In June 1973, the first computed tomography (CT) scanner in the U.S. was installed at the Mayo Clinic in Rochester, MN. By the end of 1974, 44 similar systems had been installed at medical facilities around the country.

At the time, CT imaging was limited to head studies, but with the introduction of contrast agents and full body CT systems the changes in the practice of medicine became even more significant. CT imaging was hailed by the US medical community as the greatest advance in radiology since the discovery of x-rays. than 4 years after the introduction of CT imaging in the US, at least 400 CT systems had been installed.