Tuesday, 26 July 2011

Preparing for an MRI Scan

Published in City Times

Preparing for an MRI

Rufina was apprehensive about an MRI procedure she was to undergo. Claustrophobic by nature, she feared suffocation from being ‘boxed’ inside the machine. Rufina is not alone in feeling thus. There are a number of individuals like her who are scared of being trapped inside the ‘scanner’. However, newer, patient-friendly designs of MRI machines have been developed and are beginning to be used in many parts of the world, that do not require the patient to be ‘boxed’ in. Dr.Rehab Abdallah Abdelrazig, Belhoul European Hospital, allays fears and answers questions relating to MRI.

What is MRI and does it involve any radiation?

Magnetic Resonance Imaging (MRI) is a safe and painless diagnostic technique that uses magnetic field and radio waves to create pictures of the body at different levels, without using radiation. An MRI scan uses a magnetic field to make the body’s cells vibrate which give off electrical signals to be interpreted by a computer. The scan gives very detailed images of sections of the body.

What are the indications for an MRI?

MRI may be used to make images of bones, joints, nerves, muscles, tissues and internal organs of the body. It is useful in diagnosing fractures that are not picked up on X Ray, in disorders involving the soft tissues of the body, brain, discs, nerves, ligaments, diseases of the heart and circulatory system, stroke, knee and joint disorders, et al.

Is MRI contra-indicated in certain categories of patients or for specific conditions?
Yes. Not everyone can have an MRI scan. Since the magnetic field attracts metal objects, MRI is not suitable for people who have any kind of metal implant in their body. These include cardiac patients with pace makers or those having metal prosthetic valves in their heart, patients with metal surgical clips or staples of any kind, metal pins or rods in their bones or women fitted with intrauterine contraceptive device. Pregnant women, especially, in their first trimester, are also advised against MRI. Besides, patients who have had surgery to arrest bleeding in the brain or to remove pieces of metal from their eyes, are also not suitable candidates for MRI.

How does MRI score over other diagnostic measures as X Ray, CT Scan, Endoscopy, et al?
Firstly, it is a non-invasive, painless mode of studying the internal structures of the body. Secondly, without putting the patient to any kind of risk, the structures and functions of various organs, particularly the heart, can be studies very closely and quickly. For people apprehensive of angiography, an MRI would enable specialists to examine the size and thickness of the heart chambers in order to determine the degree of damage following a heart attack or a progressive heart disorder. Also, the pumping action of the heart can be observed, thus enabling prompt action, should a blockage be seen. Unlike other scans, MRI images can be taken from almost any angle without moving the person around. It is an outpatient procedure that requires neither hospitalization nor anesthesia. However, since the procedure may take between 30 minutes to an hour, and for the duration of which the patients should remain immobile, it may be necessary to sedate them. This is particularly so, if the patient is a child.

Are there spheres where MRI may not be effective?
Though MRI is used in the detection of small fractures, MRI of bones is not as effective as CT Scan. Though CT is a single-dimension investigative modality unlike the MRI which is multi-dimensional, CT is better at picking up calcifications and early stages of bleeding anywhere in the body than the MRI.

When is a dye used in doing MRI?
Different types of tissue show up in different colours on a computer-generated image, making it easy to identify any abnormalities. A dye or contrast medium, may be injected into the area to be scanned, depending on the part of the body that is being examined. This is done with a view to make some of the tissue show up more clearly.

Does the procedure require any prior preparation?
Usually there are no specific preparations prior to the investigation, except in patients having an abdominal or pelvic scan, who should have their stomach empty for at least 4 hours prior to an MRI procedure. Every patient undergoing MRI should make sure that he/she removes any metal object such as jewelry, watch, hair clips, metal zips, hearing aids, dentures, credit cards, phone cards, before the procedure. They must wear clothing that do not have any metal objects as buttons, zips, hooks, stitched on to them. These objects, if present on the person during an MRI examination, may cause distortions in the images scanned.

How is the scan performed?
How the scan is performed will depend on the part of the body that is being examined. For instance, if scan of the head and limbs are required, only those parts of the body need to be inside the scanner. To scan other areas of the body, it is necessary to lie on a table which is then moved inside a large cylindrical tube-like structure, which generates the magnetic field. MRI images are highly sensitive to movement; hence, once the scanning procedure begins, the patient is required to lie still without moving. What can be disturbing to the patient is the loud noise, varying in pitch and volume, made by the MRI machine during the scan. But the good side is, the scanners are well lit, ventilated within and have facility to even allow you to hear music from cassettes, CD or radio. Further, the patient being scanned, may have a friend or family in the room, close to the scanner, to engage in conversation during the procedure, without making gestures. The person so entering the room should also remove any metal objects he/she may have on person.

Are there any side effects to the procedure?
MRI is a safe procedure that does not involve any negative effects. For the short period of the scan, patients may experience a slight heating, perhaps a fraction of one degree Centigrade, in the body which is highly negligible. People can resume normal activities immediately after an MRI examination. However, those who received sedation for the procedure, should ensure they are out of the sedated state before driving, etc. For patients in whom the contrast medium is used, as with any other allergen, in rare instances, they may suffer from reaction. Necessary care is taken to deal with the situation. For all other patients who have been injected the dye and have had no reactions, following MRI, they should drink plenty of water to flush the dye out of their system.


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