An MRI (or magnetic resonance imaging) scan is a radiology technique which uses magnetism, radio waves, and a computer to produce images of body structures. The MRI scanner is a tube surrounded by a giant circular magnet. The patient is placed on a moveable bed which is inserted into the magnet. The magnet creates a strong magnetic field which aligns the protons of hydrogen atoms, which are then exposed to a beam of radio waves. This spins the various protons of the body, and they produce a faint signal which is detected by the receiver portion of the MRI scanner. The receiver information is processed by a computer, and an image is then produced.
The image and resolution produced by MRI is quite detailed and can detect tiny changes of structures within the body. For some procedures, contrast agents such as gadolinium are used to increase the accuracy of the images.