[18F]FDG imaging of head and neck tumours: comparison of hybrid PET and morphological methods.

The aim of this study was to evaluate fluorine-18 fluorodeoxyglucose ([(18)F]FDG) imaging of head and neck tumours using a second- or third-generation hybrid PET device. Results were compared with the findings of spiral computed tomography (CT) and magnetic resonance imaging (MRI), and, as regards lymph node metastasis, the ultrasound findings. A total of 116 patients with head and neck tumours (83 males and 33 females aged 27-88 years) were examined using a hybrid PET scanner after injection of 185-350 MBq of [(18)F]FDG (Picker Prism 2000 XP-PCD, Marconi Axis gamma-PET(2) AZ). Hybrid PET examinations were performed in list mode using an axial filter. Reconstruction of data was performed iteratively. Ninety-six patients underwent CT using a multislice technique (Siemens Somatom Plus 4, Marconi MX 8000), 18 patients underwent MRI and 100 patients were examined by ultrasound. All findings were verified by histology, which was considered the gold standard, or, in the event of negative histology, by follow-up. Correct diagnosis of the primary or recurrent lesion was made in 73 of 85 patients using the hybrid PET scanner, in 50 of 76 patients on CT and in 7 of 10 patients on MRI. Hybrid PET successfully visualised metastatic disease in cervical lymph nodes in 28 of 34 patients, while 23 of 31 were correctly diagnosed with CT, 3 of 4 with MRI and 30 of 33 with ultrasound. False positive results regarding lymph node metastasis were seen in three patients with hybrid PET, in 14 patients with CT and in 13 patients with ultrasound. MRI yielded no false positive results concerning lymph node metastasis. In one patient, unrecognised metastatic lesions were seen on hybrid PET elsewhere in the body (lung: n=1; bone: n=1). Additional malignant lesions at sites other than the head and neck tumour were found in three patients (one patient with lung cancer, one patient with pelvic metastasis due to a carcinoma of the prostate and one patient with pulmonary metastasis due to breast cancer). It is concluded that [(18)F]FDG PET with hybrid PET scanners is superior to CT and MRI in the diagnosis of primary or recurrent lesions as well as in the assessment of lymph node involvement, whereas it is inferior to ultrasound in the detection of cervical lymph node metastasis.