In magnetic resonance a sample is placed in a magnetic field and then subjected to radio waves. The nuclei in the sample absorb the radio waves and then re-emit them at a frequency that depends on the magnetic moment of the nucleus and the strength of the magnetic field. By measuring these waves it is possible to learn more about the chemical structure of the sample.

In 1973 Lauterbur, then at the State University of New York at Stony Brook, discovered that it was possible to make two-dimensional images of the sample by adding a gradient to the magnetic field. Mansfield then showed how the so-called echo-planar technique could be used to greatly increase the image acquisition rate, making medical applications practical. Most medical applications of MRI rely on imaging the hydrogen atoms in water molecules.

Mansfield was born in 1933 and received his BSc from Queen Mary College in London in 1959, followed by a PhD in 1962. After two years at the University of Illinois he moved to the physics department at Nottingham, where he has been based ever since. Mansfield is a fellow of the Royal Society and an honorary fellow of the Institute of Physics, and was knighted in 1993.

Lauterbur as born in Sidney, Ohio, in 1929 and graduated in chemistry from the Case Institute of Technology in Cleveland in 1951. He received his PhD from the University of Pittsburgh, and moved from Stony Brook to Illinois in 1985.

The magnetic properties of nuclei – the basis of MRI – were first measured by Isidor Rabi in the 1930s, while Felix Bloch and Edward Purcell independently discovered nuclear magnetic resonance in 1946. All three received the Nobel Prize for Physics for their discoveries: Rabi in 1944 and Bloch and Purcell in 1952.