What is an MRI/MRA?
MRI (Magnetic Resonance Imaging) and MRA (Magnetic Resonance Angiogram) are a procedure practiced for the diagnosis of conditions using radiofrequency waves and a strong magnetic field rather than radiation, the machine sends signals to a computer that makes a series of images. Each image will show a thin slice of your body. The computer compiles these slices into a 3-D picture. The primary difference between the two methods is an MRA is specifically used for examining blood vessels and an MRI is focused on gathering essential information about your spine, joints, brain and other internal organs. They can study your muscles, nerves, bones, ligaments and other tissues using images from this procedure. This test requires specialized equipment and expertise and allows evaluation of some bodies structures that may not be as visible with other imaging methods. The procedure is safe, painless and because of the superior clarity of the images it allows for early detection and treatment of disease without invasive procedures such as surgery.
How should I prepare for the procedure?
There is no special preparation for an MRI procedure. Clothes most be metal-free, otherwise we will provide you a gown. Watches, hearing aids, hair clips, bank cards, keys, cell phones, and other metal objects will not be allowed in the scan room. You will be asked to remove anything that might degrade MRI images of the head, including hairpins, jewelry, eyeglasses, hearing aids, piercing and any removable dental work. Because the strong magnetic field used for MRI will pull on any ferromagnetic metal object implanted in the body, MRI staff will ask whether you have a prosthetic hip, heart pacemaker (or artificial heart valve), implanted port, infusion catheter (brand names Port-o-cath, Infusaport, Lifeport), intrauterine device (IUD), 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 MRI if they have been in place for more than four to six weeks. Tattoos and permanent eyeliner may also create a problem. 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 that will detect any such metal objects. Tooth fillings usually are not affected by the magnetic field but they may distort images of the facial area or brain, so the radiologist should be aware of them. The same is true of braces, which may make it hard to “tune” the MRI unit to your body.
The radiologist or technologist may ask about drug allergies and whether head surgery has been done in the past. If you might be pregnant, this should be mentioned. Some patients who undergo MRI in an enclosed unit may feel confined or claustrophobic. If you are not easily reassured, a sedative may be administered. Roughly one in 20 patients will require medication to reduce the anxiety associated with claustrophobia.
What will I experience during the MRI procedure?
MRI causes no pain but some patients can find it uncomfortable to remain still during the examination. Others experience a sense of being “closed in,” though the more open construction of newer MRI systems has done much to reduce that reaction. The technologist will direct the scan from the computer console. You will hear a light tapping or knocking sounds and the scan will consist of several sets of images with brief pauses in-between. You may notice a warm feeling in the area under examination; this is normal but if it bothers you the radiologist or technologist should be notified.
If a contrast injection is needed, there may be discomfort at the injection site and you may have a cool sensation at the site during the injection. Most bothersome to many patients are the loud tapping or knocking noises heard at certain phases of imaging. Ear plugs are provided to minimize the clamor.
Who interprets the results and how do I get them?