Contraindications to MRI

Implanted Devices

1. Cerebral aneurysm clips – absolute contraindication
2. Cardiac defibrillators and pacemakers – absolute contraindication
3. Pacing wires left in place after bypass surgery
4. Mechanical heart valves – though some are safe
5. All electronic implants eg bladder, vagal nerve or neurostimulators
6. Metal implants during eye or ear surgery
7. IVC filters – though some are safe
8.  Implantable drug infusion pumps.
9. Programmable hydrocephalus shunts. (If these patients are to undergo an MRI examination, then a programmer and a trained clinician should be available to verify the correct setting and to reprogram the device (if required), immediately following the MR procedure. Advice must be given to the patient on how to recognise over- and under-drainage and who to contact should these conditions develop).

Operating surgeons and treating physicians to provide documents evidence of the devices and either MR SAFE or MR CONDITIONAL status.

Transdermal Patches

1. Transdermal medicinal patches containing metal and those that may be affected by heat should be removed and replaced after scanning if this can be done without affecting patient treatment, e.g. Transdermal patches containing Fentanyl.

Foreign Bodies

1. Shrapnel/pellets
2. Previous metal in eyes – will require orbital xray to confirm no longer present unless 100% metal removed in hospital
3. Surgical clips if within 8 weeks of surgery

Pregnancy

1. MRI not advised during first trimester as precautionary measure though this can be overridden in case of urgent clinical need
2. Recent concerns regarding hearing damage to foetus at any stage of pregnancy – important to inform MR staff

Renal Failure

1. Nephrogenic systemic fibrosis is a chronic progressive sclerosis of skin, deeper tissues and internal organs that is associated with gadolinium based contrast agents used for MRI
2. NSF only reported in patients with renal impairment, typically on dialysis or with eGFR <15ml/min but best to avoid gadolinium if eGFR <30ml/min. No specific treatment exists

Other

1. Obesity – must inform MR staff if patient weighs >250kg
2. Claustrophobia – for some this may be severe enough to require sedation
3. Tattoos may contain iron oxide or other ferromagnetic substances that are conductive.  During scanning, patients should be asked to report any discomfort immediately/

The Following Must Be Removed

1. Insulin pumps
2. Artificial eyes
3. Contact lenses
4. Rings and earrings, tongue studs etc
5. Medication patches eg GTN, nicotine and analgesic patches
6. Eye shadow
7. Back braces
8. Artificial limbs
9. Body piercing
10. Patient clothing (It is recommended that patients change into appropriate clothing provided by the MR unit to ensure safety and to prevent artefact production. The material and design of such clothing should not contain metallic fibres, labels, pockets, buttons or fasteners, nor should it inhibit heat loss).

The Following Are Safe But Let MR Staff Know Anyway

1. Most orthopaedic pins, screws and wires
2. Joint prostheses – though may cause artefact if the joint replaced is the joint being scanned.  The presence of bilateral hip implants appears to increase the risk of discomfort and burns.
3. Sternal wires
4. Lens implants
5. Intra-uterine devices. Testing has indicated that these objects are safe for patients using MR systems operating at 1.5 T or less.
6. Hernia mesh
7. Dental work – though may cause artefact especially braces

Labelling

1. Appropriate labelling as
   1. MR CONDITIONAL
   2. MR UNSAFE
   3. MR UNLABELLED
   4. MR SAFE

Links

• MHRA Safety Guidelines for MRI Equipment
• MRI Safety
• MRI Safety Leaflet – Patients
• MRI Safety Leaflet – Referrers

Content Updated by Dr Sameer Kalgaonkar