RESUMEN
<p><b>OBJECTIVE</b>To compare the clinical significance of PET/CT and MRI in diagnosing lymph node metastasis and N staging of nasopharyngeal carcinoma (NPC).</p><p><b>METHODS</b>116 NPC patients had undergone PET/CT and MRI before therapy. The findings of PET/CT and MRI in diagnosing lymph node metastasis and N staging were compared according to the results of follow-up.</p><p><b>RESULTS</b>A total of 614 lymph nodes in 116 patients were analyzed. 340 positive nodes and 274 negative nodes interpreted by image findings were verified during follow-up. The sensitivity, specificity and accuracy of PET/CT in diagnosing node metastasis was 93.2%, 98.2% and 95.4%, while that of MRI was 88.8%, 91.2% and 89.9%, respectively, with statistically significant difference in each between PET/CT and MRI (P < 0.05). Based on Fuzhou Staging System, 109 patients (94.0%) were correctly staged by PET/CT, and 103 patients (88.8%) by MRI, while according to UICC Staging System, 108 patients (93.1%) were correctly staged by PET/CT, and 100 patients (86.2%) by MRI.</p><p><b>CONCLUSION</b>PET/CT is superior to MRI in diagnosing lymph node metastasis and N staging of nasopharyngeal carcinoma. The false-positive and false-negative assessment based on PET-CT scan findings may be caused by: (1) inflammatory hyperplastic node; (2) node with large areas of necrosis; (3) node in diameter less than spatial resolution limitation of PET.</p>