Patients undergoing PET/CT may want to pass on that cup of coffee, according to SNMTS study

06/16/05

Results show caffeine interferes with image results for known or suspected cancers

TORONTO, Canada--Patients who need a positron emission tomography (PET)/computed tomography (CT) procedure to evaluate potential known or suspected malignancies should forgo coffee before the test, according to the results of study released at the Society of Nuclear Medicine's 52nd Annual Meeting June 18–22 in Toronto.

"It is advisable for patients to stop caffeine intake for a 24-hour period prior to imaging," said SNM member Medhat M. Osman, M.D., Sc.M., Ph.D., assistant professor in the department of internal medicine's division of nuclear medicine and director of PET at St. Louis University Hospital, St. Louis, Mo. The study, "Correlation Between Myocardial Uptake and Caffeine Intake: Detection With FDG PET/CT," traced the relationship between caffeine intake and myocardial uptake detected by whole-body PET/CT.

PET is a powerful medical imaging modality that noninvasively (nonsurgically) uses special imaging systems and radioactive tracers to produce pictures of the function and metabolism of the cells in the body. CT is an X-ray test that generates a detailed view of the anatomy or structure of organs and tissues in the body. Fused together, PET and CT images can more accurately define a host of diseases processes than can conventional, anatomic-based imaging alone (such as CT and MRI) and can play an important role in cardiac and neurologic imaging.

Most PET scans today are performed with an imaging radiopharmaceutical--most commonly FDG (fluorodeoxyglucose)--that can be tracked by a PET scanner. Where FDG goes in the heart--its uptake into an organ, a tissue, a cell or body fluids--provides a picture of the heart's function. If a person exercises before having a PET/CT scan, more FDG uptake is noted. 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. Patients who had coffee before their scans had a "significantly higher" myocardial uptake than those with low or no caffeine intake, said Osman. Even average caffeine consumption "may directly affect myocardial uptake," he added.

This is a problem, because an increase in the FDG seen on a scan makes it more difficult to see lesions or read the image if they are in close proximity to the heart, said Osman. By avoiding caffeine and exercise, an individual has a better chance of providing a "good view" of his or her body.

Authors of "Correlation Between Myocardial Uptake and Caffeine Intake: Detection With FDG-PET/CT" are Stephanie M. Anastas, Crystal D. Botkin and Penny E. Yost, all internal medicine, division of nuclear medicine, St. Louis University Hospital, St. Louis, Mo.; Dorina Kallogjeri, Cancer Center Operations; and Medhat M. Osman, internal medicine, division of nuclear medicine, St. Louis University Hospital, St. Louis, Mo.

Source: Eurekalert & others

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