Timeline

1917	Johann Radon demonstrated that the image of a 3-dimensional object can be recostructed from an infinite number of 2-dimsneisonal projections of the object
1956	Ronald Bracewell publishes paper mapping sunspots using a series of one-dimensional images to reconstruct a two-dimensional image using Fourier transform
1958	William Oldendorf builds a model CT scanner without a computer
1960	Oldendorf applies for a patent for his model
1963	Alan Cormack publishes results from experimental scanner using a computer to reconstruct images from data
1966	David Kuhl publishes paper with the transmission images of a subject's thorax
1967	Bracewell reconstructs lunar images without using Fourier transforms
1968	EMI patents Godfrey Hounsfieild's method apparatus and the apparatus for scanning the body with X-rays
1971	The first CT scanner, limited to the head, demonstrated by EMI at Atkinson Morley's hospital in London
1972	The first CT scanner demonstrated in the United States
1973	Robert Ledley markets ACTA, a whole body CT scanner
1975	Second gerneration Delta CT scanners are marketed GEs third generation CT scanners are marketed
1979	Cormack and Hounsfield are awarded the Nobel Prize in Medicine for the invention of CT
1985	Superfast CT is developed by Douglas Boyd
1989	First spiral CT enters the market

Sources

Hendee, W. R. (1989). Cross sectional medical imaging: A history. Radiographics, 9(6), p.1155-1180

Holtzmann Kevles, B. (1998). Naked to the bone: Medical imaging in the twentieth century. Rutgers University Press, New Brunswick, NJ.

Siemens Medical. Computed Tomography: Its History and Technology. Retrieved from http://www.medical.siemens.com/siemens/zh_CN/gg_ct_FBAs/files/brochures/CT_History_and_Technology.pdf