When someone suffers from an internal ailment that cannot be detected by a traditional office examination, an MRI may be necessary. When an MRI is administered, the patient lies on a retractable platform which enters the center of the machine. Upon entering the machine, the patient is scanned by one of several magnetic coils that emit a radio frequency pulse targeted at the specific region to be examined. This creates a magnetic field that runs down the center of the tube. There are billions of hydrogen atoms within the body, which rotate on a natural axis. When the magnetic current is introduced, the atoms align to it like a compass and spin on a new axis. When the magnetic force is removed, the atoms return to their natural alignment. As they relax, they emit energy and act as a small radio transmitter. Different tissues release different energy levels and the computer recognizes their distinct pulses. The difference in energy is determined by the atoms' realignment time. Dense tissue takes longer to realign than soft tissue. So, when the computer receives the different energy levels it creates an image, which shows dense areas as white and less dense areas as black. With this procedure the MRI can show, organs, tendons, ligaments, etc. It is only because of the sheer number of hydrogen atoms in your body that MRI technology is possible.