What is an MRI?
Magnetic resonance imaging or MRI is defined by the American College of Radiology as one of the newest and most exciting fields of medical imaging. The MRI produces an image that is like a visual "slice" of anatomy and is capable of generating an infinite number of images throughout the body.
During an MRI, a large magnet, with a magnetic field 60,000 times greater than the earth's magnetic field, surrounds the patient. Radio frequencies and a computer are used to produce the images.
The body is made of particles called atoms. The center of the atom are nuclei that normally spin at different angles. When the magnetic field hits the nuclei, they begin to spin at the same angle. A radio signal, which temporarily changes the nuclei alignment, is sent out. When the signal is stopped, the nuclei return to the aligned position and release a faint radio frequency of their own. The frequency is recorded by the computer and processed into a detailed image of the human body.
Using MRI, physicians can see the brain and tiny nerves that make up the spinal cord. Because of this clarity, the MRI is often used to examine the brain, neck, and spinal cord.
Patients with cardiac pacemakers, metallic clips in the brain and other metallic foreign bodies in the eye area cannot undergo an MRI.
Preparing for the MRI
Your doctor will give you instructions on how you should prepare for the MRI. Follow any instructions about eating or taking medications that your physician may have given you.
What to Expect During the MRI
When you enter the scanning area, a technician will help you on the scanning table and will get you positioned correctly. Most often, you will be lying on your back. If a contrasting agent is necessary for the study, you will be given an injection. If the injection makes you feel sick or if you feel uncomfortable, you need to tell the technician.
As the scan begins, the table will slide into the magnet, which looks like a tunnel with both ends open. If you are uncomfortable with the close space or noises the equipment makes, you may signal the technician who may be able to help you deal with these feelings.
During the procedure, it is important to stay still. You will not feel any pain or pressure during the scanning. However, there will probably be knocking and thumping sounds as the machine works. You may want to wear earphones and listen to music during the procedure.
When the scan is finished, the images will be reviewed, and if there are no problems, the test is completed. If you have been sedated, you will need to stay until your physician indicates you may leave.