Regulators pose potential threat to high-field MR

Concern is growing within the MR community over proposed European Union regulations that would prohibit workers' direct exposure to higher field strength magnets.

The EU Parliament is considering the issue of exposure to electromagnetic fields, following discussion and review by a European Commission working group in July. The proposal, which is subject to change, would prohibit direct exposure of workers' heads and trunks to magnets with a field strength above 2T, due to safety concerns. Exposure to limbs would not be allowed above 5T.

If approved, the regulations could take effect in a few years, making it illegal to enter the bore of any MR system over 2T. Radiographers and engineers often enter the scanners to adjust and maintain equipment.

MR quality control and siting could also be affected. Medical personnel may be required to wear static field dosimetry badges that have yet to be invented, and exposure could be measured in teslas-per-hour. Regulators may insist on increased shielding and the creation of buffer zones to limit public exposure.

Compliance with the regulations could involve engineering changes that would make equipment more expensive to make, buy, install, and operate, said Dr. Roger Ordidge, a professor of physics applied to medicine at University College London, which operates a 4.7T MR system for research purposes. Ordidge fears that adding cost to the practice of high-field imaging could make it more difficult for Europe to compete against research centers in the U.S., where similar prohibitions do not exist.

In fact, U.S. authorities appear to be moving in the opposite direction. Last July, the FDA announced that in most cases it is no longer necessary to obtain authorization for studies using MR scanners under 8T. The safety threshold had previously been set at 4T.

"Clearly, this matter is of grave concern for people who want to do high-field MR," Ordidge said. "The safety issue will be a thorn in the side of Europe. We don't want to be at a disadvantage, particularly as the Americans have extended their limits."

The main health concern is that exposure to high field strength magnets sometimes causes dizziness. While evidence shows that this can occur, the condition is uncommon, and there is no indication that it persists or poses a long-term health risk, Ordidge said.

For more information from the Diagnostic Imaging archives:

• Fast spin-echo imaging at 4.7T becomes feasible

• FDA loosens reins on investigational MR

• MR safety guidelines: facility design considerations

• New signs help control access to the MR environment