The nuclear spin, which is the fundamental atomic attribute underlying the magnetic resonance imaging, is an exact two-state quantum system. Therefore, it is a suitable candidate to be used as a qubit in quantum computing. The aim of this letter is to review the main equations governing the dynamics of the spin magnetic dipole moment in Magnetic Resonance Imaging. It is also shown that exposing the magnetic dipole moment to a continuous-wave B1-field results in travelling back and forth between its two energy states. It absorbs energy from the background radiation when going from the lower to the higher energy state, and injects the same amount of energy back into its surroundings when relaxing from the higher to the lower energy state. In a complete cycle, the dipole moment behaves therefor purely reactive with zero net energy exchange with its environment.
