Other Imaging Studies Ultrasonography

Ultrasonography has the advantage of being inexpensive, noninvasive, and simple to perform; it is also virtually free of complications.

It can be used to differentiate solid from cystic masses in the parotid gland. Its use is limited by its ability to visualize only relatively superficial masses.12 Its value in evaluating the deep lobe of the parotid and the parapharyngeal space is hampered by the intervening mandibular ramus. Ultrasound guidance may improve the diagnostic accuracy of FNAB in complex masses of the parotid gland.

Color Doppler Sonography

Color duplex scanning is a noninvasive procedure that may be of help in the preoperative assessment of salivary gland tumors.15 Color doppler sonography has been recently used to evaluate the vascular anatomy of the salivary glands. It can distinguish between the physiologic changes that occur during salivary stimulation in normal subjects, and the flow alterations that occur in diseased glands. Specific patterns of peak systolic vascular shifts were described in various pathologic processes including Sjogren's syndrome, pleomorphic adenoma, and malignant tumors.16

Positron Emission Tomography

A recent study evaluated the ability of positron emission tomography (PET) to differentiate benign from malignant lesions of the salivary glands before surgery.17 Salivary gland masses were evaluated in 26 patients, using PET scans after the administration of fluorine-18-fluorodeoxyglucose (FDG). PET findings helped correctly differentiate benign from malignant masses in 69%, but were false-positive for malignancy in 31% of patients. The investigators concluded that FDG PET is not useful in classifying salivary gland tumors as benign or malignant.17

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