MRI scanning. Patient undergoing a magnetic resonance imaging (MRI) scan of their head. The resulting images are displayed on the computer screen at left. MRI scanning uses strong magnetic fields to produce radio emissions from hydrogen atoms in the body. It is used to produce cross- sectional body images, and is most useful for imaging soft tissues such as the brain. This is the Polestar N20 intraoperative MRI machine. It can be used to produce images of a patient's brain before, during and after neurosurgery.