What is MRI?
Magnetic Resonance Imaging (MRI) is an advanced diagnostic imaging technique that produces high resolution, computerised images of the human body, sometimes in 3D. These are reported by an MRI specialist radiologist before being sent to your referring doctor. MRI scanning does not use radiation and is a painless procedure.
A very strong and uniform magnetic field is generated by a large magnet that is cylindrically shaped. The patient lies on a padded table that glides into the central opening (bore) of the magnet, with the body area being examined in the centre of the tunnel.
An antenna is placed over the body region being examined. This device (surface coil), detects a signal from the hydrogen (protons) in the water molecules of the body.
By varying the timing of radio-pulses, the spin of the protons can be altered, and information about the different characteristics of the body tissues can be determined. This gives MRI a very good ability to examine the soft tissues of the body that are rich in water content (muscles, cartilages, nerves) that other imaging techniques may not show very well.
What is MRI useful for?
An MRI can be used to examine most parts of the body including:
- Internal organs
- Brain and spine
- Blood vessels
- Bones and joints
- Pelvic contents
Is MRI for everyone?
MRI is a useful examination for most people but others who have certain metallic implants such as cardiac pacemakers or cochlea implants may be excluded from MRI scanning.
In some situations where medical devices have been implanted into the body, we will need documentation about the make and model of the device to check MRI compatibility. Please discuss all medical implants you may have with the booking staff prior to your MRI appointment.
If the patient is medically unfit to fill out the safety questionnaire, a direct family member who is aware of the patient’s entire medical history may do it for them.
If a patient does not understand English, they must bring an interpreter with them.
What does the MRI procedure involve?
Because a powerful magnet is used to obtain the images, no metal can be taken into the scan room. All patients will be asked to undress down to their underwear and will be given a gown to wear. Lockers are provided for valuables.
The MRI scan involves lying on a scan table either feet first or head first, depending on the body part being scanned, and in the majority of cases with arms by the side. A surface coil is sometimes placed over the body part being examined. The table glides into the scanner until the body part being examined is in the centre of the magnet. The machine is open at both ends throughout the MRI scan, and there is good airflow inside the machine.
MRI scans are very noisy; each scan produces loud clunking noises. For this reason ear plugs and/or headphones are used during the test.
The MRI Radiographer can communicate with the patient between scans and all patients are given a buzzer should they need to contact the Radiographer.
In some circumstances, a Contrast Injection may be used. As with any orally or injected substance, there is a minor risk that patients may suffer from a reaction to this substance.
Reactions are rare but may include:
- Low blood pressure
- Nausea / Vomiting
- Skin rash
- Anaphylactic reactions
MRI scans last between 15 and 60 minutes.
After the MRI scan, patients can resume their normal activities.
Making an appointment
When making an MRI appointment, the patient will be asked to disclose if:
- They have any electronic or metal implants or devices
- They are pregnant or breast feeding
- They have any drug or medical allergies
- They have had any recent surgery
- There is a history of metal fragments in the eyes
What to bring
Please bring all previous scans relevant to the body part being examined.