MRI (Magnetic Resonance Imaging) is a type of scan that uses a very strong magnetic field and radio-waves to produce detailed inages of the inside of the body. It works by receiving a signal from the hydrogen protons within you. Powerful computers then turn this signal into an image. It has the ability to see soft tissue very clearly, including brain, muscle, organs, nerves, blood vessels, and even bones.
What can I expect?
Depending on which part of the body is being scanned, the scan can take anything from 10 minutes to 1 hour. A small injection of a type of dye is occasionally given in the arm in order to gain different pictures.
You will be asked to fill in a safety questionnaire, as not all patients are suitable for this test. A member of staff will go through this with you. You will be required to remove any metallic objects about your person although certain items of jewellery are sometimes allowed. You may also be asked to change into a gown.
You will then be placed in the scanner and made comfortable. It is very important that you try to keep still, as any movement can degrade the images. You will be given earplugs or headphones as the scanner is noisy, but you will still be able to hear and talk to the staff.
Is MRI safe for everybody?
If there is any material present inside the body that is affected by a magnetic field we may not be able to do your scan.
Please inform us as soon as possible if you have or have ever had any of the following:
- A heart pacemaker
- Artificial heart valves
- Clips from surgery within the last eight weeks
- Aneurysm clips in your head
- Inner ear implants
- Metal fragments within your eye or head
- Neuroelectrical stimulators.
Please let us know if you think you may be pregnant or you suffer from severe claustrophobia.
Metallic objects in your pockets and credit cards will be affected by the magnetic field and should not be taken into the MRI room. Changing facilities are available, with lockers for valuables. It is not usually necessary to remove wedding rings.
What happens after the scan?
There are no side effects and you may return to work or drive immediately after.
The results will be sent to your consultant within a few days or your GP within 10 days.
If you have any queries about your scan or wish to change your appointment, please contact the individual MRI departments.
Medical information for MRI patients
Stress cardiac perfusion examination
Stress cardiac perfusion examination is only performed at Grantham and District Hospital
Using MRI, we can take very detailed pictures of the heart. The scan shows how well your heart is pumping and if any areas appear under strain. A special dye called gadolinium is also often used to show the supply of blood to the heart and to look for the presence of any scar tissue. This information can be used to diagnose heart conditions and to help plan treatment.
Pictures will be taken at rest and when the heart is exercising since any affected areas of the heart show up even better under these circumstances. As there is not room to physically exercise in the scanner we will exercise your heart artificially using a drip containing a drug called dobutamine or adenosine which will be given into a vein in your arm. Both these agents are commonly used and are well tolerated – you may have had a test that has used them already. Very few patients have reported side effects but these may include tingling, headache, heart rhythm disturbances, chest pain and nausea.
- You will be monitored by a doctor throughout the infusions who will stop the procedure immediately if you develop any heart tracing changes, side effects or at your request.
- The scan will require you to lie still on a couch within the bore of a very large magnet.
- One small cannula will be put into a vein in your arm via a small needle for the exercising agent, and one will also be put in for the dye.
- You will be asked to hold your breath for some of the scans for about 10-15 seconds. When the pictures are being taken you will hear a sound like a loud foghorn.
- Your blood pressure and pulse will be taken regularly during the scan.
- Electrical heart tracings will also be taken.
- The whole procedure takes about one hour.
You must avoid caffeine for 12 hours prior to your appointment. This includes tea, coffee, chocolate, fizzy drinks etc.
If you have ever suffered from asthma, please telephone us on 01476 464880 as this may affect your appointment.
After the scan, you will be able to eat and drink normally.
MRI arthrogram
This is an examination to diagnose problems within a joint using the MRI scanner with the help of a contrast agent. Most commonly used for the shoulder, wrist or hip.
This is a two part examination using both an x-ray screening room and the MRI scanner. You will first be taken to an x-ray screening room where local anaesthetic will be injected into an area around the joint to be imaged. Once this has taken affect the contrast agent, which shows on the MRI scans, will be injected into the joint. An adiologist will undertake this part of the examination.
For the second part of the examination you will be taken to the MRI scanner where the images are taken to show areas of the joint highlighted by the contrast agent. You should allow up to two hours for the complete procedure as there may be a small interval between the injection of the contrast and performing the scan.
After the procedure, you may have mild symptoms of pain at the needle puncture site and an increase in joint stiffness, with a feeling of fullness in the joint. For this reason it is important to bring someone with you who can drive you home after the procedure. These symptoms will last no more than two or three days, but occasionally can last up to 10 days. They respond to rest and simple pain relieving medicine. With any injection there is a very slight risk of infection. You will be told what to look for and how to deal with any problems if they arise.
Contrast agents (dyes)
Occasionally, a contrast agent (often termed a dye) needs to be injected to give us different information on the images. This agent is used to enhance certain tissues or areas that can be difficult to see, or to characterise other tissues and help produce a more accurate diagnosis. If you are asked to have this, it is important that it is given in order to improve the result.
The injection is generally called Gadolinium as this is its main ingredient. It is a very safe injection, and there are rarely side effects, but as with any medicine, some people can be allergic to the ingredients. We use four different types of Gadolinium, depending on what anatomy we wish to see better.
Contact details
The booking office is open Monday to Friday 8.30am to 5pm and can be contacted by calling 01476 464880.