SAR Dosimetry, Pennes Bioheat Modeling, ISO 14971 Risk & FDA 510(k)/De Novo Pathways
IEC 60601-2-33: Head SAR $\le 3.2\,\text{W/kg}$; Local 10-g tissue $\le 10\,\text{W/kg}$.
Prevents focal RF burns near conductive leads and eye cataracts.
IEC 60601-2-37: Mechanical Index $\text{MI} \le 1.9$; $I_{\text{spta}} \le 720\,\text{mW/cm}^2$.
In unossified neonatal fontanelles, conservative $\text{TIS} \le 0.7$ avoids focal cavitation.
ANSI Z136.1 / IEC 60825: MPE $\le 0.2 - 0.4\,\text{W/cm}^2$.
Transducer skin contact temperature must remain $< 41^\circ\text{C}$ to prevent thermal injury.
Low risk devices (e.g., standard passive surface electrodes).
Exempt from premarket notification; requires GMP registration and quality system (QSR).
Moderate risk (diagnostic fNIRS, diagnostic ultrasound, clinical aEEG).
Demonstrates Substantial Equivalence (SE) to an existing predicate device within 90 days of review.
High risk / life-supporting (implantable DBS, intracortical BCI).
Requires prospective multi-center clinical trials proving safety and efficacy.
Mandates explicit pediatric subpopulation assessment (neonate, infant, child, adolescent).
Requires preclinical proof of skin safety on immature stratum corneum and long-term neurodevelopmental biocompatibility.
For HIE devices operating during 72-hr systemic cooling ($33.5^\circ\text{C}$):
Device must guarantee zero rewarming hot-spots ($< 0.5^\circ\text{C}$ local rise) to maintain neuroprotective hypothermic target temperatures.
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