Radio Waves Decoded

Once the protons are aligned, the MRI fires a pulse of radio waves at exactly the right frequency to knock them out of alignment — like flicking a row of standing dominoes.

When the radio pulse stops, the protons gradually realign with the magnetic field. As they return, they emit faint radio signals. Different tissues realign at different speeds — fat protons snap back quickly, water protons take longer. That timing difference creates contrast.