Many filtering face piece (FFP-3) respiratory masks, commonly used in MRI settings during the COVID-19 pandemic, can be unsafe for MRIs, according to a new study accepted for publication in Clinical Radiology.[1] 

The safety risks stem from the presence of ferromagnetic components, which were found in five out of eight commercially available masks tested. Risks include artifacts on the MRI, deflection or displacement of the mask, risk of projectile effects, and radiofrequency-induced heating that could potentially cause burns. The masks deemed MRI-unsafe caused observable grid distortion of up to five centimeters. 

“This study has demonstrated the importance of assessing respiratory FFP3 masks for use in and around MRI machines,” wrote first author Bethany Keenan, MD, and co-authors. 

In addition to better understanding safety risks and grid distortion, the study also aimed to determine which masks can be considered safe for use in an MRI setting, as it isn’t obvious through outward observation alone. While some metallic components—such as metal nose strips—are immediately visible, others—such as silver or copper antimicrobial coatings—are difficult to observe. Additionally, the study notes that not all face masks are labeled appropriately. 

“It is therefore important to not assume that the mask is safe prior to an MRI examination, and to conduct a safety evaluation to determine which components are made of ferromagnetic metals (such as steel) and which are non-ferromagnetic metal (such as aluminium),” the authors wrote.