Total Eclipse of FDG-PET Scan Caused by Hyperphysiological FDG Uptake of Masticatory Muscles Due to Chewing

In routine oncological 18F-fluorodeoxyglucose positron emission tomography (FDG-PET/CT) scan, the patients rest in a quite, dimly lit room for 60 minutes after intravenous (IV) injection of FDG and they are instructed not to move during this time (uptake phase) before FDG-PET/CT scanning to prevent and decrease unwanted FDG accumulations on muscle traces caused by muscle movements. In conditions of patient inconsistency, undesirable activities can be seen and reach high levels making difficult or even impossible to interpret the images. Different muscle groups form various physiological or over- physiological uptake patterns depending on their specific motion. Herein we represent a good didactic example to this phenomenon.