MRI (magnetic resonance imaging)
MRI uses radio waves and a strong magnetic field to provide clear and detailed images of internal organs and tissues. We use MRI to diagnose a range of conditions in all parts of the body. MRI provides very detailed pictures of the brain and associated blood vessels. A MRI plays a valuable role in diagnosing disorders of the nervous system.
Because MRI can give such clear pictures of soft tissue, it is often used for examination of major joints and the spine. It is widely used to diagnose sports-related injuries, as well as work-related disorders. The images can allow physicians to see even minute tears or injuries to tendons, ligaments and muscles, as well as degenerative disorders such as arthritis, in a fast, noninvasive way.
Saint Mary's Imaging features the Magnetom Avanto MRI. This 8-channel MRI system with TIM (total image management) provides very high resolution images and is faster, quieter and more comfortable than previous MRI machines.
Preparing for an MRI exam
Because the strong magnetic field used for MRI will pull on any ferromagnetic metal object in the body, MRI staff will ask whether you have a prosthetic hip, an aneurysm clip, pacemaker, port, stent, IUD or any other metal part in your body. In most cases, clips and staples pose no risk during MRI if they have been in place for more than 4 - 6 weeks. Pacemakers cannot be scanned. Dyes used in tattoos can contain metallic iron oxide and could heat up during MRI, however this is rare. If there is any question, you may be asked to have an x-ray that will detect any metal objects. Tooth fillings may distort the facial images. You will be asked to remove anything that might degrade MRI images of the head, including hairpins, jewelry, eyeglasses, hearing aids and any removable dental work. The radiologist may ask if you have any drug allergies and whether you have undergone any surgery in the past. If you are or might be pregnant, mention it to the MRI staff. Some patients who undergo MRI in an enclosed unit may feel confined or claustrophobic. If you are claustrophobic and not easily reassured, please notify us when scheduling your exam and a sedative may be administered.
What does the MRI look like?
The conventional MRI unit is a closed cylindrical magnet in which the patient must lie totally still for several minutes at a time.
How the procedure works
MRI is a unique imaging method that does not use radiation. Instead, radio waves are directed at protons, the nuclei of hydrogen atoms, in a strong magnetic field. The protons are at first "excited" and then "relaxed", emitting radio signals, which can be computer-processed to form an image. In the body, protons are most abundant in the hydrogen atoms of water so that the MRI shows differences in water content and distribution in various body tissues.
How the MRI is performed
The patient is comfortably positioned on a special table, which slides into the MRI system opening where the magnetic field is created. As the individual MRI sequences are performed, the patient will hear tapping noises. The patient is able to communicate with the technologist at any time using an intercom. Depending on how many images are needed the exam can take from 15 to 45 minutes, although some exams may take longer. You will be asked not to move during the actual imaging process, but between sequences some movement is allowed. Patients are generally required to remain still for only a few minutes at a time. Depending on the part of the body being examined, a contrast agent may be given intravenously to enhance the visibility of certain tissues or blood vessels. When the exam is over the patient is asked to wait until the images are examined to determine whether more images are needed.
Exam interpretation
A radiologist will analyze the images and send a signed report with his or her interpretation to your physician, who will inform you of the results.
