MR-Safety Labelling
| Label | Meaning |
|---|---|
| MR Safe (green square) | Poses no known hazard in any MR environment — non-conducting, non-metallic, non-magnetic |
| MR Conditional (yellow triangle) | Safe under specified conditions (field strength, gradient, RF limits) — most anaesthetic equipment used in-room is this |
| MR Unsafe (red circle) | Ferromagnetic / hazardous — must never enter the MR environment |
Common Mistakes
Taking unchecked / ferromagnetic equipment (steel O₂ cylinder, laryngoscope, standard pump) into Zone IV → projectile.
Looped/coiled cables against skin → RF burns.
Trying to resuscitate inside the magnet room instead of evacuating the patient first.
Lowering the standard of monitoring/assistance because it is "just a scan" — remote-location anaesthesia demands full theatre standards.
Viva-Ready Pearls
The static field is always on — you cannot switch the magnet off for an emergency (only a quench).
Four ACR zones: I public → II screening → III control room → IV magnet.
The projectile effect is the signature lethal hazard; ECG is distorted by the magnetohydrodynamic effect.
Golden rule: in an emergency, get the patient out of Zone IV and resuscitate outside the field.
Gadolinium → NSF in severe renal impairment; scan noise → hearing protection.
References
- AAGBI — Safety guideline: Anaesthesia & sedation in remote locations / provision of anaesthetic services in the MRI unit.
- American College of Radiology (ACR) — Manual on MR Safety (safety zones & MR Safe/Conditional/Unsafe labelling).
- Miller's Anesthesia — Anesthesia at Remote Locations; Anesthesia for MRI.
- Morgan & Mikhail's Clinical Anesthesiology — Non-operating-room anaesthesia.