Cape Town MRI | FAQ
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FAQ

What happens during an MRI scan

During an MRI scan, you lie on a flat bed that’s moved into the scanner. Depending on the part of your body being scanned, you’ll be moved into the scanner either head first or feet first.

The MRI scanner is operated by a radiographer, who is trained in carrying out imaging investigations. They control the scanner using a computer, which is in a different room, to keep it away from the magnetic field generated by the scanner.

You’ll be able to talk to the radiographer through an intercom and they’ll be able to see you on a television monitor throughout the scan.

At certain times during the scan, the scanner will make loud tapping noises. This is the electric current in the scanner coils being turned on and off. You’ll be given earplugs or headphones to wear.

It’s very important to keep as still as possible during your MRI scan. The scan lasts 15 to 90 minutes, depending on the size of the area being scanned and how many images are taken.

How does an MRI scanner work?

Most of the human body is made up of water molecules, which consist of hydrogen and oxygen atoms. At the centre of each hydrogen atom is an even smaller particle, called a proton. Protons are like tiny magnets and are very sensitive to magnetic fields.

When you lie under the powerful scanner magnets, the protons in your body line up in the same direction, in the same way that a magnet can pull the needle of a compass.

Short bursts of radio waves are then sent to certain areas of the body, knocking the protons out of alignment. When the radio waves are turned off, the protons realign. This sends out radio signals, which are picked up by receivers.

These signals provide information about the exact location of the protons in the body. They also help to distinguish between the various types of tissue in the body, because the protons in different types of tissue realign at different speeds and produce distinct signals.

In the same way that millions of pixels on a computer screen can create complex pictures, the signals from the millions of protons in the body are combined to create a detailed image of the inside of the body

Who can and cannot have MRI Scans

Magnetic resonance imaging (MRI) is very safe and most people can have the procedure, including pregnant women and babies.

However, there are some instances where an MRI scan may not be recommended, because the strong magnets used during the scan can affect any metal implants or fragments in your body.

Before having an MRI scan, you should tell medical staff if:

 

you think you have any metal in your body

you’re pregnant or breastfeeding

There’s no evidence to suggest MRI scans pose a risk during pregnancy. However, as a precaution, MRI scans aren’t usually recommended during pregnancy, particularly in the first three months.

Metal implants or fragments

Having something metallic in your body doesn’t necessarily mean you can’t have an MRI scan, but it’s important for medical staff carrying out the scan to be aware of it.

They can decide on a case-by-case basis if there are any risks, or if further measures need to be taken to ensure the scan is as safe as possible. For example, it may be possible to make a pacemaker or defibrillator MRI-safe, or to monitor your heart rhythm during the procedure.

If you’re unsure about any metal fragments in your body, you may need an X-ray

www.nhs.uk

Some examples of metal implants or fragments include:

 

a pacemaker www.nhs.uk – an electrical device used to control an irregular heartbeat

an implantable cardioverter-defibrillator (ICD) –a similar device to a pacemaker that uses electrical shocks to regulate heartbeats

metal plates, wires, screws or rods – used during surgery for bone fractures

a nerve stimulator –an electrical implant used to treat long-term nerve pain

a cochlear implant –a device similar to a hearing aid that’s surgically implanted inside the ear

a drug pump implant –used to treat long-term pain by delivering painkilling medication directly to an area of the body, such as the lower back

brain aneurysm clips –small metal clips used to seal blood vessels in the brain that would otherwise be at risk of rupturing (bursting)

metallic fragments in or near your eyes or blood vessels (common in people who do welding or metalwork for a living)

prosthetic (artificial) metal heart valves

penile implants –used to treat erectile dysfunction (impotence)

www.nhs.uk

eye implants –such as small metal clips used to hold the retina in place

an intrauterine device (IUD) www.nhs.uk –a contraceptive device made of plastic and copper that fits inside the womb

artificial joints – such as those used for a hip replacement www.nhs.uk or knee replacement www.nhs.uk

dental fillings and bridges

tubal ligation clips –used in female sterilization www.nhs.uk

surgical clips or staples – used to close wounds after an operation

Tattoos

Some tattoo ink contains traces of metal, but most tattoos are safe in an MRI scanner. Tell the radiographer immediately if you feel any discomfort or heat in your tattoo during the scan.

Could you have metal fragments in your eyes
How long does an MRI scan take?

The scan can take anything between 20 minutes and 90 minutes depending on the area of the body being imaged. Most protocols takes about 45 minutes, which are divided into separate blocks of scans. The machine will “run” for roughly 5minutes at a time, and will then stop. During the stopping period we can communicate with the patient using a two way communication system. It is however very important to keep very still during the scan to ensure optimal image quality and avoid repeating certain “blocks”.

Who interprets the results and how do I get them?

A Radiologist will analyse the images and send a signed report to your primary care or referring physician, who will then share the results with you.