MRI MRI is a computer-based cross sectional imaging modality. However the principles are different from CT and X-rays in that no ionizing radiation is employed during the examination. Instead, MRI creates images of structures through the interaction of magnetic fields and radio waves with tissues. Prior to the examination, patients must complete a screening questionnaire to identify any potential risks or contraindications before entering the magnetic environment. Once cleared to enter the exam room, the procedure takes about 30 minutes. Patients can help to produce high quality images by lying still throughout the exam, during which dozens of images will be created. When scheduling your MRI appointment, please let us know if you have any of the following: Cardiac pacemaker Any internal electronic device Artificial heart valve or stents Medical surgical clips or aneurysm clips Intrauterine device Hearing aid or implant Shunts Neurostimulators Artificial joints/metal rods Embedded shrapnel or metal fragments Learn more about the tests.