Magnetic resonance imaging (MRI) is a technique that uses a magnetic field and radio waves to create detailed images of the body. MRI machines are large, tube-shaped magnets. The magnetic field temporarily realigns hydrogen atoms in your body. Radio waves cause these aligned atoms to produce very faint signals, which are used to create MRI images. The MRI machine can also be used to produce 3-D images that may be viewed from many different angles. This is a noninvasive way to examine organs, tissues and skeletal system with high-resolution images and help diagnose a variety of problems.
A functional MRI of the brain (fMRI) measures the metabolic changes that occur within the brain. It may be used to examine the brain's anatomy and determine which parts of the brain are handling critical functions. This helps identify important language and movement control areas in the brains of people being considered for brain surgery. Functional MRI may also be used to assess damage from a head injury or from disorders such as Alzheimer's disease.
Another MRI procedure may be used in addition to mammography to detect breast cancer, particularly in women who have dense breast tissue or who may be at high risk of the disease.