FDA loosens regulatory grip on investigational use of MR

Regulators extend limit from 4T to 8T

Guidelines issued by the FDA July 15 have broadened the territory clinical investigators can cover without first getting permission from the watchdog agency. Studies on magnets up to 8T can now be performed without getting an investigational device exemption (IDE). Safety evidence gathered over the last five years led administrators to change their policy, according to the agency, although the FDA is still holding fast to its 4T limit for infants younger than 30 days.

The data were obtained in both human and animal studies. They addressed a range of indicators from basic vital signs to cognitive function 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 4T and 8T to the local internal review boards."

The reexamination was spurred in part by a continuing trend toward higher field MR in both clinical and investigational settings, Zaremba said. With 3T entering routine use and a high probability of clinical 4T and even 7T scanners appearing in greater numbers, the government made the logical leap and declared 8T magnets a "nonsignificant" risk. Other guidelines set in 1997 for specific absorption rate, gradient field rate of change, and sound pressure level remain unchanged.

"This is great news," said Dr. A. Gregory Sorenson, director of the NMR 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 requests just as they do my 3T studies."

MGH is one of two sites operating 7T systems built for human studies by Siemens Medical Solutions. The other is at the Center for Magnetic Resonance Research (CMRR) at the University of Minnesota. Two more are on order.

Philips Medical Systems announced plans at the 2002 RSNA meeting to install 10 7T systems by the end of 2006, and orders for about half are already in hand. One will be installed at Ohio State University as part of the state's Biomedical Structural, Functional, and Molecular Imaging Enterprise (SCAN 6/11/03). The Philips 7T system will be OSU's second ultrahigh-field scanner. An 8T system has been operating at the university for about five years.

Earlier this spring, GE installed a 7T system at the National Institutes of Health, which is scheduled to begin operation in midsummer. GE is also implementing a 9.4T system at the University of Illinois in Chicago. CMRR will likely beat them to the punch, however. The center began installing its own 9.4T system in early May.