Magnetic Resonance Imaging: Having an MRI Scan

An MRI scan is an examination performed to provide more information about any medical conditions you may have or to identify various diseases or injuries. An MRI scan is reviewed and reported on by a neuroradiologist to provide your doctor or clinical nurse specialist with a diagnosis.

An MRI scanner uses a magnetic field and radiofrequency pulses to move and manipulate the protons of hydrogen atoms in your body in and out of line with the magnetic field. This causes the protons to spin and produce a signal, which is detected by a special coil. This coil is placed over the area being scanned. The signal produced will be different for each tissue type (fat, muscle, bone etc.).

A computer then processes the information received by the coils to produce an image. Figure 1 demonstrates what an MRI scanner looks like.

MRI is used to visualise and distinguish selected areas of the body from surrounding tissues. MRI is particularly good for looking at muscles and soft tissue structures, such as the brain.

An MRI scan can also help your doctor plan or carry out future treatments.

All treatments and procedures have risks and we will talk to you about the risks of an MRI beforehand. If you have been referred for an MRI scan with a contrast injection (gadolinium) then there are other risks, including potential allergic reaction.

Please see our leaflet ‘Contrast Agents for MRI Examinations: An Information Guide’ for further information.

Problems that may happen straight away

You will notice once the scan begins it is very loud; this noise is created due to the magnetic fields. We will provide you with earplugs and ensure these are fitted correctly before starting the scan. Occasionally some patients may get peripheral nerve/muscle stimulation during the scan, e.g. pins and needles or twitching in your fingertips. This is normal and should subside shortly after your scan. We will provide you with a call button, which you can press at any time if you cannot tolerate the noise or do not wish to continue the scan.

Problems that may happen later

If your scan is particularly lengthy you may start to feel slightly warm. This is due to the radiofrequency energy applied during the scan and how the molecules in your body react to this. You will be monitored throughout your scan by the radiographers and may stop the scan if you do not feel well.

Problems that are rare, but serious

Currently there is no evidence to suggest MRI scans cause any long-term or serious effects.

Pregnant patients

If think you might be or are currently pregnant, please contact neuroradiology prior to your scan. To ensure the scan is absolutely necessary, your referring doctor or clinical nurse specialist and a consultant neuroradiologist will need to have a discussion of the risks and benefits. They may decide to postpone the scan. This is due to the acoustic noise from MRI and its potential unknown effects on the hearing of your unborn child.

If you do not wish to have an MRI, this is your choice and you will not be treated any differently and this will not influence any other aspect of your care. It may mean, however, that your doctor or clinical nurse specialist cannot be as certain or specific about any future treatment or diagnosis.

Your doctor or clinical nurse specialist will have taken into account the potential risks and benefits of having an MRI when referring you to neuroradiology.

There may be some alternative scan methods in CT or ultrasound, the possibility of these should be discussed with your referring doctor or clinical nurse specialist first.

Please contact neuroradiology prior to your scan if you: 

• Require hospital transport or hoist assistance  
• Require an interpreter, please let us know what language you speak
• Are currently pregnant
• Have ever had any of the following implanted:
  • Cardiac Pacemaker
  • Coronary (heart) stents  
  • Artificial Heart Valve
  • Nerve stimulator within the brain (vagus/occipital)
  • Deep brain stimulator
  • Spinal column or sacral nerve stimulator
  • Drug infusions pump (baclofen or others)
  • Cochlear implant
  • Programmable shunt
  • Metal in or near your eyes previously
  • Any operations in the last six weeks involving metallic implants

Eating and drinking guidance

• Continue to eat and drink as normal before and after your scan
• If you have been told your scan is to be performed under general anaesthesia then please refer to the ‘Magnetic Resonance Imaging (MRI) under general anaesthesia’ patient information leaflet or speak with your referring doctor or clinical nurse specialist

Medication Guidance

• Take medications as normal, before and after your scan, unless advised otherwise
• Contact neuroradiology if you are unsure about any of your medication

If possible, aim to arrive shortly before your appointment to give the staff time to prepare you for your scan or procedure. You will be asked to remove all metal objects from your person which you will be able to place in a secure locker within the department. If some of your clothes contain metal, such as zips, poppers, chains, you may be asked to change into a hospital gown.

Please avoid heavy eye make-up or make-up containing glitter if possibly as these can produce an artefact on your scan and degrade image quality.

You should avoid wearing clothes that contain metal for your MRI. Please bring suitable clothes to change into or we can provide you with a hospital gown.

You can wear:

• t-shirts
• leggings
• tracksuits
• pyjamas

You should not wear:

• a bra
• jeans
• a belt
• clothing with zips or poppers
• hairclips

A radiographer will go through your MRI Safety Questionnaire and answer any questions you may have. Please try to complete this questionnaire prior to your appointment. You may also fill this in on-line via UCLH’s MyCare.

The length of your examination will vary depending on the type of scan you are having, please see your appointment letter for further information.

If you plan to take oral sedation for anxiety or claustrophobia before your MRI, please arrive 30 mins before your appointment time, this will give staff time to ask you the safety questions before you take any sedation and give the medication time to take effect, whilst you are in a safe environment. We do not provide sedation in the department; this must be prescribed by your GP before your scan.

We want to involve you in all the decisions about your care and treatment. If you decide to go ahead with this examination, by law we must ask for your consent. This confirms that you agree to have the procedure and understand what it involves. Staff will explain all the risks, benefits and alternatives before they ask you to verbally consent to proceed. If you are unsure about any aspect of your proposed examination, please don’t hesitate to speak with a senior member of staff again.

You will be asked to lie flat on the scanner table; we will provide cushioning to protect your back or any other areas you feel require extra support. Please ensure you wear comfortable clothing. The radiographer will help you place single-use earplugs, provided by the trust (please do not bring your own) and will give you a call button that allows us to know if you wish to stop the scan.

The radiographer will slowly move you into the scanner which is open at both ends, ensuring you are safe and reassured. The scanner has strip lights along the length of it and a fan to make the scanner more comfortable and patient friendly. The radiographer will speak to you during the examination and we will visually monitor you closely throughout. 

Scan times can vary depending on the area(s) we are scanning. The radiographer can tell you approximately how long your scan will take beforehand and can give you updates throughout if you wish, this may be subject to change during your scan if you move or we require further imaging.

In some scanners we have small mirrors attached to the head coils, which similar to a periscope; let you see out of the scanner. We can also play music through the speakers in the scanner if you wish. It is very important you remain still during your scan, to ensure we obtain good quality images.

Once your scan is complete you will be free to go home, or continue to attend any other appointments. A consultant neuroradiologist will review your scan and prepare a formal report. This report will be sent to your referring doctor or clinical nurse specialist, the results of which will be available for your next consultation.

• NHS Direct is a useful source of health information (https://www.nhs.uk/conditions/mri-scan/what-happens/)
• The NHS Clinical Knowledge Summaries website (www.cks.nhs.uk)

UCLH cannot accept responsibility for information provided by other organisations.

• NHS. 2018. How it's performed - MRI scan. [Online]. [18 June 2020]. Available from: www.nhs.uk/conditions/mri-scan

Lysholm Department of Neuroradiology
National Hospital of Neurology and Neurosurgery,
Queen Square,
London WC1N 3BG

Email: uclh.enquiry.nhnmrapp@nhs.net
Direct line: 020 344 83440
Switchboard: 0845 155 5000/ 020 3456 7890
Extension: 83440/ 83103
Fax: 020 344 84723

The Lysholm Department of Neuroradiology reception is located in Chandler Wing, on the lower ground floor of the National Hospital for Neurology & Neurosurgery, Queen Square. Please turn left when you exit the Chandler Wing lifts on the lower ground floor to find our main neuroradiology reception.