MRI Safety with Metal on the Head
MRI is contraindicated for patients with stainless steel or non-titanium metal implants on the head due to significant safety risks including potential movement, displacement, and injury. 1, 2
Safety Screening for Metal Objects
- All patients must undergo thorough screening for ferromagnetic materials before entering the MRI suite to prevent potentially fatal accidents 2, 3
- Patients with metal on the head must be evaluated according to MRI safety classification (MR Safe, MR Conditional, or MR Unsafe) 2, 3
- The specific type, location, and material of any implant must be verified before scheduling an MRI examination 1
- Implants are categorized as:
Types of Metal and MRI Compatibility
- Ferromagnetic metals (like stainless steel) pose the highest risk due to potential movement in the magnetic field 4
- Titanium implants are generally considered MR safe and do not pose significant risks 5, 4
- Pure gold implants tend to move less in MRI than other materials 5
- Patients with stainless-steel implants cannot undergo MRI due to the powerful magnets in the machine 1
Risks Associated with Metal in MRI
- Movement or displacement of metal objects that could cause tissue damage 6, 4
- Significant image artifacts including signal loss, geometric distortion, and bright pile-up artifacts 7
- Potential thermal burns from metal objects that may heat during the MRI procedure 3
- Failure of fat suppression and other MRI mechanisms due to large resonant frequency changes 7
Alternative Imaging Options
- CT scanning is a safe alternative for patients with metal on the head 8
- CT is actually preferred over MRI for patients with suspected metallic foreign bodies 8
- Modern CT scanners include specialized protocols for reducing metal artifacts 8
Required Documentation and Verification
- The patient's implant pass must be requested and checked with the implant/device manufacturer to determine safety level 1
- All screening findings must be documented in the patient's medical record 2
- For "MRI conditional" implants, all specific conditions necessary for safe MRI examination must be verified 1
Practical Considerations
- Even MR-compatible metal can lead to artifacts that may complicate image interpretation 1, 7
- Metal implants can cause significant signal voids and geometric distortions in MRI images 1, 9
- All personal metallic items (jewelry, watches, clothing with metal components) must be removed before entering the MRI suite 3
- Patients should be provided with cotton clothing free of metal components 3
MRI safety with metal on the head requires strict adherence to safety protocols. When in doubt about the MRI compatibility of a metal implant, CT imaging should be considered as a safer alternative 8, 6.