What is MRI?
MRI stands for magnetic resonance imaging. Using machines like the scanner in this picture, doctors and researchers use powerful magnets and radio waves to get clear pictures of what is going on inside of your body or inside of your brain, without x-rays. Worldwide more than 60 million MRI exams take place each year.
How does MRI work?
MRI works because the human body is mostly water. This means you have lots of hydrogen atoms spinning around inside of you. Inside the MRI scanner, imagine a giant magnet that pulls all of those hydrogen atoms to point in the same direction, so that they line up, like microscopic compass needles. When the the magnetic field is relaxed, the hydrogen atoms also "relax" and return to their randomly spinning state. As the hydrogen atoms relax, they release a signal that can be detected by the scanner. According to the kind of tissue the water molecules are in, they relax at different rates. Coils placed around the body capture the signals in hundreds of cross-sectional pictures likes the slices in a loaf of bread. These pictures are assembled by a powerful computer to produce three dimensional images of remarkable clarity.
Unlike ordinary x-rays of computed tomography (CT) scans, MRI does not expose the body to X-radiation. Another advantage over CT is that MRI provides greater contrast between different tissues of the body. MRI can be used to learn about tumors and problems in organs, blood vessels, joints, and bones, as well as about normal, healthy growth and development.
What's going on in your head?
Just think, doctors and researchers can see your brain in action. By watching changes in blood flow in your brain, researchers can view what happens in the brain when you think, talk, move or feel. Functional MRI (fMRI) provides clear pictures of brain function that would remain hidden by other imaging technology. MRI is a powerful tool for planning surgery, and has also opened the frontier to "brain mapping" and better understanding and treating medical conditions, such as depression
Any reason to avoid MRI?
MRI is safe and effective for most people. However, people that have claustrophobia, metal implants, or braces, should avoid MRI. Also the machine is very loud, so ear protection is a must. Some people wonder about MRI during pregnancy. There are MRI scans that are designed specifically for pregnancy, and large numbers of women participate in MRI for medical reasons every day. Prenatal MRI research is becoming increasingly common, in part, because there are no known safety concerns. Nonetheless, we advise pregnant women to ask questions and feel comfortable before choosing to participate.
Magnetic resonance imaging (MRI) machines are a technological marvel. Here are some basic facts about how they work and how we use them in research.