Fig. 14
From: FDG-PET/CT pitfalls in oncological head and neck imaging
a Axial PET/CT image demonstrates slight asymmetrical uptake in the anatomic location of the longus colli muscles (arrow) in a patient previously treated by right partial parotidectomy and radiation therapy for a lymphoepithelial SCC of the right parotid gland. Note hypometabolism of the residual right parotid gland (arrowhead) and focal uptake in the left parotid gland. Corresponding axial CECT (b) and contrast-enhanced fat suppressed T1-weighted MR (c) images illustrate a necrotic metastatic retropharyngeal lymph node on the right side (arrows),mistaken on PET/ CT for minor prevertebral muscle activity and therefore yielding a false negative evaluation. Note the diffuse and heterogeneous enhancement of the remaining right parotid gland following surgery and radiotherapy (arrowheads) better depicted on MRI as on CECT. There is no morphological abnormality in the left parotid gland. Left parotid gland uptake seen on PET/CT was attributed to compensatory hyperactivity