After they got married, Cormack returned to lecture at the University of Cape Town in early 1950. After he took a break at Harvard from 1956 to 1957, Cormack and Seavey moved to the United States. He would then take a job as a professor at Tufts University in 1957. In 1966, he became a naturalized citizen of the United States. Even though he was mostly working on particle physics, he had a side interest in x-ray technology which led him to develop the theoretical underpinnings of CT scanning. The work that he did on this started at the University of Cape Town and Groote Schuur Hospital in early 1956. It continued shortly in mid-1957 after he returned from his break. His results were afterwards published in two papers in the Journal of Applied Physics in 1963 and 1964. The papers that had been published drew hardly any interest until the first CT scanner was built by Hounsfield and colleagues in 1971 which took Cormack's theoretical calculations into a real application. He was then the recipient of the 1979 Nobel Prize in Physiology or Medicine which he shared with Godfrey Hounsfield. In 1990, he was awarded the National Medal of Science.