[F-18]FDG imaging of head and neck tumors: Comparison of hybrid PET, dedicated PET and CT

Aim: Aim of the study was to evaluate [F-18] FDG imaging of head and neck t umors using a Hybrid-PET device of the 2nd or 3rd generation. Examinations were compared to dedicated PET and Spiral-CT. Methods: 54 patients sufferin g from head and neck tumors were examined using dedicated PET and Hybrid-PE T after injection of 185-350 MBq [F-18] FDG. Examinations were carried out on the dedicated PET first followed by a scan on the Hybrid-PET. Dedicated PET was acquired in 3D mode, Hybrid-PET was performed in list mode using an axial filter. Reconstruction of data was performed iteratively on both, de dicated PET and Hybrid-PET. All patients received a CT scan in multislice t echnique. All finding have been verified by the goldstandard histology or i n case of negative histology by follow up. Results: Using dedicated PET the primary or recurrent lesion was correctly diagnosed in 47/48 patients, usi ng Hybrid-PET in 46/48 patients and using CT in 25/48 patients. Metastatic disease in cervical lymph nodes was diagnosed in 17/18 patients with dedica ted PET, in 16/18 patients with Hybrid-PET and in 15/18 with CT. False posi tive results with regard to lymph node metastasis were seen with one patien t for dedicated PET and Hybrid-PET, respectively, and with 18 patients for CT. In a total of I I patients unknown metastastic lesions were seen with d edicated PET and with Hybrid-PET elsewhere in the body. Additional malignan t disease other than the head and neck tumor was found in 4 patients. Concl usion: Using Hybrid-PET for [F-18] FDG imaging reveals a loss of sensitivit y and specificity of about 1-5% as compared to dedicated PET in head and ne ck tumors, [F-18] FDG PET with both, dedicated PET and Hybrid-PET is superi or to CT in the diagnosis of primary or recurrent lesions as well as in the assessment of lymph node involvement.