COMMON DIAGNOSTIC TESTS

MRI (Magnetic Resonance Imaging)

Unlike x-ray tests which use ionizing radiation, magnetic resonance imaging is a diagnostic system using electromagnetic radio waves. An MRI displays images of the body in "slices" similar to that of a CAT scan but it is also able to reflect greater contrast between different types of body tissues.

How an MRI works
In order to start the testing procedure, the patient will be asked to remove all metal objects such as jewelery and body piercings as these may pollute the image. If metal objects exist internally, the patient's physician and/or radiologist should be informed. Once all metal objects are removed, the patient lies on a table which slides into the opening of a circular machine. This narrow, open-ended and tube-shaped machine is where a powerful magnetic field will penetrate the patient's body. The hydrogen atoms within the patient's body react to the magnetic field and align themselves accordingly. Radio waves which are also emitted are absorbed by the area of focus and then transmitted back as a signal. This signal is analyzed by a computer and processed into images of the body. In some cases, a contrast dye is given to produce clearer images of an area. Either the physician or the radiologist will inform the patient if this is necessary.

Some patients may experience discomfort due to being in a closed-in space. If the patient feels intensely claustrophobic, a mild sedative may be given to induce relaxation. Another alternative is for the patient to have an open MRI test done. An open MRI, a new development in diagnostic testing, uses the same diagnostic imaging techniques as a traditional MRI except it allows for more room around the patient's body. A physician will make an assessment as to whether this option should be made available to the patient.

While the test is in process, the patient should keep very still and maintain a consistent breathing pattern. A rhythmic knocking noise will be heard as shifting in imaging sequences occur and magnets are turned on and off.

What an MRI looks at
An MRI is best at imaging soft tissue structures including areas in:

Did you know . . . ?
Radio waves, which are used in magnetic resonance imaging, are also used in microwaves to heat food. The difference between these two systems is the frequency of the radio waves, which are higher in microwaves.