Criteria for Significant Risk Investigations of Magnetic Resonance Diagnostic Devices
This guidance outlines the criteria for determining when investigations of Magnetic Resonance Diagnostic Devices (MRD) are considered significant risk, requiring FDA approval of an Investigation Device Exemption (IDE). It applies to class II devices under 21 CFR 892.1000, including Magnetic Resonance Imaging Systems and Magnetic Resonance Spectroscopic Systems.
Recommended Actions
- Assess planned operating conditions against the specified limits for magnetic field, SAR, gradient fields, and sound pressure
- If any operating condition exceeds the specified limits, prepare for IDE submission
- Implement appropriate safety controls and monitoring for all specified parameters
- Ensure compliance with IRB and informed consent requirements
- Contact FDA for clarification on local SAR criteria if needed
- Review complete risk assessment beyond just operating conditions
- Maintain documentation of operating conditions and safety measures
- Establish protocols for monitoring and maintaining operating conditions within specified limits
Key Considerations
Clinical testing
- Studies requiring IDE approval must comply with institutional review boards (21 CFR Part 56) and informed consent (21 CFR Part 50)
- After substantial equivalence determination, clinical studies conducted within approved indications are exempt from IDE requirements
Safety
- Main static magnetic field limits:
8 tesla for adults, children, and infants > 1 month
4 tesla for neonates (≤ 1 month)
- Specific Absorption Rate (SAR) limits:
- Whole body: > 4 W/kg averaged over 15 minutes
- Head: > 3.2 W/kg averaged over 10 minutes
- Gradient fields: Any rate of change causing severe discomfort or painful nerve stimulation
- Sound pressure limits:
- Peak unweighted level > 140 dB
- A-weighted RMS level > 99 dBA with hearing protection
Other considerations
- Operating conditions beyond these limits qualify as significant risk under 21 CFR 812.3(m)(4)
- Other aspects of the study may involve significant risks requiring IDE approval regardless of operating conditions
Relevant Guidances
- Testing and Labeling of Medical Devices for Magnetic Resonance (MR) Environment Safety and Compatibility
- Assessment of Radiofrequency-Induced Heating in Multi-Configuration Passive Medical Devices for MR Conditional Labeling
- Premarket Notification Requirements for Magnetic Resonance Diagnostic Devices
Related references and norms
- 21 CFR 892.1000: Magnetic Resonance Diagnostic Device
- 21 CFR Part 812: Investigational Device Exemptions
- 21 CFR Part 56: Institutional Review Boards
- 21 CFR Part 50: Protection of Human Subjects
Original guidance
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