Posttreatment imaging of the nasopharynx.

Nasopharyngeal carcinoma (NPC) is the most common epithelial tumor of the nasopharynx. Radiation therapy is the mainstay of treatment while surgery or chemotherapy is used in selected patients. NPC usually regresses after 3 months of radiation therapy. Nonetheless, a residual mass may be present following treatment and this does not necessarily indicate viable tumor. Imaging studies are often used in conjunction with clinical examination following treatment. While computed tomography (CT) is widely used due to its greater availability, less expensive, and less time consuming, MR imaging is now becoming the preferred modality. MR imaging is more capable than CT for identifying mature scarring, tumor recurrence and postradiation complications. However, MR imaging cannot reliably demonstrate mucosal recurrence or differentiate tumor recurrence from postradiation tissue changes. Familiarity with the imaging findings of various posttreatment changes, tumor recurrence and postradiation complications is essential for management of NPC. Comparison with previous images or imaging-guided biopsy facilitates definitive diagnosis.