An MRI scan is a diagnostic imaging study that allows your physician to look inside your body without the use of radiation, x-rays or surgery. The MRI uses magnetism and radio waves to produce pictures of your head, spine and other parts of your body. These images are used to distinguish normal, healthy soft tissue from unhealthy, pathological tissue. Depending on what information your doctor needs, the MRI scan may require the use of a contrast agent given intravenously to assist in visualizing certain structures in your body. The system produces a knocking sound which represents that the exam is proceeding as required.