MRI stands for Magnetic Response Imaging. Hydrogen atoms in the body are realigned by magnetic fields and radio waves, producing very faint signals. Those signals are then used to create images that can examine details of organs, tissues, and the skeletal system. The machine is just a large tube with two open ends. The patient lies on a table that slides into the machine. Depending on the need for the MRI, either a limb or the whole body will be in moved into the machine.