Patients who need PET/CT scans should avoid drinking coffee

Patients who need a positron emission tomography (PET)/computed tomography (CT) procedure to evaluate known or suspected malignancies should lay off the java, according to research by Medhat M. Osman, M.D., Ph.D., assistant professor in the department of internal medicine's division of nuclear medicine and director of PET at Saint Louis University Hospital.

Dr. Osman presented his study at the Society of Nuclear Medicine's annual conference Sunday in Toronto. His research traces the relationship between caffeine intake and myocardial uptake, which is the amount of tracer used during PET/CT that can be detected by the whole-body scans.

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.

This is a problem, because an increase in the FDG in the heart seen on a scan makes it more difficult to see lesions close to the heart, says Dr. Osman. By avoiding caffeine and exercise, an individual has a better chance of providing a "good view" of his or her body's condition.

Patients who had coffee before their scans had a "significantly higher" myocardial uptake than those with low or no caffeine intake, says Dr. Osman. Even average caffeine consumption "may directly affect myocardial uptake," he added.

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