ABSTRACT
At rest, skeletal muscle uptake of 18F-FDG is low, but a er exercise, a signi cant accumulation of 18F-FDG in selected muscle groups may be misleading. For example, in the evaluation of the head and neck, uptake in the muscles of mastication or laryngeal muscles may mimic malignant lesions. erefore, it is important for the patient to avoid strenuous exercise 24 hours prior to 18F-FDG administration and during the uptake phase following 18F-FDG injection, including chewing or talking. Hyperventilation may induce uptake in the diaphragm, and anxiety-induced muscle uptake is o en seen in the trapezius and paraspinal muscles. Muscle relaxants, such as benzodiazepines, may be helpful in anxious patients. 18F-FDG uptake can also occur in metabolically active adipose tissue (brown fat), particularly in young individuals and cold environment. e distribution is usually typical and includes bilateral neck, supraclavicular regions, anterior mediastinum, axillae, paravertebral regions and suprarenal fossae. Temperature control or the administration of beta-blockers reduce brown adipose tissue uptake.
