How does MRI work?
First, patients go into a narrow tube which is surrounded by a strong magnet. Then, the magnet turns on, so hydrogen atoms line up in the direction of the magnetic field. Next, radio pulses are applied to the body area under examination. Atoms in the area absorb some of its energy, so they spin with a certain direction and frequency. Then, small magnets are switched on and off to activate regions called slices. After that, the radio pulse turns off, and the hydrogen atoms release their absorbed energy, which shows a signal the MRI machine detects in the brain. Finally, a computer deciphers the signals, and uses them to build a picture of the slice.