Medical Resonance Imaging (MRI)

The Medical Resonance Imaging (MRI) team at PCH is made up of specialised paediatric MRI radiographers. We perform MRIs on children from neonates to 16 years old. Our vast paediatric skills and knowledge enable us to cater studies for different age groups and abilities, resulting in a high success rate of diagnostic MRIs performed. We are passionate about creating a calm and non-threatening environment and endeavour to make the MRI experience as amiable as possible, as we understand that it is a new and different experience for a lot of our patients.

The MRI department at PCH has been designed to be very colourful to provide a distraction for our patients and help them relax. We have two scanners at PCH, one in our main Diagnostic Imaging Department, primarily used for outpatients, and a second located in theatre for patients who need anaesthetic, intraoperative MRIs and for inpatients. MRIs are used in conjunction with other imaging modalities such as X-ray, CT and ultrasound to gain additional information to aid in diagnosis.

Our MRI machine is a big tunnel-like magnet, 3 Teslas, along with this strong magnetic field there is the introduction of radiofrequency pulses. The introduction of certain pulses at different times works by aligning the molecules in the body, which once detected by an antenna (the device placed over or around the region we are scanning) and then processed by the computer, results in a generation of a cross sectional 2D image. We do different types of sequences to look at different anatomy.

Your child will be required to lie on a table, sometimes on their back, sometimes on their stomach, and the table goes into the tunnel. The body area we are imaging is in the middle of the tunnel, so sometimes your head will be out one of the ends of the tunnel. If your child is not having an anaesthetic, a guardian can stay with them.

The MRI machine is very noisy when it takes the pictures. Both patient and accompanying adult are provided with hearing protection, either headphones, stick on ear muffs or ear plugs.

An MRI can be as quick as 15 mins or as long as an hour. The length of your imaging procedure will depend on what body part we are imaging, if we need to give contrast and if your child is staying still.

You can help your child prepare for an MRI scan by practicing laying still for a couple of minutes at a time at home before their appointment and talking to them about the loud noises the machine will make.

When you arrive at the MRI department, an office clerk will meet you and start the process of filling out the safety checklists and choosing a movie (if applicable, as for some regions it is not possible). If Emla is required this is applied to maximise the time it is on for. The MRI radiographer will then greet you, go through the safety checklist for the child and accompanying adult (if required). The radiographer will briefly explain the process of the scan, the requirement of laying still and the noisy scanner. Please have dressed your child in clothing free from metal zips, buttons or studs, however sometimes it is required to get the patient changed into hospital pyjamas.

Once everyone is deemed safe to go into the MRI scan room, the radiographer will explain the process and equipment a bit more. A device may be placed around the area to be imaged; this could be helmet-like over the head. The radiographer may use straps, sponges and sandbags to help immobilise and aid your child in staying still. Most sequences last for a couple of minutes, this is when there will be the loud knocking noise. Usually there are up to seven sequences to get a complete scan, there will be a short break in between sequences when the radiographer will talk to your child and check they are ok. We discourage parents talking to the child during this time as the child is tempted to move to see you and this distracts them from listening to instruction given by the radiographer. The radiographer can always see the child in the MRI scanner.

For children who are requiring anaesthetic there are further checks done upon arrival with the admitting nurse, anaesthetist and theatre staff. Parents are not allowed to accompanying their child into the MRI for their scan under anaesthetic. All children undergoing an anaesthetic are required to fast, please follow fasting instructions on your appointment letter.

For babies aged up to 12 weeks, we will attempt to scan the baby following a feed. This is when baby is usually most settled. We allow extra time to settle the baby and encourage dummies and parents in the room to help. We have a special bean bag we use to wrap them in so they feel snug and secure and this helps immobilise them.

Some children are required to fast for various scans, usually abdominal. They may also be required to drink some contrast to help visualise the bowel. This information will be on your appointment letter if relevant. For many abdominal scans the child will be required to hold their breath, this is also necessary for cardiac scans. These instructions will be conveyed to your child upon arrival and during the scan.

Usually we can predict when we will require the use of the contrast medium, Gadolinium. Your appointment letter will advise this and you have the opportunity to arrive early for the application of a topical anaesthetic, Emla. This usually takes up to 40 minutes to work; it is very effective in numbing the area for injection.

There is a very small risk of allergic reaction to Gadolinium; some people do experience a brief bout of nausea or hives. If your child has known kidney problems or disease it is best to check kidney function prior to the administration of Gadolinium, as there is a rare but serious complication of nephrogenic systemic fibrosis following Gadolinium injections.

As MRI uses magnets and radiofrequency pulses, there is no radiation risk; however the biggest safety risk is an introduction of metal objects and electronic devices into the MRI environment. Metal objects have the potential to become a dangerous projectile due to the strong magnetic field. Metal objects also present the risk of heating up and causing burns. Electronic devices run the risk of the magnetic field interfering with the workings of the device, eg pacemaker, pumps or hearing devices, resulting in malfunction or injury to the person.

This applies to everyone entering the MRI room; therefore the patient and accompanying adult are thoroughly checked prior to going into the MRI room. Your child may be asked to change if clothing contains metal and everyone will need to remove jewellery, hairpins, safety pins, watches and empty pockets completely. If your child has any of the following devices in situ please contact the MRI department prior to your appointment so we can identify if the device is safe to go in the scanner:

• pacemakers
• aneurysm clips
• heart valve replacements
• neurostimulators
• cochlear implants
• metal fragments in the eye
• metal foreign bodies (shrapnel)
• magnetic dental implants
• drug infusion pumps
• magnetic spinal devices

If the accompanying adult has any of the above items it is preferable another adult be available to accompany the child into the scanner, if required, as you may be deemed unsafe to go into the scanner.