Personal protective equipment (PPE) such as N95 respirators are "MR unsafe" and pose a risk to technologists, wrote a team led by Dr. O.M. Murray of Mater Private Hospital in Dublin, Ireland. (In Europe, comparable respirators to the N95 are called FFP2 or FFP3.)
"Staff accompanying patients with suspected or confirmed COVID-19 are likely to be wearing respirators when they arrive at the MRI room," the group wrote. "MRI staff may also be wearing a respirator as part of their personal protective equipment when dealing with these patients. These staff members may not be aware that respirators and facemasks do not have MRI safety documentation and as such require testing."
Murray and colleagues tested a variety of respirators for magnetic attraction outside the MRI control area using a handheld magnet (<1,000 Gauss); they also placed the masks on a human head phantom that was positioned on the MRI table (Clinical Radiology, June 2020, Volume 75:6, pp. 405-407).
The respirators tested included the following:
- 3M Aura respirator FFP3 1863
- Kolmi respirators, FFP2 and FFP3
- Halyard Technology FFP2 respirator
- Dahlhausen surgical facemask
The 3M and Kolmi respirators had components that reacted to the magnet, while the Halyard did not, the group found. The surgical mask showed no signs of magnetism; the aluminum strip that fits over the nasal bridge had negligible effect on imaging.
Technologists should test respirators and face masks before using them in the MRI suite, the group concluded.
"This study has shown that several commercially available respirators contain ferromagnetic components, and are thus regarded as 'MRI unsafe,'" it wrote. "As such, the use of these respirators by staff in the MRI room is contraindicated, both for MRI safety reasons and because they offer suboptimal protection against COVID-19 due to torque, causing a break in the seal at mask-user interface."
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