Figure 6c. Primary tumor of the larynx in a 45-year-old man with epiglottic carcinoma who was referred for presurgical evaluation. Axial CT (a), PET (b), and PET-CT fusion (c) images show a focus of uptake (arrow) that corresponds to a mass that originates from the larynx and nearly obliterates the lumen on the CT scan. Correlation with CT and PET-CT helped greatly in establishing the diagnosis of primary laryngeal malignancy rather than activated laryngeal muscles. In cases of occult head and neck tumor, differentiation may be difficult without CT correlation. It is essential that the patient remain silent during the period of FDG uptake.