Evaluation of Thermal Effects from Medical Devices on Human Tissue (DRAFT)
This guidance focuses on evaluating thermal effects of medical devices that produce tissue temperature changes (heating and/or cooling) as either an intended or unintended consequence of device use. This includes devices that: - Deliver radiofrequency, microwave, light, or other electromagnetic energy - Deliver ultrasound - Use electroporation - Produce temperature changes through contact - Have electrical components that can heat surrounding tissue
This is a draft guidance. Not for implementation.
Recommended Actions
- Determine appropriate testing methodology based on device characteristics and intended use
- Conduct verification testing of device parameters before thermal effects assessment
- Perform experimental assessment using appropriate model (phantom, ex vivo, in vivo)
- Document temperature-time history and dimensions of thermally affected tissue
- Validate any computational models used for evaluation
- Consider need for clinical testing if non-clinical results insufficient
- Develop comprehensive labeling with thermal effect dimensions and parameters
- Submit Pre-Submission to FDA for feedback on testing approach if needed
- Ensure testing covers full range of device specifications and use conditions
- Document scientific rationale for chosen testing methods and acceptance criteria
Key Considerations
Clinical testing
- Clinical data may be needed when non-clinical and animal studies are insufficient
- Studies should test full range of device parameters in intended population
- Must include safety measures and monitoring of target/non-target organs
- Results should document thermal injury and temperature-time history
Non-clinical testing
- Verification of device parameters through bench testing required
- Testing should cover full range of specifications with predefined acceptance criteria
- Must be done before assessment of tissue effects
- Deviations from acceptance criteria need scientific rationale
Labelling
- Include chart/graph showing dimensions of thermally affected tissue region
- Show relationship between power settings, activation duration and tissue types
- Document expected damage to facilitate safe use
Safety
- Assessment of tissue effects and thermal energy spread required
- Testing should evaluate minimum, average and worst-case temperature-time history
- Must allow tissue to return to baseline temperature
- Consider immediate and long-term tissue effects
Other considerations
- Phantom testing appropriate for minimal temperature changes (≤6°C)
- Ex vivo testing suitable for local temperature changes >43°C
- In vivo testing needed for prolonged or regional/systemic temperature changes
- Computational modeling can be used if properly validated
Relevant Guidances
- Electromagnetic Compatibility for Medical Devices and Accessories: Testing, Documentation, and Labeling Requirements
- Animal Testing for Medical Device Safety and Performance Evaluation
- Recommended Format and Content for Non-Clinical Bench Performance Testing in Medical Device Premarket Submissions
- Reporting of Computational Modeling and Simulation Studies in Medical Device Submissions
- Assessing the Credibility of Computational Modeling and Simulation in Medical Device Submissions
Related references and norms
- IEC 60601-2-33 Ed.4.0: Medical electrical equipment - Part 2-33: Particular requirements for the basic safety and essential performance of magnetic resonance equipment for medical diagnosis
Original guidance
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