1.5 T MR in the diagnosis of parotid masses: comparison with ultrasonography

Twenty-two patients who presented with laterocervical retromandibular enlargement were examined with both US and MR imaging to assess the intrinsic/extrinsic relationship of the mass to the parotid gland, the involvement of the facial nerve and adjacent structures, as well as the nature of the mass. Both US and MR imaging proved to be poorly specific in the characterization of the inflammatory lesions. Within the mass, both methods revealed high sensitivity (100%) in identifying the lesions, even very small ones. MR imaging allowed the lesion to be accurately located, the facial nerve to be identified, and its possible infiltration to be evaluated, with higher reliability than US, thanks to its higher contrast resolution and to its multiplanarity. Neither US nor MR imaging allowed the benign/malignant nature of the lesion to be assessed. On the basis of their experience, the authors suggest the use of T2-weighted MR sequences, with long TR and TE, to differentiate pleomorphic adenomas from other histotypes, after US assessment of the solid nature of parotid masses.