MRI Safety Screening Form Explained

MRI is safe and does not involve any ionising radiation (x-rays). 

However, because it uses a large magnet to work, MRI scans are not suitable for everybody.

We ask these safety questions to determine if you can take part and sometimes, we would need more information before you take part in the research MRI scan.

You can see the questions that we ask, and the reason we ask them in this document, or by clicking on the question links below.

MR scanners have inbuilt safety systems to prevent excessive heating during a scan, and different manufacturers have different ways of doing this. The systems we use rely on models that require height, weight, and biological sex and therefore it’s important we know this information.

Many older pacemakers are unsafe to be scanned (and even some of the newer ones). The magnetic field can permanently damage some of their components such as reed switches.

Sometimes when a person has had a pacemaker removed, it’s not possible to remove the pacing wires. This can be for a variety of reasons but there is a risk that these wires can heat up during a MR scan. If you have had a pacemaker in the past, we will confirm that the pacing wires have been removed before your MR scan.

These are all devices that can be implanted to make ensure that blood flows through the heart correctly. Most medical implants have had MR safety testing and the manufacturers provide information on how to safely scan these implants.

Some surgeries to the eyes, ears or brain can involve the use of implants e.g. lens replacements, aneurysm clips, shunts, scleral buckles, inner ear implants. The eyes, ears and brain are very sensitive structures, so we need to know if any implants are present.

Operations to the neck or spine can involve implants with complex shapes e.g. cages and pin & plate systems with multiple components. Many of the implants are ok to scan but we first need to check what is present, and sometimes we need to contact implant manufacturers for safety guidance.

Some implants, such as the ones mentioned in this question, are especially important to know about. This can be because they are mechanical or electronic, are on sensitive structures, or vary in their location in the body.

These are mostly orthopaedic implants use to fix broken bones. They can have unpredictable and complex shapes which is why we sometimes need to do extra checks to confirm that it is safe to scan you. 

The 6-week timeframe can be important for certain operations.

 Sometimes with endoscopy, particularly when biopsies are taken, your doctor can use endoscopy clips. These clips will naturally fall off and leave the body, but this can take a few weeks. After 6 weeks we would not expect any clips to remain.

 Generally, surgeries that do not involve certain implants are ok to scan within 6-weeks. However, we also take into consideration whether you would be comfortable having an MR scan while you are recovering.

Most people don’t know exactly what was done when they have an operation. It is not unusual for implants, such as surgical clips, to be used without you being aware of it. The radiographers are experts in knowing which surgeries are safe and which surgeries require more information to confirm safety.

It is very important to let us know about any injuries involving metal, especially to the eyes, before you have an MR scan. Unlike implants, which are attached to structures and made of known materials, metal introduced from an injury could be attracted to MR scanner. You may still be able to be scanned if you have had a metal injury, but we will carefully assess this first. 

If you have had a serious accident or injury, you may not remember what hospital care you had after the injury. We want to make sure you do not have any metal in your body, this could either be from the injury itself or operations you had afterwards.

We ask this question to check if you’ll be ok during your scan. If you have a history of the above, you can still be scanned but we will ask you about any previous incidents and how well controlled your epilepsy or diabetes is at this moment in time.

Body piercings vary considerably in terms of their composition. Some metal items can be attracted to the strong magnetic field and conductive materials could heat up during the scan. We will ask you to remove any body piercings before your scan, alternatively any plastic materials are normally fine to leave in.

Eye shadow and mascara must be avoided, since some types contain materials that can interact with the magnetic field e.g. iron oxide is often used in mascara to give it a dark colour. If you wish to wear eye makeup to your scan, we can provide makeup removal wipes, but you are advised to bring your own makeup to reapply.

Coloured contact lenses, the type that change the colour of your eye, can contain metal which can show up on the scan. Normal contact lenses, that have a blue tint, are fine to wear during your scan.

These items are particularly sensitive to the strong magnetic fields used for MR. If you have a drug pump or a glucose monitor it is important that we check with your doctor before removing them.

While fillings are always ok for an MR scan, other dental materials can sometimes be attracted to the magnetic field. If we are concerned about a dental material, we may ask you to contact your dentist to find out what it is made of.

Medicated skin patches, with or without a foil backing, can heat during an MR scan and deliver a large dose of the drug they contain. If you have one of these we will check where it is on your body and may ask you to remove it. It is important to note that, for anything that is prescribed, we need to check with your doctor first.

On very, very, rare occasions tattoos can heat up during a MR scan. The mechanism for why this can happen is poorly understood though it seems that tattoos with metallic pigments are more likely to heat. You should let us know if you have tattoo(s), for most of our scans we will simply warn you to alert us if you feel any heating during your MR.