Background & objective: Because (18)F-FDG PET/CT can display cancer lesion morphology, size and the relatinship of the cancer lesion to adjacent tissues, it is used in the diagnosis and classification of nasopharyngeal carcinoma (NPC). This study was to explore the application value of (18)F-FDG PET/CT in TNM staging by comparing the performance of MRI and PET/CT together with pathological results for some small lymph nodes.
Methods: Sixty-eight pathologically proven NPC patients were selected from Sep.2005 to Mar. 2007 in Sun Yat-sen University Cancer Center. All cases underwent both MRI and (18)F-FDG PET/CT examinations. PET/CT two-dimensional (2D) data were collected. Automatic dose tracking scanning and contrast-enhanced CT scanning were performed. (18)F-FDG was intravenously administrated at a dose of 3.7-5.5 MBq/kg. MRI T1W, T2W and T1W Gd-DTPA enhanced images were obtained. Neck lymph nodes of 10 NPC patients were pathologically examined.
Results: Nasopharyneal lesions of all 68 cases were all clearly displayed by both PET/CT and MRI. Among 138 small lymph nodes smaller than 1cm in diameter, which were positively detected by PET/CT, only 28.0% were suggested questionable by MRI scanning. Fourteen out of sixteen (87.5%) positive lymph nodes detected by PET/CT from 10 patients were pathologically confirmed. Both PET/CT and MRI revealed enlarged lymph nodes of the neck. Some lymph nodes whose proliferation was inhibited during radiotherapy suggested by PET/CT were displayed intensified images by contrast-enhanced PET/CT and MRI. Metastases to lung, bone and liver in eight stage IVb patients were clearly displayed by PET/CT, but not by MRI. The stage of 24 patients was adjusted after PET/CT scanning.
Conclusions: (18)F-FDG PET/CT with automatic dose tracking scanning protocol and contrast-enhanced scanning can provide more comprehensive information than MRI in diagnosing and staging NPC.