MRI scan

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What is MRI scan?

MRI (magnetic resonance imaging) is a fairly new technique that has been used since the beginning of the 1980s.

The MRI scan uses magnetic and radio waves, meaning that there is no exposure to X-rays or any other damaging forms of radiation. The patient lies inside a large, cylinder-shaped magnet. Radio waves 10,000 to 30,000 times stronger than the magnetic field of the earth are then sent through the body. This affects the body's atoms, forcing the nuclei into a different position. As they move back into place they send out radio waves of their own. The scanner picks up these signals and a computer turns them into a picture. These pictures are based on the location and strength of the incoming signals.

Our body consists mainly of water, and water contains hydrogen atoms. For this reason, the nucleus of the hydrogen atom is often used to create an MRI scan in the manner described above.

Using an MRI scanner, it is possible to make pictures of almost all the tissue in the body. The tissue that has the least hydrogen atoms (such as bones) turns out dark, while the tissue that has many hydrogen atoms (such as fatty tissue) looks much brighter. By changing the timing of the radiowave pulses it is possible to gain information about the different types of tissues that are present.

An MRI scan is also able to provide clear pictures of parts of the body that are surrounded by bone tissue, so the technique is useful when examining the brain and spinal cord.

Because the MRI scan gives very detailed pictures it is the best technique when it comes to finding tumours (benign or malignant abnormal growths) in the brain. If a tumour is present the scan can also be used to find out if it has spread into nearby brain tissue.

The technique also allows us to focus on other details in the brain. For example, it makes it possible to see the strands of abnormal tissue that occur if someone has multiple sclerosis and it is possible to see changes occurring when there is bleeding in the brain, or find out if the brain tissue has suffered lack of oxygen after a stroke.

The MRI scan is also able to show both the heart and the large blood vessels in the surrounding tissue. This makes it possible to detect heart defects that have been building up since birth, as well as changes in the thickness of the muscles around the heart following a heart attack. The method can also be used to examine the joints, spine and sometimes the soft parts of your body such as the liver, kidneys and spleen.

The scan is usually done as an outpatient procedure, which means that the patient can go home after the test. During the scan it is important to lie completely still. For this reason it might be necessary to give a child an anaesthetic before they are tested.

Since you are exposed to a powerful magnetic field during the MRI scan, it is important not to wear jewellery or any other metal objects.

It is also important for the patient to inform medical staff if they use electrical appliances, such as a hearing aid or pacemaker, or have any metal in their body such as surgical clips, but orthopaedic metalware such as artificial hips or bone screws is not normally a problem.

There are no known dangers or side effects connected to an MRI scan. The test is not painful; you cannot feel it. Since radiation is not used, the procedure can be repeated without problems. There is a small theoretical risk to the foetus in the first 12 weeks of pregnancy, and therefore scans are not performed on pregnant women during this time.

Because patients have to lie inside a large cylinder while the scans are being made some people get claustrophobic during the test. Patients who are afraid this might happen should talk to the doctor beforehand, who may give them some medication to help them relax.

The machine also makes a banging noise while it is working, which might be unpleasant.

How does an MRI scan differ from a CT scan?

With an MRI scan it is possible to take pictures from almost every angle, whereas a CT scan only shows pictures horizontally. There is no ionizing radiation (X-rays) involved in producing an MRI scan. MRI scans are generally more detailed, too. The difference between normal and abnormal tissue is often clearer on the MRI scan than on the CT scan.

( Courtesy: Dr Sarah Burnett, consultant radiologist and Dr John Pillinger, GP, Net doctor www.netdoctor.co.uk )

More....

What is an MRI?

MRI (Magnetic Resonance Imaging) is a noninvasive diagnostic tool used to identify and treat various medical conditions. These exams provide unparalleled views of internal body structures including the organs, soft tissues and bone, which cannot be seen using conventional X-rays or CT scans.

MRI technology produces clear and precise cross-sectional images. This diagnostic tool offers a quick and safe method for gathering pictures of the human anatomy allowing physicians to detect many conditions in earlier stage
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How does an MRI work?

MRI technology uses a magnetic field and radio waves to produce detailed pictures of the human body. As the radio waves pass through the body, images are created on a computer screen for radiologists to analyze. These precise images allow radiologists to view soft tissue (muscles, fat, internal organs, blood vessels and tendons) and bones without the use of X-rays or surgery
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Is an MRI safe?

The MRI imaging technique does not involve exposure to radiation. However, women should always inform their technologist if there is a chance they could be pregnant. Medical and electronic devices may interfere with MRI exams and pose a potential risk. Patients with any kind of metallic implant should not have an MRI unless their physician is aware of the device and has approved the procedure. Patients with pacemakers should not undergo an MRI.
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What if I am claustrophobic and don't like to be in enclosed spaces?

The MRI team will work with patients who suffer from claustrophobia. Patients can come before their appointment and tour the facility to become better acquainted with the scanning process.

Satellite radio is provided in the MRI suite to help patients relax during their scan. A friend or family member (who has been screened for internal or external metal) may also accompany the patient into the exam room during the test.

Many patients request a mild sedative prescription from their physician prior to their appointment and arrange for a responsible adult to drive them home.
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Can pediatric patients receive an MRI?

Yes, children can receive an MRI. The Radiology Department has specialty radiologists and a conscious sedation program to meet the unique needs of pediatric patients.

Parents can accompany their children into the scan room and remain with the child during the MRI exam. A Child Life Specialist is available upon request.
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Should I take my medications the day of my MRI?

Yes, it is important for patients to continue taking all medications prescribed by their physician before their MRI exam. Patients should let their technologist know what medications they have taken prior to their MRI scan.
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Can I eat and drink before my MRI?

Patients will receive individual instructions about eating and/or drinking from a member of the MRI Department prior to their scan.
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How should I dress for my MRI?

Patients should dress in loose-fitting, comfortable clothing such as a sweatshirt and pants without metal snaps or zippers. All valuables should be left at home.

Jewelry, glasses, hearing aides, dentures, hairpins, credit cards, coins, keys and other metal objects will need to be removed and placed in a safe location outside the scan room. Secure clothing lockers are provided for patients during their MRI scan. Patients are also advised not to wear cosmetics to their scan as many brands contain metal.
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Will I receive an intravenous drip during my MRI?

Depending on the type of exam, patients may receive a contrast agent intravenously (IV) through a vein in the arm or hand. Contrast mediums or contrast agents are safe injections used to highlight organs and blood vessels to help produce a better image for the radiologist.

If your physician or radiologist has determined that an IV will enhance your MRI scan results, you will receive an IV in your arm or hand prior to the test so the technologist can administer the contrast agent at the time of your scan.
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What happens during my MRI?

When you are ready for your scan, a technologist will bring you into the MRI scan room and help you get comfortable on the padded examination table. The table will then move slowly into the opening of a large cylinder-shaped tube that houses the MRI magnet. You will hear a continual knocking noise while the machine takes pictures.

Earplugs are provided and significantly reduce the amount of noise during the scan. It is important to lie completely still while the images are being taken because motion will effect the sharpness of the image. The technologist will talk with you throughout your scan and keep you informed of what you can expect.
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How long will my MRI scan take?

MRI scans are individualized and tailored to each patient's needs. Total scan times range from 20 to 60 minutes.

Patients who require a contrast agent will be given the IV injection after their preliminary scans. The patient will then return to the examination table to continue the scan. Pictures are needed before and after the IV injection when a contrast agent is used.

After the technologist completes the MRI scan, they will review all of the images to make sure they have complete information for the ordering physician.
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What happens after my MRI?

Patients may leave immediately following their MRI scan and can go about their normal activities. Radiologists at Newton-Wellesley know that rapid results are essential for each patient's peace of mind and so physicians can begin planning treatment immediately.

After each MRI scan, a Newton-Wellesley radiologist reads the images in a timely manner. The Hospital has advanced, high-tech capabilities to provide physicians with fast MRI exam results.