MRI

Magnetic Resonance Imaging (MRI) is the most advanced imaging technology available today. MRI is generally considered safer than other imaging techniques because it is noninvasive and because it does not employ x-rays. MRI uses radio waves and a powerful magnet to create images of internal organs and tissue. This test is frequently used when findings on a CT scan are not clear.

During the imaging process, the magnet excites the hydrogen atoms in the body's cells. In turn, these hydrogen atoms give off tiny electrical charges that are picked up by a scanner and assembled into images. It takes a series of images to build a picture of the isolated area. MRI is particularly sensitive to liver tissue and is capable of displaying liver vasculature without the need of a dye.

The following images are from a patient with colorectal liver metastases. The first is a CT scan that suggests a subtle abnormality (indicated by arrow). The second image is an MRI scan which shows three separate areas (indicated by arrows) of liver metastases.

MRIs are usually done on an outpatient basis in a clinic. The patient lies down on a table that slides into the tunnel-like MRI machine. Patients who are claustrophobic may experience difficulty with this device. During this test, the patient must remain relaxed and very still. The machine itself makes a loud knocking sound that can be bothersome. Some MRI Imaging facilities now allow patients to bring portable CD or cassette tape players with them to listen to music during the test.

A new model of MRI machine, called Accessible or Open MRI, no longer surrounds the patient in a tunnel. This makes the experience more tolerable to people who experience claustrophobia. An open MRI is frequently used in the diagnostic treatment of cancer patients at Allegheny General Hospital.