MR researchers may now perform investigations on scanners up to 8T without FDA permission. The previous guideline, issued in 1997, set the limit at 4T.
Based on safety evidence gathered in the last five years, the FDA issued new guidelines on July 15 for MR investigations. Studies on magnets up to 8T are no longer considered a significant risk, although anything above that threshold still requires an investigational device exemption (IDE) from the FDA.
The agency also made a distinction between neonates and adults, setting the limit at 4T for babies up to 30 days old.
The sites from which data were collected had conducted a number of safety studies in animals and humans, including monitoring vital signs and cognitive tests before and after scanner exposure, said Loren A. Zaremba, Ph.D., a scientific reviewer for the FDA.
?We were satisfied that no new information would be gained by asking sites coming online at these field strengths to repeat these tests,? he said. ?We decided to hand over responsibility for machines operating between 4 and 8 tesla to the local internal review boards.?
In addition, the FDA saw the handwriting on the wall regarding clinical use of high-field scanners, Zaremba said. With 3T already in clinical use and a high probability of clinical 4T scanners becoming clinically available, the government made the logical leap and declared 8T magnets a nonsignificant risk.
?This is great news,? said Dr. A. Gregory Sorensen, director of the HST Martinos Center at Massachusetts General Hospital. ?I no longer have to get an IDE from the FDA to scan subjects at 7T. The internal review board will look at these request just as they do my 3T studies.?
Other guidelines set in 1997 for specific absorption rate, gradient field rate of change, and sound pressure level remain unchanged.
For more information from the Diagnostic Imaging archives:
