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Foods to Eat Before a PET Scan. A PET (positron emission tomography) scan is a powerful process for detecting cancer. Cancer cells grow extremely fast and need a lot of glucose. A doctor will inject the patient with glucose, and the PET scanner detects if any cells are emitting signs of high glucose use. If you eat before your PET scan, you risk throwing your glucose levels off balance and getting inaccurate results.
Most PET scans today are performed with an imaging radiopharmaceutical -- most commonly FDG (Fluorodeoxyglucose), which is a tracer that goes into the heart to provide a picture of the organ's function on PET scans. If a person exercises before having a PET/CT scan, more FDG appears in the heart region, obscuring the view. The researchers found that the same thing happens with caffeine: The heart beats faster when you drink coffee, just as it does when you exercise.