The reasoning: three fields, three hazards
| Field | Hazard | Mitigation |
|---|---|---|
| Static B₀ (1.5–3 T; always on) | projectile effect (ferromagnetic objects), torque/displacement of implants | ACR four‑zone access control, screening, ferromagnetic detectors, MR‑conditional equipment |
| RF field | heating, burns (specific absorption rate, SAR), conductive loops, leads | SAR limits, padding, no skin‑to‑skin loops, remove ECG leads not designed for MR |
| Gradient fields | acoustic noise (> 100 dB), peripheral nerve stimulation | hearing protection for all, dB/dt limits |
| Cryogens (liquid helium) | quench → asphyxia, cold burns | quench pipe, oxygen monitor |