Normal FDG distribution patterns in the head and neck: PET/CT evaluation

PURPOSE: To retrospectively evaluate the distribution of fluorine 18 fluorodeoxyglucose (FDG) in the head and neck region with combined positron emission tomography-computed tomography (PET/CT) in patients with no known abnormality in this region. MATERIALS AND METHODS: The institutional review board allowed a retrospective review of PET/CT images obtained in 78 patients with non-head and neck cancer and waived the requirement for informed consent. The accumulation of FDG in 11 normal head and neck structures was visually and quantitatively assessed retrospectively. Positive rate percentage (PRP) was defined as the sum of the percentages of patients with grade 2 and grade 3 tracer uptake intensity. Standardized uptake values (SUVs) were calculated for quantitative analysis. Mean SUVs were compared between the male and female patients by using the unpaired t test, and the correlation between FDG uptake and patient age was assessed by using the Pearson correlation coefficient test. RESULTS: Intense tracer uptake was usually seen in the palatine tonsils (PRP, 98%; mean SUV, 3.48), soft palate (PRP, 96%; mean SUV, 3.13), and lingual tonsils (PRP, 96%; mean SUV, 3.11). In the inferior concha (PRP, 4%; mean SUV, 1.56), thyroid gland (PRP, 3%; mean SUV, 1.31), and tongue (PRP, 1%; mean SUV, 1.39), uptake was typically minimal. FDG accumulation was variable in the sublingual glands (PRP, 72%; mean SUV, 2.93), spinal cord (PRP, 64%; mean SUV, 2.12), submandibular glands (PRP, 5 3%; mean SUV, 2.11), parotid glands (PRP, 51%; mean SUV, 1.90), and vocal cords (PRP, 19%; mean SUV, 1.77). The mean normal-tissue SUV in the soft palate was higher in male than in female patients (P < .01). A negative correlation between age and physiologic FDG uptake was seen in the palatine tonsils (r = -0.51, P < .001) and sublingual glands (r = -0.70, P < .001). CONCLUSION: Intense FDG uptake was usually observed in the palatine tonsils, lingual tonsils, and soft palate, whereas uptake in the major salivary glands was variable. (C) RSNA, 2005.