You might want to think twice before taking a walk or riding your bike, particularly when you’re due for a positron emission tomography (PET) scan in the near future.

Take time to think before you go for a walk or ride a bike-especially if you have any plans to undergo positron emission tomography (PET) scans Medhat M. said that any form of physical activity-from tapping your toes in the waiting room to jogging around the neighborhood the day before-can affect the results of a PET scan and lead to false-positive results. Theodore Asman, MD, ScM, PhD, is an assistant professor in the department of internal medicine’s division of nuclear medicine and professor of PET at the St. Louis University Hospital in Missouri. Physical activity participation has direct implications for the interpretation of PET imaging studies, said the co-author of “Prevalence and Patterns of Physiologic Muscle Uptake Detected With Whole-Body 18F-FDG PET,” which is published in the journal

Individuals who undergo PET scans should ease up on physical activity before their scans, and if they engage in any outside of their normal routine, they must inform their nuclear medicine technologists so it can be noted, The educational coordinator for the department of nuclear medicine technology at St. Louis University is Dr. Scott Schlarman, MBA, CNMT. The use of physical activity around one out of eight times may result in false-positive results on PET scans, the professor According to Schlarman, patients undergoing PET scans should not exercise excessively 48 hours before the scan and not talk on a cell phone during the scan. PET imaging is a powerful tool that can demonstrate organ function in oncology, cardiology, neurology, and other In order to image cancer, a radiopharmaceutical known as fluorodeoxyglucose (FDG) that combines a sugar (metabolized at a high rate by cancer cells) with a radionuclide is administered to As cancer cells metabolize sugar much more quickly than normal cells, the radiopharmaceutical becomes absorbed into the cancerous tissues in higher concentrations (known as the “uptake” factor). Through tracking the gamma ray signals given off by the radionuclides, the PET scan shows the location of the radiopharmaceutical. The PET scan is very sensitive, and an increase in physical activity can create problems when it comes to distinguishing normal from pathologic uptake, said In normal muscles, FDG uptake is relatively low. However, muscles that are worked just before or around the time of the scan may display intense uptake, possibly reflecting cancer, according to him.

Researchers recommend that technologists instruct the patients not to engage in excessive muscle activity during the uptake phase and to telephone patients ahead of their appointments to request they refrain from excessive muscle activity at least 48 hours in advance of the Educating technologists about the relationship between muscle activity and uptake, along with working actively with physicians, Schlarman says, will improve the accuracy of studies for patients, and this can be implemented by coordinating a team approach with them. The job of technologists is to inform physicians of possible abnormal activity in patients that could lead to incorrect readings of their PET scans, Dr. Osman said. “Any unexpected or unexplained excessive muscle uptake should initiate communication between technologists and reading physicians,” he said. A team of medical technology and physician researchers from St. Louis-all members of SNM or the SNM Technologist Section-analyzed more than 1,100 whole-body PET scans taken over one year from more than 1,100 cancer patients. Thirty-three percent of patients with this propensity had excessively hyperkinetic muscle activity on the PET scan. This was confirmed by the technologists’ note that muscle activity occurred during the uptake phase or before the examination began. The uptake of the imaging signal was increased in the head and neck, thorax, and upper extremities of individuals during activities such as raising one’s head while on a stretcher, writing, turning pages of a book, shoveling snow, or driving Besides Osman and Schlarman, Ryan S., and Bruce N. Johnson also contributed to the manuscript “Prevalence and Patterns of Physiologic Muscle Uptake Detected with Whole-Body 18F-FDG PET.”. Dr. J. S. Jackson, division of nuclear medicine, department of internal medicine, St. Louis University School of Medicine, St. Louis, Mo., and Dr. L. William Crawford. I.Hubble, MHA, Department of Nuclear Medicine Technology, College of Health Sciences, St. Louis University, St. Louis, Missouri.