THE 100 MOST INFLUENTIAL INVENTORS OF ALL TIME

7 The 100 Most Influential Inventors of All Time 7

diseases and follow up after treatments. More than 60
million MRI procedures were performed in 2002 alone,
according to the Nobel Assembly.

Paul Lauterbur

Paul Christian Lauterbur received a Ph.D. in chemistry
from the University of Pittsburgh in 1962. He served as a
professor at the University of New York at Stony Brook
from 1969 to 1985, when he accepted the position of pro-
fessor at the University of Illinois at Urbana-Champaign
and director of its Biomedical Magnetic Resonance
Laboratory.
Lauterbur began work in the early 1970s, when the
technology underpinning MRI was a laboratory research
tool. Called nuclear magnetic resonance (NMR) spectros-
copy, it involves putting a sample to be analyzed in a strong
magnetic field and then irradiating it with weak radio
waves at the appropriate frequency. In the presence of the
magnetic field, the nuclei of certain atoms—for example,
ordinary hydrogen—absorb the radio energy; i.e., they
show resonance at that particular frequency. Because the
resonance frequency depends on the kind of nuclei and is
influenced by the presence of nearby atoms, absorption
measurements (absorption signal spectra) can provide
information about the molecular structure of various solids
and liquids. When the nuclei return to their previous
energy levels, they emit energy, which carries additional
information. NMR spectroscopy has remained a key tool
in chemical analysis.
When studying molecules with NMR, chemists always
had tried to maintain a steady magnetic field because
variations made the absorption signals fuzzy. Lauterbur
realized that if the magnetic field was deliberately made
nonuniform, information contained in the signal