MRI SCANNING

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Last Updated : 5/3/2010
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Dr. Ira Shah
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What is MRI ?
MRI scan is a radiological procedure that uses magnetism, radio waves for computer generated body images of internal organs.

How is MRI done ?
MRI does not depend on radiation. Instead, radio waves are directed at protons, the nuclei of hydrogen atoms, in a strong magnetic field. Since hydrogen is a part of water and water is present in each and every cell of the body. Thus, MRI can show differences in water content between various body tissues. Thus MRI can show the pathology in an organ properly and easily.

What is the procedure of MRI ?
The MRI scanner is a tube surrounded by a giant circular magnet. Patients are made to lie on a bed that slides into a donut shaped machine that encloses the magnetic tube. Some patients may feel claustrophobic during the procedure. All metallic objects on the body are removed prior to obtaining an MRI scan. Occasionally, patients will be given a sedative to decrease anxiety and relax the patient during the MRI scan. Once the scan starts there are loud, repetitive clicking noises that occur that can be quite irritating. The MRI scan time depends on the exact area of the body studied, but ranges from half an hour to an hour and a half.

The magnet creates a strong magnetic field which aligns the protons of hydrogen atoms, which are then exposed to a beam of radio waves. This spins the various protons of the body, and they produce a faint signal which is detected by the receiver portion of the MRI scanner. The receiver information is processed by a computer, and an image is produced.

What are the special precautions for MRI ?
Patients with heart pacemakers, metal implants, or metal chips or clips cannot be scanned with MRI because of the effect of the magnet.

When is an MRI scan required ?
An MRI scan is an extremely useful test for detection of pathology. A CT scan can delineate anatomy well. A PET scan can detect the function of the organs well.

MRI is useful to detect infections, bleeding, stroke, tumors, and spinal cord diseases such as intervertebral discitis, spondylitis and even paraplegia. An MRI scan can evaluate the structure of the heart and aorta, where it can detect aneurysms or tears. It provides valuable information on glands and organs within the abdomen, and accurate information about the structure of the joints, soft tissues, and bones of the body. Often, surgery can be deferred or more accurately directed after knowing the results of an MRI scan.

What are the risks of an MRI scan ?
An MRI scan is a painless radiology technique which has the advantage of avoiding x-ray radiation exposure. There are no known side effects of an MRI scan.



Contributor Information and Disclosures Dr. Ira Shah
Consultant Pediatrician, B.J.Wadia Hospital for Children, Mumbai, India


First Created : 4/9/2001
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