Magnetic resonance is a phenomenon in quantum mechanics that affects a magnetic dipole when placed in a uniform static magnetic field. Its energy is split into a finite number of energy levels, depending on the value of quantum number of angular momentum. Magnetic resonance imaging (MRI) uses the body's natural magnetic properties to produce detailed images from any part of the body. ... When the body is placed in a strong magnetic field, such as an MRI scanner, the protons' axes all lineup.