Plain radiography and sialography are useful for ductal inflammatory disease, but computed tomography (CT), ultra-sonography, CT sialography, and magnetic resonance imaging (MRI) are usually better for evaluation of suspected neoplastic disease. MRI is particularly useful when inflammatory disease is not suspected. It does not have the risks of radiation exposure nor complications with intraductal injection of contrast media, and it is often superior in demonstrating the interface of tumour and surrounding tissues. T1-weighted images of normal parotid have an image signal intermediate between fat and muscle whereas submandibular tissue is closer to muscle in intensity. With advanced age and fatty infiltration, the signal intensity of parotid tissue approaches fat. Most salivary gland tumours are brighter on T2 than T1 images but this difference is minimal in prominently cellular tumours. Lesions with higher water content, such as human immunodeficiency virus related parotid cysts, Warthin tumours, cystadenomas and cystadeno-carcinomas, and cystic mucoepidermoid carcinomas, have a bright T2 signal.
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