What makes the hydrogen atom important for MRI?
Hydrogen atoms and other atoms with an odd number or protons and neutrons possess a specific quantum property called spin angular momentum. Spin is where an atom rotates about its own axis and because atoms are charged particles they create small magnetic fields. The atoms are able to occupy multiple different states of spin, but are normally randomly distributed between them. However, in the presence of an external magnetic field the atoms will align their spin states either with or against the external magnetic field depending on whether it is in a low or high energy state. This phenomenon results in giving the object inside the magnetic field a very weak magnetic charge described by what is known as the net magnetization vector (NMV).
