History of CT scan in Timeline

A computed tomography (CT) scan is a medical imaging technique providing detailed internal body images. It utilizes a rotating X-ray tube and detectors to measure X-ray attenuation by tissues. Radiographers or radiology technologists operate the equipment. Data acquired from various angles is processed using computer algorithms to create cross-sectional images. CT scans are applicable even with metallic implants or pacemakers, where MRI is unsuitable.

1917: Radon Transform Mathematical Theory

The history of X-ray computed tomography goes back to at least 1917 with the mathematical theory of the Radon transform.

October 1963: Oldendorf Receives Patent for Radiant Energy Apparatus

In October 1963, William H. Oldendorf received a U.S. patent for a "radiant energy apparatus for investigating selected areas of interior objects obscured by dense material."

1972: First Commercially Viable CT Scanner Invented

In 1972, Godfrey Hounsfield invented the first commercially viable CT scanner.

1975: Introduction of the Term Sinogram

In 1975, the term sinogram was introduced by Paul Edholm and Bertil Jacobson.

1977: Computed Axial Tomography in Medical Subject Headings

From 1977 to 1979, computed axial tomography was used in Medical Subject Headings (MeSH).

1979: Computed Axial Tomography in Medical Subject Headings

From 1977 to 1979, computed axial tomography was used in Medical Subject Headings (MeSH).

1979: Nobel Prize Awarded for CT Development

In 1979, Allan MacLeod Cormack and Godfrey Hounsfield were jointly awarded the Nobel Prize in Physiology or Medicine for their development of computer-assisted tomography.

1980: Increase in CT Scans for Children

As of 1980, six to eleven percent of CT scans are done in children, an increase of seven to eightfold.

1998: CT or MRI Imaging in Emergency Departments

In the emergency department in the United States, CT or MRI imaging is done in 15% of people who present with injuries as of 2007 (up from 6% in 1998).

2007: Proportion of Unnecessary CT Scans

As of 2007, a proportion of CT scans are performed unnecessarily in the United States, with some estimates placing this number at 30%.

2007: Medical Imaging's Contribution to Radiation Exposure

As of 2007, medical imaging accounted for half of the radiation exposure of those in the United States, with CT scans making up two thirds of this amount. Globally, the average radiation dose from medical sources was approximately 0.6 mSv per person in 2007.

2007: CT Scan Manufacturers Offer Lower Exposure Function

As of 2007, most manufacturers of CT scans have a function built in for lower exposure in children.

2007: Estimated CT Scans Performed in US

In 2007, an estimated 72 million CT scans were performed in the United States, accounting for close to half of the total per-capita dose rate from radiologic and nuclear medicine procedures.

2007: Estimated 72 Million CT Scans Performed in the US

In 2007, an estimated 72 million CT scans were performed in the United States, reflecting a significant increase in CT scan usage over the preceding two decades.

2007: Estimated Cancer Cases from CT Scans

One study estimated that as many as 0.4% of cancers in the United States resulted from CT scans, and that this may have increased to as much as 1.5 to 2% based on the rate of CT use in 2007.

2009: FDA Investigation of Brain Perfusion CT Scans

In October 2009, the US Food and Drug Administration (FDA) initiated an investigation of brain perfusion CT (PCT) scans due to radiation burns caused by incorrect settings at a facility.

2012: Review on Medical Radiation and Cancer Risk in Children

A 2012 review did not find an association between medical radiation and cancer risk in children, noting limitations in the evidences the review is based on.

2015: Over 80 Million CT Scans Performed in the US

In 2015, the number of CT scans performed in the United States exceeded 80 million, continuing the upward trend in CT scan utilization.

February 2016: Photon Counting CT in Use at Three Sites

As of February 2016, photon counting CT is in use at three sites. This technology is under development and has potential advantages, including improving signal to noise ratios and reducing doses.