Magnetic resonance imaging (MRI) uses a strong magnetic field and radio waves to produce images. These pictures provide much more detail than traditional x-rays or CT scans. The test provides a cross-section of the area being imaged, which is then studied and interpreted by radiologists. How you are placed in the MRI and how the MRI is positioned determine the angle of the image. If you are scheduled for an MRI, you can learn how an MRI works, why an MRI is useful, and what to expect.
The Science of an MRI
An MRI functions on an atomic level. Every cell in the body contains hydrogen. Scientists discovered that when hydrogen atoms are placed in a magnetic field, they can be flipped 90 degrees. When the magnetic field is turned off, the atoms emit a tiny "squeak" of radio waves as they return to their original positions. Each tissue gives off a slightly different frequency of radio waves. A computer attached to the MRI equipment detects these different frequencies and uses them to create an image. The process of the MRI is not painful to the patient or harmful to the body.
Why an MRI?
An MRI is the diagnostic tool of choice for a variety of situations. First, it does not subject the patient to radiation, which can be important if the patient is immunocompromised or should not be exposed to even minimal amounts of radiation. All radiographic studies must balance patient comfort with speed of testing and level of detail provided. An MRI is generally comfortable for the patient (the most common complaint is claustrophobia), can take place in about an hour, and provides a considerable level of detail. MRIs can help detect brain tumors and aneurysms in the brain and can help gauge the extent of trauma to the head.
As a Patient
If you are scheduled for an MRI of the brain, you may or may not be asked to refrain from eating or drinking before the test. You will be asked a number of questions to determine whether an MRI is a suitable diagnostic tool for you. Be sure to inform your doctor if you are pregnant, if you have an IUD, if you have a pacemaker or other surgical implant, or if you have any metal in your body. If you are claustrophobic, your doctor may schedule you for an open MRI or provide you with medication that will help you relax during the procedure. (A traditional MRI is shaped much like a very large test tube, and most of your body will be inside the tube. An open MRI is more like a doughnut: much less of your body will be enclosed.) When you arrive at the testing location, you will again be asked a series of questions to confirm that the procedure is safe for you. You may or may not have an i.v. started; if you are having an MRI with contrast, you will probably receive an i.v. You will be asked to remove all jewelry, any glasses, removable dentures, and so forth, before you enter the testing room. Once in the room, you will lie down on a sliding table. A machine called a surface coil will be placed around your head. The technician will then slide you into the MRI machine. The technician will leave the room and the test will begin. The hardest part of the MRI then begins: you have to lie completely still when the test is underway. MRIs can be very loud depending on the particular model being used. The technician will be able to talk with you during the test via intercom. The test usually takes between 30 and 60 minutes. After the test, the technician will remove you from the machine and help you sit up. If you received an i.v., it will be discontinued. After this, you will be finished and can return home.
Tags: technician will, magnetic field, radio waves, your body, body will, diagnostic tool, level detail
