What Is an MRI?
A magnetic resonance imaging test, also commonly called an MRI, is a test that employs the use of a magnetic field along with radio waves to create an image of the inside of the human body. An MRI can provide different kinds of information than normal X-rays, CT scans and ultrasound examinations. A special machine is used during an MRI and the entire process is painless. The images that are produced can be stored on computers and accessed from other locations, making an MRI an extremely useful test to help in the diagnosis of many conditions.
What an MRI Does
An MRI does not use radiation to produce an image of the body. It depends on a very powerful magnet and radio waves. The magnetic field in most MRI machines is caused by passing an electric current through a series of wire coils in the machine. Other sets of coils transmit and receive radio waves around the person in the MRI unit. A computer then can produce a series of images that depict an extremely thin slice of the body, which can be looked at from various angles by a doctor to determine if there is a problem. Diseased tissue shows up in an MRI much clearer than with other imaging tests.
Usages
The MRI can scan the brain for tumors, nerve problems, bleeding and aneurysms. Optic nerve trouble in the eyes, and nerves that are crucial to the ears, can be observed. An MRI of the chest can show the heart and surrounding vessels, along with the lungs. Blood flow through the vessels can be documented and organs such as the liver, pancreas and kidneys can be examined thoroughly. Joints and bones can be scanned and checked for arthritis and torn tendons, among other conditions. Broken bones, bulging discs and spinal problems can all be seen by an MRI examination.
The Machine
A typical MRI machine looks like a large cylindrical shaped tube that is open at both ends and encompassed by a circular magnet. A movable examination table can slide a patient into the center of the magnet where he receives instructions from the technologist operating the machine. There are short-bore MRI systems that are made so that the magnet does not go all around the patient while still others are open on all sides. MRI machines of this nature are used when a patient is either very obese or afraid of tight spaces. The station that processes the images transmitted from the MRI are in a separate room close by.
Before an MRI
Prior to having an MRI examination a patient will be asked a variety of questions about her health. Often a special contrast material is injected intravenously during an MRI exam and any potential allergies to this will be discussed, as will such topics as pregnancy and recent surgeries. People with certain conditions such as severe kidney disease may not be able to have an MRI. The patient will be wearing a hospital gown and all jewelry, watches and anything else that may contain metals such as credit cards or hearing aids are not allowed in the area of the MRI machine. People that have had metal implants can normally safely have an MRI but there are exceptions. People who have certain kinds of pacemakers and cochlear ear implants for example cannot have an MRI.
The Test
The patient will lie down on the examination table and be positioned so that the test can be started. The table will move into the MRI machine and the person will have to remain quite still. The machine produces a great deal of noises such as thumping and tapping sounds. The technologist will tell the patient to hold still as long as a few minutes and then instruct him to relax. The contrasting material is capable of making a person feel warm, but the test is normally not at all uncomfortable. The usual MRI lasts about 45 minutes to an hour and when it is completed the IV line will be removed if a contrast material was required. The patient must wait for the results from his own doctor at a later date.
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