The MRI Scan

As taken from the BUPA fact sheet

MRI scan
This factsheet is for people who are considering having an MRI scan or for people who would like information about MRI scans.
A magnetic resonance imaging (MRI) scan is a special technique that uses magnets and radiowaves to produce two and three-dimensional pictures of the inside of the body. These images can help your doctor to make a diagnosis about a number of conditions.

About MRI
The magnetic field produced by an MRI scanner allows radio receivers (placed close to the body) to detect tiny signals from inside the body. A computer turns these tiny signals into two or three-dimensional pictures.
MRI may be used to make images of many parts of the body. Different types of tissue show up in different shades of grey on a computer-generated image. Abnormalities can be seen as darker or lighter areas in some tissues.
Depending on the part of the body being examined, having an MRI scan may involve being enclosed in a fairly narrow space. If you are worried about this aspect of the scan you should speak to your doctor in advance. Having an MRI scan does not hurt. It does not use X-rays and you are not exposed to radiation.

Illustration showing an MRI scanner

Why have an MRI scan?
An MRI scan can help a doctor make a diagnosis and has many uses including:
orthopaedic examinations screening and assessing cardiac conditions brain imaging to find the cause of a stroke, for example detecting suspected abnormalities in the body such as abscesses, abnormal blood vessels and tumours pinpointing the exact site of tumours before radiotherapy

Who can have an MRI scan?
Not everyone can have an MRI scan. The magnetic fields and radiowaves can seriously affect implants of metal in the body. This includes anyone who has: a heart pacemaker a cochlear implant (an internal hearing aid) metal heart implants such as prosthetic metal valves
metal surgical implants such as surgical clips or pins or rods in bones surgical implants to stop bleeding in the brain had pieces of metal removed from their eyes (due to welding or metalwork for example)

Can pregnant women have an MRI scan?
An MRI is not usually performed on pregnant women unless there is an urgent medical reason for the scan. This is because the long-term effects of strong magnetic fields on a developing baby are not yet known.

What are the alternatives?
Generally speaking, MRI provides a more detailed soft tissue image than other scans, such as a CT scan.
In some cases, depending on individual factors such as your symptoms and the specific condition being investigated, there may be alternatives to having an MRI scan. These include:
an ordinary X-ray a CT (computerised tomography) scan - for more information please see the separate BUPA factsheet, CT scan ultrasound a nuclear medicine scan which uses radioactive tracers to create images

What happens before the scan?
An MRI scan is usually performed in a hospital. In many cases no preparation is required.
Before the MRI scan you will usually talk to your radiologist or radiographer about the scan and you may be asked to sign a consent form. This confirms that you understand the risks, benefits and possible alternatives to the procedure and have given your permission for it to go ahead. You may also be asked to fill out a questionnaire which will ensure that it is safe for you to have the scan.
Some types of metal can interfere with the scan, so you will be asked to remove metal objects such as coins, keys, and jewellery. It is best to wear clothing that does not have metal zips, buttons or other metal parts such as underwired bras. Relatives or friends who wish to accompany a patient in the MRI room must also follow these guidelines.

The scan
An MRI scan is performed as a day case, which means that you can have the scan and go home the same day. An MRI scan is painless so the procedure does not usually require an anaesthetic. However it can be uncomfortable lying still for this length of time, particularly if you have a painful condition, so you may be offered a sedative which will relax you.
Small children may also be offered a sedative and sometimes a general anaesthetic.
The scan itself can take from 15 minutes to an hour to perform, depending on the specific examination, but you should allow at least two hours for the whole appointment.
You will lie on a table which will be moved inside a large "tube", which generates the magnetic field. You may need to enter the tube head-first or feet-first depending on the part of your body that is being scanned. Generally the part of your body to be examined will be placed in the middle of the tube. The tube is open ended so you will not be enclosed at any time.
A radiographer operates the scanner from behind a window, and will be able to see and hear you throughout the procedure. You may be given a call button to hold during the scan which you can press to get the radiographer's attention at any time.
It can take several minutes for each picture to be taken, and it's important to lie very still and breathe quietly during the process. The machine will make quite a loud knocking or buzzing sound so it may help to wear earplugs. In some units, music is played to help you relax. When the scan is complete, the table will be moved back out from the scanner.

What to expect afterwards
Once the examination is over, most people can resume their normal activities immediately. However, if you have had a sedative, you will need to arrange for someone to drive you home and then stay with you for the first 24 hours.
The pictures taken by the MRI scanner will be interpreted by a radiologist, who will send the results to your doctor or specialist.

Deciding whether to have an MRI scan
An MRI scan is a commonly performed and safe procedure. For most people, the potential benefit is greater than the disadvantages. However, in order to make a well-informed decision and give your consent, you need to be aware of the possible side-effects and the risk of complications.
Side-effects are the unwanted but mostly temporary effects of a successful procedure. The MRI scan itself does not usually have any physical side-effects. However, if a contrast medium is used, you may experience a temporary flushing when you are given the injection. This usually passes within seconds. People who have metal fillings in their teeth may also feel a tingling during the scan.
Complications are unexpected problems that can occur during or after the procedure. Most people are not affected. Complications that may arise from an MRI scan are related to the contrast medium, and include an allergic reaction to the dye. Different people may have different reactions to the dye - let the radiographer know if you feel uncomfortable or are short of breath during the scan. Allergic reactions happen only occasionally and can be treated immediately with appropriate medicines.

My Opinion of the MRI
I have now had 3 MRI scans and have found no problems with these at all. They are straight forward and over in the space of 15mins. For the Lumbar region you do not need to stop eating before it and you don,t have any injections. It is a simple case of get changed into a gown,lie on a table that moves into the enclosed area listen to a few bangs and you are back out and off home.