With a view to the absolute safety of patients, medical device manufacturers must be aware of the potential risks of magnetic resonance imaging (MRI). This involves, for example, the functionality of implants, compatibility with other medical devices used in this environment, and the safety of patients wearing medical implants. This means a lot of responsibility for the manufacturers, which can be addressed with MRI safety tests, among other things.
Originally developed in the late 1970s after decades of research and experimentation, MRI technology now plays an important role in healthcare, be it in the diagnosis, treatment, or management of various types of cancers and a range of other medical conditions. MRI scans give healthcare professionals the ability to identify potentially serious conditions at the very earliest stages, helping to ensure successful treatment outcomes. And MRI scans are noninvasive and generally painless for the patient and eliminate the risk of exposure to radiation such as that found in x-rays and CT scans.
At the same time, the use of MRI technologies can present potential hazards to patients with implantable medical devices, as well as to personnel in the MRI scanner environment. These hazards can compromise the operation of these potentially life-saving devices and place the health and safety of patients at risk. If medical devices or implants are located near an MRI system, there are risks associated with that proximity. For example, the electromagnetic fields of MRI can interfere with the function of pacemakers or middle ear implants due to the magnetic field generated. Nonactive medical implants such as artificial joints made of metal can interact with the MRI due to the electromagnetic radiation. This interaction may result in injury or health risks.
Accordingly, implantable medical devices must be thoroughly evaluated and tested to ascertain the possible impact of such hazards and the degree of potential risk in the MRI environment. Medical device manufacturers have a duty to reliably test their products for risks associated with use in an MRI environment. During so-called MRI safety testing, OEMs receive recommendations for the safety and usability of their products in connection with MRI diagnostics and, in addition, essential information for their labeling even before market entry.
Implantable Medical Devices in the Regulatory Environment
Regulators in major jurisdictions around the world are actively working to address the potential risks to patients with implantable medical devices in the MRI environment. For example, the U.S. Food and Drug Administration (FDA) requires that device manufacturers submit to the agency an application for premarket review for any new or substantially modified medical device they wish to place on the market. To address the specific safety challenges associated with implantable medical devices in the MR environment, the agency issued in 2021 an updated version of its guidance document on the “Testing and Labelling of Medical Devices for Safety in the Magnetic Resonance (MR) Environment” (Docket Number FDA-2019-D-2837). And in Europe, the EU’s Medical Device Regulation (EU 2017/745, also known as the MDR) sets forth rules applicable to all medical devices sold or marketed in EU member states.
Meeting regulatory requirements applicable to active and nonactive implantable medical devices generally requires that device manufacturers demonstrate compliance with the specifications of one or more of the industry-accepted consensus standards. Currently, these are ASTM F 2052, 2213, 2182, 2119, 2503 as well as ISO/TS 10974. Each of these standards is recognized by the U.S. FDA as a consensus standard for use with medical device testing and labeling. While none of the above standards have yet to be published as harmonized standards under the EU’s MDR, these standards do represent current state-of-the-art practices and should be considered in assessing an implantable device for compliance with the MDR requirements.
Labeling for MR safety
The end goal of any safety testing conducted on implantable medical devices is to determine the safety of that device in an MR environment. A safety framework is provided by the widely accepted standard ASTM F2503, “Standard Practice for Marking Medical Devices and Other Items for Safety in the Magnetic Resonance Environment.” It is applicable to implantable devices sold or marketed in both the United States and the EU. Under ASTM F2503, implantable devices are categorized in one of the following three categories:
MR Safe. This can be applied without testing to any implantable device that poses no known hazards in any MRI environment, including those that do not include any magnetic, conductive, or metallic materials.
MR Unsafe. This is the default category initially applied to all active implantable medical devices before testing. These devices include magnetic, conductive or metallic materials, and they have not been proven to be safe under any condition, as well as those known to pose hazards in MRI environments.
MR Conditional. This is applied to devices that include magnetic, conductive, or metallic materials. These devices have been tested and verified to pose no known hazards in a specified MRI environment and are accompanied by labeling that specifies the conditions of use.
At a minimum, nonactive (passive) implantable medical devices categorized as MR Conditional under ASTM F2503 have been tested for magnetically induced displacement force (ASTM 2052), magnetically induced displacement torque (ASTM F2213), and radio frequency induced heating (ASTM F2182). Additional testing may be required, depending on the unique characteristics of the implantable device.
Reliable Partners for MRI Testing
To fully comply with applicable standards for MRI testing, manufacturers should rely on Notified Bodies knowledgeable about the latest regulatory standards. TÜV SÜD, for example, is an EU Notified Body for the review and approval of medical devices, including implantable medical devices. The globally active service provider based in Munich, Germany, has also been accredited by the IMDRF’s Medical Device Single Audit Program (MDSAP), which provides a path for demonstrating compliance with key medical device requirements in the United States, Canada, Japan, Brazil, and Australia.
To conduct reliable testing, TÜV SÜD operates a new medical device testing facility in New Brighton, MN. The facility is ISO/IEC 17025:2017 accredited by the American Association for Laboratory Accreditation (A2LA) and can test MRI safety according to ASTM F2052, ASTM F2213, ASTM F2182, ASTM F2119, and ASTM F2503.
To support efficient product development, TÜV SÜD also engages with many device manufacturers in the early stages of product design and development. This enables the experts to test the prototype of the implantable devices to verify whether or not a product is on the path to regulatory approval.
TÜV SÜD has recently published a white paper on ensuring the safety of implantable medical devices in a magnetic resonance (MR) environment. It can be downloaded here .