Researchers at Saint Louis University have suggested that patients going for PET or CT scan should avoid drinking coffee as caffeine intake interferes with PET/CT image results when there is a known or suspected cancers, Dr. Osman from the university presented his study that looks at the relationship between caffeine intake and uptake by the hear of the tracer used in the PET scan called FDG at the Society of Nuclear Medicine's annual conference held this month in Toronto.
Usually the tracer used during the PET/CT scan called fluorodeoxyglucose, or FDG can be detected by the whole-body scans. Exercise caused the heart rate to increase and hence increase its blood flow and hence the tracer increases in the heart region
depriving other areas around heart from uptaking the FDG, hence a cancer close to the heart could be missed. A similar problem takes place when caffeine in the coffee is in circulation just before PET/CT scan. Caffeine is known to increase heart rate. Hence it is best to avoid both exercise and coffee when undertaking PET/CT scans.