The Food and Drug Administration (FDA or the Agency), the US regulating authority in the sphere of medical devices and other healthcare products, has published guidance describing the most important aspects related to testing and labeling of medical devices for safety in the magnetic resonance (MR) environment. The present document constitutes a final version of the guidance initially published by the authority earlier in August 2019. It also replaces the guidance dedicated to the same matters issued by the FDA in December 2014.
Due to the legal nature of the document, it does not introduce any rules or requirements the parties involved shall follow but provides additional clarifications and recommendations to be considered. Additionally, the Agency mentions that an alternative approach could be applied, provided such an approach complies with the applicable regulatory requirements and has been approved by the authority in advance.
Regulatory Background
The present FDA guidance describes the testing to be performed in order to assess the safety and compatibility of medical devices in the MR environment. Additionally, the document clarifies the requirements for Magnetic Resonance Imaging (MRI) Safety Information to be included in the labeling of a medical device. The document also contains references to the voluntary consensus standards recognized by the FDA to be used by the medical device manufacturers for demonstrating compliance with the applicable requirements.
The scope of the guidance covers any and all medical devices that could be used in the MR environment (e.g., implanted ones). With regard to labeling, the document refers to the applicable standard ASTM F2503 Standard Practice for Marking Medical Devices and Other Items for Safety in the Magnetic Resonance Environment. At the same time, magnetic resonance systems and accessories thereto fall outside the scope of the present guidance.
The recommendations provided in the guidance could be applied in the context of such submissions as:
- Premarket approval (PMA) application,
- Humanitarian device exemption (HDE) application,
- Premarket notification (510(k)) submission,
- Investigational device exemption (IDE) applications, and
- De Novo requests to be submitted in case of medical devices based on novel technologies.
First, the FDA provides the definitions of the most important terms used in the context of the guidance, namely:
- Active medical device – medical device relying for its functioning on a source of electrical energy or any source of power other than that directly generated by the human body or gravity.
- Controlled Access Area – area around the MR system, to which access is controlled to prevent harm from the Static magnetic field.
- Magnetic Resonance (MR) environment – the three-dimensional volume of space surrounding the MR magnet that contains both the Faraday shielded volume and the 0.50 mT field contour (5 gauss (G) line). This volume is the region in which a medical device might pose a hazard from exposure to the electromagnetic fields produced by the MR equipment and accessories.
- Magnetic Resonance (MR) System – an ensemble of MR equipment, accessories including means for display, control, energy supplies, and the controlled access area, where provided.
Apart from the ones listed above, the document also provides the definitions of such terms as “MR Conditional,” “MR Safe,” “MR Unsafe,” “Passive implant,” “Passive medical device,” and “Active implantable medical device (AIMD).”
As mentioned, the medical device manufacturers may refer to the applicable FDA-recognized voluntary consensus standards in order to demonstrate compliance with the applicable regulatory requirements in terms of safety within the MR environment. The present guidance contains a list of such standards.
Addressing Hazards and Risk Management
The FDA acknowledges the specific nature of risks associated with the use of medical devices in the magnetic resonance environment. These risks should be a part of risk management for all medical devices to which this applies. This includes such elements as special testing to be carried out in order to evaluate the actual performance of a medical device in the magnetic resonance environment, as well as scientific rationale. The document describes in detail the main hazard associated with the use of a medical device in the MR environment and also outlines standardized test methods to be applied. The guidance also addresses the risks associated with the MR systems.
According to the document, such risks would vary depending on such factors as:
- The characteristics of the static magnetic field,
- Gradient magnetic fields,
- Radiofrequency coils.
The abovementioned characteristics would impact the risk profile of the MR system, so their variations should be considered by the manufacturer when assessing the safety and performance of the product before placing it on the market.
The guidance also highlights certain thresholds to be taken into account when assessing the safety-related aspects. In any case, the medical device manufacturer shall demonstrate that the product intended to be marketed and used in the US is safe and does not expose patients to additional risks. The appropriate testing constitutes an important part of the assessment process – the authority states that in certain cases, medical devices that belong to the same type could have different risk profiles due to differences in design, so testing conducted in accordance with the applicable methodologies constitutes one of the key points of assessment. The Agency also encourages medical device manufacturers to discuss testing plans before commencing the process. In such cases, the Q-Submission framework could be applied.
Additional Aspects
The document describes in detail the most important safety-related aspects medical device manufacturers shall take into consideration in the context of the impact caused by magnetic resonance. This includes potential dislodgement of a medical device due to the impact of the spatial gradient of the static magnetic field. Such risks should be considered for any and all medical devices intended to be used in the magnetic resonance environment. If the device could exist in various modifications, the worst-case scenarios are the ones requiring the most attention to be paid during testing and further analysis.
The Agency additionally emphasizes the risks associated with implanted medical devices, which are vulnerable to the impact caused by the magnetic field. According to the document, they are less exposed to the risks associated with displacement of the device (as with devices fastened to the patient). However, the magnetic resonance environment could intervene in their normal operations.
In summary, the present FDA guidance covers the most important aspects related to the use of medical devices in the magnetic resonance environment. The document describes the main risks and highlights key factors to be considered in the course of testing and analysis.
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