Contrast enhancement in head and neck imaging.

Iodinated intravenous contrast material for CT of the extracranial head and neck is extremely useful in almost all clinical settings. Contrast material facilitates visualization of the carotid artery and jugular vein; helps delineate the full extent of neoplastic and inflammatory lesions, and in limited circumstances can suggest a precise diagnosis based on a particular pattern of enhancement. The role of gadolinium is not as clear. Gadolinium chelates are not routinely needed to opacify vessels, and with operator-dependent changes in pulse sequence parameters, contrast between a lesion and normal structures can be maximized. A number of studies, however, have shown that gadolinium can improve detection of perineural or intracranial spread of disease; confirm necrosis within lymph nodes, abscesses, or tumors; and more accurately show the full extent of disease into surrounding soft tissues. It is impossible to predict before imaging which patients will benefit from the addition of MR contrast agents, and for that reason enhanced images are often routinely acquired.