Prevalence + patterns of physiologic muscle uptake detected with whole-body PE

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Prevalence and patterns of physiologic muscle uptake detected with

whole-body PET

http://www.news-medical.net/?id=16529

Muscle activity - from turning a page in a book to shoveling snow -

impacts positron emission tomography results, says study in journal

of nuclear medicine technology.

Before you take that walk or ride a bike, think again-especially if

you will be undergoing a positron emission tomography (PET) scan any

time soon.

" Any type of physical activity-from tapping your feet while in the

waiting room to jogging the neighborhood the day before-can affect

the results of a PET scan and lead to false-positive results, " said

Medhat M. Osman, M.D., ScM, 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. " Knowing whether a patient has participated in physical activity

is relevant in interpreting a PET imaging study, " added the co-author

of " Prevalence and Patterns of Physiologic Muscle Uptake Detected

With Whole-Body 18F-FDG PET, " which appears in the March issue of the

Journal of Nuclear Medicine Technology.

" Individuals undergoing PET scans should take it easy-and if you do

any kind of physical activity outside of the ordinary-you should let

your nuclear medicine technologist know so it can be noted, " said

C. Schlarman, MBA, CNMT, educational coordinator with the

department of nuclear medicine technology at St. Louis University.

Physical activity may trigger a potential source of false-positive

results on a PET scan in about one out of eight patients, he noted.

In order to obtain the most accurate reading of PET scans, patients

should not exercise excessively 48 hours prior to having a PET scan

and should remain quiet prior to scanning, Schlarman said.

PET is a powerful medical imaging procedure that noninvasively

demonstrates the function of organs and other tissues. It is used

primarily as a diagnostic tool in oncology, cardiology, neurology and

many other medical specialties. To image cancer, a

radiopharmaceutical such as fluorodeoxyglucose (FDG), which includes

both sugar (metabolized at a higher rate by cancer cells) and a

radionuclide, is injected into the patient. Because cancer cells

metabolize sugar at higher rates than normal cells, the

radiopharmaceutical is drawn in higher concentrations

(called " uptake " ) to cancerous areas. The PET scan shows where the

radiopharmaceutical is by tracking the gamma ray signals given off by

the radionuclides. PET scans are very sensitive, and increased

physical activity can create problems in differentiating between

normal and pathologic uptake, explained Osman. Normal muscles

accumulate little FDG, but muscles exercised just before or around

the time of the scanning can exhibit intense uptake into those

muscles-for example, possibly mimicking cancer, he added.

The study advises technologists to instruct patients to minimize

muscle activity during the uptake phase and to telephone patients

ahead of their appointments to advise them to refrain from any

excessive muscle activity at least 48 hours before a PET scan. The

study's findings emphasize that the accuracy of studies for patients

can be improved through educating technologists of the relationship

between muscle activity and uptake and in coordinating a team

approach with physicians, said Schlarman. " Technologists play a major

role in informing physicians of patients' activity " that could skew

the reading of their PET scans, Osman said. " Any unexpected or

unexplained excessive muscle uptake should initiate communications

between technologists and reading physicians to avoid false-positive

PET scan interpretations, " he added.

The team of technologist and physician researchers in St. Louis-all

SNM or SNM Technologist Section members-studied the whole-body PET

scans of more than 1,100 cancer patients over a one-year period. Of

those patients, nearly 13 percent had excessively increased muscle

uptake on the PET scan that matched technologists' notes of muscle

activity during the uptake phase or prior to scanning. Increased

uptake was seen in individuals' head and neck, thorax and upper

extremities, indicating the influence of activities such as raising

one's head while on a stretcher, writing or turning the pages of a

book, shoveling snow or pushing a wheelchair.

http://www.snm.org