagnostic Algorithm.

Backgrounds: Imaging of parotid tumors is crucial for surgery planning, but it cannot distinguish malignant from benign lesions with absolute reliability. The aim of the study was to establish a diagnostic MRI algorithm to differentiate parotid tumors. Methods: A retrospective study was conducted including all patients with parotid tumors, who underwent 3T-MRI and surgery. Morphological characteristics and normalized T2 and late postcontrast T1 signal intensities (SI) were assessed. "Ghosting sign" on late postcontrast T1 sequence was defined as indistinguishability of the tumor except for a thin peripheral enhancement. Patients were divided according to histology and imaging data were compared. A diagnostic MRI algorithm was established. Results: Thirty-six patients were included. The combination of normalized late T1 postcontrast SI, normalized T2 SI and "ghosting sign" allowed for the distinguishing of malignant from benign parotid tumors with high sensitivity (100%), specificity (93%), positive predictive value (80%), negative predictive value, (100%) and accuracy (94%). Moreover, pleomorphic adenomas often showed a homogeneous T2 signal and a complete capsule (p < 0.01), Warthin tumors protein-rich cysts and calcifications (p < 0.005 and p < 0.05), and malignant tumors an inhomogeneous contrast enhancement (p < 0.01). Conclusions: High field MRI represents a promising tool in parotid tumors, allowing for an accurate differentiation of malignant and benign lesions.