Abstract
Computed Tomography (CT) is widely used in diagnostic radiology and radiation therapy. Since the discovery of X-rays in 1895 by William Conrad Roentgen, it was used in diagnostic radiology based on the different attenuation properties of different tissue types. The need of making more accurate diagnosis using 3-dimentional images, CT was developed by Godfrey Newbold Hounsfield and Allan Macleod Cormack in 1979. By reviewing the journey of CT development, we have a better understanding how physics applied in a medical device development. The most advance CT (photon counting CT) and its future potential research and development will be briefly discussed.