Imaging Studies

The options available for the imaging of parotid neoplasms include plain films, sialography, ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) scanning. Considerations of cost-effectiveness have placed increasing pressure on physicians to pursue imaging studies that are most likely to be useful on the basis of the presumed pathology after careful history and physical examination. It appears that CT scanning is the most widely accepted and routine form of imaging for parotid neoplasms3'7 because it permits assessment of the entire parotid gland, the parapharyngeal space, the mandible, the skull base, and the mastoid region.

Some radiologists disagree with this approach and believe that the MRI gives more valuable information because it is more sensitive than CT for soft tissue lesions.8-12

A few experts feel rather strongly that the routine use of CT or MRI is not cost-effective and that it should not be recommended, even though they concede that useful information can be obtained from these studies in certain situations. They believe that the use of CT or MRI should be restricted to patients with recurrent neoplasms, high suspicion of malignancy, very large neoplasms, suspected parapharyngeal space involvement, suspected carotid artery involvement, or any other finding that introduces the possibility of inoperability.13

Parotid neoplasms in children are a special case, even though they are uncommon. We know that about 50% of these neoplasms in infants will be hemangiomas and that they usually present within the first few months of life. The CT scan is not helpful in this diagnostic situation. The first attempt at imaging should be to obtain plain films, as these will sometimes show calcifications that will strongly suggest that the tumor is a hemangioma. If the plain films are negative and there is a need for diagnostic precision, the use of technetium 99-labeled red blood cells can provide nearly 100% specificity for diagnosing hemangioma if the imaging demonstrates poor activity in the profusion phase with gradual uptake in the early pool images and increased uptake in the delayed scan.14

In my experience, the controversy is usually a moot point, as patients usually present in our office carrying a CT scan under their arm at the time of our initial contact. Once this controversy has been resolved, it will be important to educate primary care physicians concerning the most appropriate imaging studies to be requested.

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