Spatial Resolution in Magnetic Resonance Imaging

In 1973, Dr. Paul C. Lauterbur published his seminal article on using magnetic field gradients to resolve the sources of nuclear magnetic resonance (NMR) signals into pixels or voxels.¹ Most physicists at the time believed this to be impossible, due to the general principle that spatial resolution is limited by the wavelength of the electromagnetic radiation used as a probe. At a magnetic field strength of 1 Tesla, the wavelength of electromagnetic radiation that excites hydrogen nuclei is 7 meters (3 × 10⁸ meters/second/(42.6 × 10⁶ 1/seconds) = 7.04 meters), which would make studying details in the human body impossible. Lauterbur correctly recognized and demonstrated that this limitation, while applying to scattering experiments, was cleverly overcome by using magnetic field gradients to localize signals in NMR. He called his new technique “zeugmatography”. Until the early 1980s, most researchers favored the name “NMR imaging”. The “nuclear” in NMR imaging was dropped when whole-body scanners became clinically available in the early 1980s. This was done to avoid adverse reactions from the public about potential association with “nuclear” imaging and its associated radiation effects. Paul Lauterbur shared the 2003 Nobel Prize in medicine for his invention of MRI.