Long-lasting FDG uptake in the muscles after strenuous exercise

Area of Science:

• Nuclear Medicine
• Radiology
• Medical Imaging

Background:

• Current guidelines for Fluorodeoxyglucose (FDG) Positron Emission Tomography/Computed Tomography (PET/CT) mandate exercise cessation 24 hours before imaging.
• Skeletal muscle uptake of FDG can be influenced by physiological factors, including physical activity.

Observation:

• A 15-year-old male adolescent presented for an FDG PET/CT scan.
• The patient reported engaging in vigorous physical activity approximately 4 days before the scan appointment.

Findings:

• The FDG PET/CT scan revealed unexpectedly intense focal and diffuse skeletal muscle uptake.
• This intense uptake was observed despite the exercise occurring several days prior to FDG administration, deviating from the standard 24-hour guideline.

Implications:

• This case demonstrates that significant skeletal muscle FDG activity can persist longer than anticipated after strenuous exercise.
• Physicians interpreting FDG PET/CT scans should consider recent physical activity, even if it falls outside the typical 24-hour window, when evaluating muscle uptake.
• Further investigation may be warranted to understand the duration and intensity of exercise-induced FDG uptake in skeletal muscle.