Caffeine and exercise can prevent clear PET and CT imaging of heart

13 July 2005

St. Louis, USA. Consumption of caffeine before a positron emission tomography (PET) or computed tomography (CT) scan of the heart can increase the amount of chemical tracer in the heart and obscure the images.

According to research by Dr Medhat M. Osman, Assistant Professor in the Division of Nuclear Medicine, Department of Internal Medicine, and Director of PET at Saint Louis University Hospital, patients who need a positron emission tomography (PET)/computed tomography (CT) procedure to evaluate known or suspected malignancies should not drink coffee. Dr. Osman presented his study at the Society of Nuclear Medicine’s annual conference in Toronto, Canada, in June.

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, the faster heart beats cause more FDG to appear in the heart region, obscuring the view. The research found that caffeine caused the same effect because it increases the rate of heart beat.

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. 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. By avoiding caffeine and exercise, an individual has a better chance of providing a “good view” of their body’s condition.

More information: http://www.slu.edu

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