What is an MRI scan?

Video: How an MRI works

An Magnetic Resonance Imaging (MRI) scan uses radiofrequency waves and a strong magnetic field rather than X-rays to image the body's internal structures, organs and tissues. Radiofrequency waves are directed at protons in the body. Protons are very abundant in water, and an MR image shows difference in water content in various body tissues. Signals are emitted from these protons to form a very detailed image. MRI is the most sensitive exam for spinal and joint problems because it can give such a clear picture of soft-tissue structures near and around bone. Organs of the abdomen and pelvis, including the liver, kidney, spleen, pancreas, abdominal vessels, reproductive organs and bladder can also be examined in very high detail.

Express Imaging offers two types of MRI scanners: an Open unit and a Hi-field unit. The Open unit is a large machine that is open on all four sides. This unit is great for patients who are claustrophobic or larger in size. The Hi-field unit is cylinder-shaped and open on both ends.

How should I prepare for the procedure?
You should wear comfortable, loose fitting clothing for your MRI exam. Any metal objects will not be permitted into the exam room, so avoid clothing with zippers or snaps. You may be asked to remove hairpins, jewelry, eyeglasses, hearing aids or any removable dental work. Because the strong magnetic field used for MRI will pull on any metal object implanted in the body, you will be given a screening form that will ask a series of questions. Some of these questions may include whether you have a prosthetic hip, pacemaker, port, catheter or any metal plates, pins, screws or surgical staples in your body. In most cases surgical staples, plates, pins and screws pose no risk during an MRI if they have been in place for at least 6 to 8 weeks. You will be asked if you have ever had a bullet or shrapnel in your body or ever worked with metal. If there is any question of metal fragments, you may be asked to have an x-ray to detect any such metal objects. The technologist will go over these and any other questions you might have before you enter the scan room. Women should inform their doctor or technologist if there is any possibility of pregnancy. You can expect most MRI scans to take one hour per area scanned.

What will I experience during an MRI scan?
The patient is placed on a sliding table and positioned comfortably for the MRI examination. Depending on how many images are needed, the exam will generally take 45 minutes, although a very detailed study might take longer. Depending on the part of the body being examined, a contrast material might be injected to enhance the visibility of certain tissues or blood vessels. You will be required to hold very still during the actual imaging process, but between sequences some movement is allowed. You will hear tapping and knocking noises during your exam. The technologist will communicate with you between sets of pictures, and you will also be able to communicate with the technologist. A visitor may accompany you for the MRI scan as long as they also pass the screening process. MRI exams are painless, but some patients find it difficult to remain still during the examination.

Last updated January 22, 2008