In their testing of eight commercially available filtering face piece (FFP3) respirators commonly utilized during the COVID-19 pandemic, researchers deemed that five of the face masks that contained ferromagnetic materials were unsafe to use in and around magnetic resonance imaging (MRI) devices.
New research suggests that face masks using ferromagnetic components should not be utilized during magnetic resonance imaging (MRI) exams.
In a study published in Clinical Radiology, researchers at the Cardiff University Brain Research Imaging Centre tested eight filtering face piece (FFP3) respirators to determine possible impacts on local heating, grid distortion and imaging artifacts during MRI exams.
Utilizing an MRI-compatible head and neck phantom and a 3T MRI system (Siemens Magnetom Prisma), the study authors ran three MRI sequences to test the FFP3 masks. These sequences included three-dimensional (3D) susceptibility-weighted imaging, two-dimensional (2D) echo-plantar imaging (EPI) and 3D magnetization-prepared rapid gradient echo (MPRAGE) imaging, according to the study.
The study authors found that the five masks containing ferromagnetic materials distorted the internal lattice grid structure of the anterior portion of the phantom head model. The gradient echo images revealed “substantial image (artifacts)” for the masks with ferromagnetic components, according to lead author Bethany Keenan, MD, who is affiliated with the Cardiff University Brain Research Imaging Centre and the Cardiff School of Engineering at Cardiff University in the United Kingdom, and colleagues.
“There is limited information available regarding the implication of wearing a facemask on other types of MRI sequences and, as such, care must be taken when conducting any study where these types of masks are used,” wrote Keenan and colleagues. “It is important to note that the MRI sequences used within the present study are typical of those used clinically. Therefore, the duration of exposure and its possible effect were not assessed, but an increased acquisition time may worsen the results (i.e. cause induced local heating).”
The face masks in the study included the Handanhy 9330 and 9632 masks, the 3M Aura 9320+ and 9330+ masks, the GVS Segre F31000 mask, the Easimask FSM 18 mask and masks from Valmy Spireor and Cardinal Health. Keenan and colleagues said the Easimask FSM 18 and Handanhy 9632 masks were “MRI safe” as they did not have metal components. They added that the GVS Segre F31000 mask was “MRI conditional” due to a potential risk of local heating when using imaging with higher specific absorption rate (SAR) sequences.
In addition to MRI artifacts and radiofrequency-induced heating, metallic components in face masks may cause displacement of the mask, reducing its effectiveness, according to the study authors.
In terms of study limitations, the authors noted it is not possible to assess the large numbers of FFP2 and FFP3 masks that are currently available. However, they did point out that the masks in their study included duckbill, cone-shaped, bifold and trifold designs that were utilized during the COVID-19 pandemic by the National Health Service (NHS) Wales and NHS England.