Atomic nuclei that contain the same number of protons, but differ in the number of neutrons in the nucleus of the atom for the element concerned. For example, 1H, 2H, and 3H are the three isotopes of hydrogen, otherwise known as proton, deuterium, and tritium. Various isotopes have different nuclear magnetic moments and different resonant frequencies. Many isotopes have no magnetic moment and are therefore not observable by MR.

See also Isomer.

Equal intensity in all directions.

Motion, which is uniform in all directions. This is generally used in reference to molecular diffusion or rotation, which gives rise to relaxation of the spin system through the dipole dipole interaction.

A voxel that is uniform in all directions.