MRI Safety: Contraindications, Precautions & Who Should Avoid Scans

MRI uses a powerful static magnetic field (1.5–3T typical), gradient fields, and RF pulses. Safety screening is mandatory.

Absolute Contraindications (Unless Device Is MRI-Conditional & Protocols Followed)

• Cardiac pacemakers / ICDs (older models). Modern MRI-conditional devices require specific programming, monitoring, and SAR limits.
• Cochlear implants (most). Some newer are conditional.
• Neurostimulators (DBS, VNS, SCS) — mostly conditional now with strict protocols.
• Ferromagnetic intracranial aneurysm clips (pre-1995). Modern clips (titanium, Phynox) are safe.
• Metallic foreign bodies in orbits (risk of movement/heating). X-ray orbits if history of metalwork.
• Implanted infusion pumps (some).

Relative Contraindications / Precautions

• Pregnancy: Generally safe (no ionizing radiation). Avoid 1st trimester unless urgent. Gadolinium contrast: Category C — avoid unless essential.
• Severe claustrophobia: Options: open MRI (lower field), wide-bore, sedation (oral/IV), anxiolytics, prone/feet-first, mirror/prism, music/video.
• Renal impairment (eGFR <30): Gadolinium-based contrast agents (GBCA) risk NSF. Use macrocyclic agents (lower risk) or avoid contrast.
• Allergy to GBCA: Rare. Premedicate (steroid/antihistamine) or use alternative imaging.
• Obesity: Bore size (60–70 cm) and table weight limit (250–350 lbs). Open/upright MRI alternatives.
• Inability to lie still: Pediatrics, dementia, severe pain → sedation/anesthesia support.

Screening Process

1. Written questionnaire (implants, surgeries, metalwork, pregnancy).
2. Verbal review by technologist.
3. Ferromagnetic detector (wand/gate) at zone III/IV entry.
4. Device cards / implant IDs verified.

Never enter Zone IV (scan room) without clearance. "MRI safe" ≠ "MRI conditional."