Implants

The MHRA defines implanted medical devices in two main categories: Active and Non-active. Active implants contain metallic components and require an energy source, whereas non-active implants contain metallic components and do not require an energy source in order to function, these are sometimes referred to as “passive implants”.

Implantable devices can contain electrical and metallic components which are affected by the static magnetic field, time varying magnetic field gradients and radio frequency electromagnetic fields in MRI. Some implants are not compatible with MRI and are therefore contraindicated by the implant manufacturer, or they may cause artefacts that can affect image quality.  Many active and non-active implants are MR Safe or MR Conditional and as part of carrying out good MR safety checks this information should be obtained before the patient attends for their scan. Specific implant information should be documented in the patient’s permanent records, and some patients are given documentation and information about their implant by their surgeon.

The MHRA recommends that the hospital should develop a policy for the identification, documentation, imaging and provision of any necessary aftercare for patients with implantable medical devices undergoing an MR examination (section 4.11 Safety Guidelines for Magnetic Resonance Imaging Equipment  in Clinical Use, 2015). 

‘Off label’ scanning of implants

‘Off label’ scanning is a term that has only been recently used in the MRI community. This process is followed when it has not been possible to check implant or device safety for one or more reasons, but where MRI has been indicated as clinically valuable for the patient. MHRA guidance – section 4.11.4 ‘Scanning patients with implants where MRI may be contraindicated’

Active Implants

Functionality of these implants is dependent upon an energy source such as electrical, mechanical or pneumatic power.  Examples of active implants include pacemakers and defibrillators, cochlear implants and auditory brainstem implants, neurostimulators and drug infusion pumps.

Relevant links and articles:

Pacemakers:

Leadless cardiac pacemakers: used for implantation in adults with bradyarrhythmias. This involves inserting a device into the heart that helps it beat at a normal rate.

Pacemaker Manufacturers:

Neurostimulators:

Deep Brain Stimulators

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Non-active Implants

These implants do not require a power source in order to function. Examples of non-active implants include joint replacements, heart valves, aneurysm clips, programmable shunts, breast implants and intravascular stents.

Relevant links and articles

Programmable Shunts

Heart Valves

Cochlear Implants

BAMRR Article ‘Scanning Cochlear Implants & Auditory Brainstem Implants in MRI’ – Cath MillsDownload