Lauterbur's work in the 1970s showed how it was possible for such images to detail cross sections of different structures. Mansfield showed how differences in magnetic fields could be rapidly transformed into a usable image.
More than 60 million MRIs are performed each year. The imaging process has been especially valuable in examinations of the brain and spinal cords. The Nobel committee said the procedure has reduced risk and discomfort to many patients.
Lauterbur, 74, from the University of Illinois, and Mansfield, 70, from Nottingham, England, will receive the prize -- along with its $1.3 million award -- Dec. 10 in ceremonies in Stockholm.
The Nobel prize in literature was announced last week. The Nobel for physics is scheduled to be announced Tuesday. The recipient of the 2003 Nobel Peace Prize will be announced Friday.