18F-fluoroethylcholine PET/MR imaging in salivary adenoid cystic carcinoma

Abstract

Adenoid cystic carcinomas (ACCs) are rare tumors arising in the head and neck area and are characterized by a marked tendency for perineural invasion often causing incomplete resection and multiple recurrences. In some cases identifying of recurrences is challenging and in addition to the commonly used magnetic resonance imaging (MRI), a metabolic imaging method such as positron-emission-tomography (PET) could be helpful to differentiate between scar formation, radiation necrosis or vital tumor recurrence. Well established in oncological imaging is PET using 18F-fluorodeoxyglucose (FDG). But the close neighborhood to the brain and its high physiologic uptake may hamper the delineation of the tumor using FDG. 18F-fluoroethylcholine (FEC) is an oncologic tracer with negligible cerebral uptake.

This case report presents in addition to a FDG-PET/computed tomography (CT) for the first time images using FEC for PET/MRI performed with an integrated PET/MR (Biograph mMR®, Siemens Healthcare) in a patient with ACC. The FEC-PET/MRI of the head and neck reveals tumor recurrence with focal intense tracer uptake in the temporal lobe proving infiltration and precise tumor delineation on the contrast-enhanced T1 weighted MRI. Compared to FDG-PET and CT, FEC-PET/MRI might offer an improved metabolic imaging in ACC.