MRI of the parapharyngeal space.

Magnetic resonance imaging has replaced contrast-enhanced CT as the primary imaging modality for parapharyngeal space masses. It has several advantages over CT. MRI's superior contrast resolution enables the imager to better define normal anatomic structures and establish more precise tumor margins. Magnetic resonance's direct multiplanar imaging capability allows the diagnostician to offer his clinical colleagues a more accurate assessment of the total extent (in three dimensions) of disease and a better map of the spatial relationship of tumors to crucial vessels. This important information aids the clinician in making better informed decisions concerning the appropriate treatment plan (surgery versus radiation, surgical approach, radiation ports). Magnetic resonance's major inadequacy, compared with CT, is suboptimal detection of calcifications and subtle bony changes. Because of this, there are clinical situations when both MRI and CT are required, either to make a more definitive diagnosis or to include (exclude) certain pathology in (from) the differential diagnosis. Although there is considerable overlap in the signal intensity of various lesions, it probably is beyond realistic expectations to seek complete tissue specificity from any imaging tool. Hopefully, MRI spectroscopy will enable us, as imagers, in combination with our basic science colleagues, to take that giant step forward.