Milestone-Proposal:The Birth of the First CT Scanner

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Docket #:2020-02

This Proposal has been approved, and is now a Milestone

To the proposer’s knowledge, is this achievement subject to litigation? No

Is the achievement you are proposing more than 25 years old? Yes

Is the achievement you are proposing within IEEE’s designated fields as defined by IEEE Bylaw I-104.11, namely: Engineering, Computer Sciences and Information Technology, Physical Sciences, Biological and Medical Sciences, Mathematics, Technical Communications, Education, Management, and Law and Policy. Yes

Did the achievement provide a meaningful benefit for humanity? Yes

Was it of at least regional importance? Yes

Has an IEEE Organizational Unit agreed to pay for the milestone plaque(s)? Yes

Has the IEEE Section(s) in which the plaque(s) will be located agreed to arrange the dedication ceremony? Yes

Has the IEEE Section in which the milestone is located agreed to take responsibility for the plaque after it is dedicated? Yes

Has the owner of the site agreed to have it designated as an IEEE Milestone? Yes

Year or range of years in which the achievement occurred:


Title of the proposed milestone:

First Computerized Tomography (CT) X-ray Scanner, 1971

Plaque citation summarizing the achievement and its significance:

On 1 October 1971, a team at the EMI Research Laboratories located on this site produced an image of a patient’s brain, using the world’s first clinical X-ray computerized tomography scanner, based on the patented inventions of Godfrey Hounsfield. The practical realization of high-resolution X-ray images of internal structures of the human body marked the beginning of a new era in clinical medicine.

Justification for including Godfrey Hounsfield's name in the Citation:

The achievement being commemorated by the plaque is in respect of first human tissue image by a practical and reproducible CT scanner designed by Godfrey Hounsfield and built by EMI. Hounsfield's fundamental role was recognised by the award of the two US patents in his name, #3778614 and #4052619 cited below, as well as by a Nobel Prize. The patents were tested in the US courts and upheld.

Whilst the Nobel prize was shared with Alan Cormack, Cormack worked independently in the United States and played no part in the EMI Labs achievement.

200-250 word abstract describing the significance of the technical achievement being proposed, the person(s) involved, historical context, humanitarian and social impact, as well as any possible controversies the advocate might need to review.

IEEE technical societies and technical councils within whose fields of interest the Milestone proposal resides.

In what IEEE section(s) does it reside?

United Kingdom and Ireland

IEEE Organizational Unit(s) which have agreed to sponsor the Milestone:

IEEE Organizational Unit(s) paying for milestone plaque(s):

Unit: United Kingdom and Ireland
Senior Officer Name: Dr Mona Ghassemian

IEEE Organizational Unit(s) arranging the dedication ceremony:

Unit: United Kingdom and Ireland Section
Senior Officer Name: Dr Mona Ghassemian

IEEE section(s) monitoring the plaque(s):

IEEE Section: United Kingdom and Ireland
IEEE Section Chair name: Dr Mona Ghassemian

Milestone proposer(s):

Proposer name: Charles W Turner
Proposer email: Proposer's email masked to public

Please note: your email address and contact information will be masked on the website for privacy reasons. Only IEEE History Center Staff will be able to view the email address.

Street address(es) and GPS coordinates in decimal form of the intended milestone plaque site(s):

150 Clayton Road Hayes Middlesex England GPS: 51.50556, -0.42659

Describe briefly the intended site(s) of the milestone plaque(s). The intended site(s) must have a direct connection with the achievement (e.g. where developed, invented, tested, demonstrated, installed, or operated, etc.). A museum where a device or example of the technology is displayed, or the university where the inventor studied, are not, in themselves, sufficient connection for a milestone plaque.

Please give the address(es) of the plaque site(s) (GPS coordinates if you have them). Also please give the details of the mounting, i.e. on the outside of the building, in the ground floor entrance hall, on a plinth on the grounds, etc. If visitors to the plaque site will need to go through security, or make an appointment, please give the contact information visitors will need. Jupiter House, former EMI Head Office

Are the original buildings extant?


Details of the plaque mounting:

Exterior wall of Jupiter House

How is the site protected/secured, and in what ways is it accessible to the public?

Plaque will be permanently fixed to the wall.

Who is the present owner of the site(s)?

The Home Group, 2 Gosforth Park Way, Newcastle-on-Tyne, England

What is the historical significance of the work (its technological, scientific, or social importance)? If personal names are included in citation, include justification here. (see section 6 of Milestone Guidelines)

The EMI CT Scanner was the first machine that used computerized tomography to produce X-Ray images of the internal organs of the human body, for example the brain.

The evolution of the first practical implementation of computer-assisted tomography culminated in the X-ray scanner invented and developed by EMI Electronics on this site within its Hayes, Middlesex campus in 1970. This was the World’s first medical imaging system capable of producing high resolution detailed scans of internal body structures, such as the brain, heart, and other organs.

The mathematical basis of tomography has a long history, dating back to the early 20th century, but it was not until the advent of modern high speed computers capable of processing large data sets (such as those used in medical imaging applications) within practical time scales, that high resolution images could be obtained. Oldendorf (1963) is acknowledged to be the first to conceptualise the possibility of extracting useful data from line integrals. The work of Allan Cormack (1963) posed the question of whether it might be possible to deduce the internal structure of a solid object using external measurements under laboratory conditions. This was essentially the challenge that the EMI team set themselves to accomplish, building on the theoretical work of groups in Europe and the United States over several decades.

The work of Johann Radon (1986) and Stefan Kaczmarz (1993) had established the basic framework within which a successful imaging system could be achieved. The concept of tomographic imaging derives from the solution to the problem of reconstructing the set of values of a physical quantity along a defined path, using the data obtained from the multiple transmission of a beam of energy (e.g. light, acoustic waves, radio waves, or X-rays) through the object under investigation. The outcomes of a set of transmission measurements obtained from numerous scans performed over a 360 degree range of angles in a defined plane (or slice) form the data set from which the physical properties of the medium being investigated can be evaluated. Manipulating the data to yield accurate solutions quickly depended upon two fundamental breakthroughs. Kaczmarz (1003) demonstrated how to improve the efficiency of obtaining the solution of a large system of linear equations. Radon’s contribution was to devise the Radon Transform that became an important technique in signal processing applications. In this way, the image of a 3-dimensional opaque object can be obtained. The image is assembled slice by slice (hence the use of the word tomography, derived from the Greek word tomos, meaning ‘slice’). The resolution of the image determines the size of the data set. In clinical practice, for example, the production of a complete set of images requires the performance of a processing system that was well beyond the capability of laboratory computers, until the advent of the first mini-computers in the 1960/70s.

It was a team led by Godfrey (later Sir Godfrey) Hounsfield that began work in 1967 with the aim of applying the principles of tomography to an imaging system employing X-rays. The challenge was to produce a device that could be used safely in clinical practice. This imposed strict limits on the transmitted intensity of the X-ray beam used and the sensitivity of the receiving detection system. The first working prototype was built at EMI’s laboratories ay Hayes in 1971 and was used for brain-scanning at Atkinson-Morley Hospital in Wimbledon, London, that year. The significance of this invention to the field of medical imaging, especially of the human brain, was quickly recognised. Groups across the world began work on various developments of the original concept, as the application of computer-assisted tomography became commercially viable. The modern versions of the CT scanner, as it has become known, are installed in innumerable hospitals across the developed world, where it is used routinely for whole body, or part body, imaging of patients. The impact on clinical medicine has been immense. The technology has developed to the point where whole body scans can be completed now in less than 1 second. The EMI team achieved world –wide recognition for the 1967 invention and were granted numerous patents, some of which are referred to below. Godfrey Hounsfield received the Nobel Prize in Medicine in 1979. The Prize was awarded jointly to Allan Cormack of Tuft’s University, USA, in recognition of his seminal contributions to establishing the theoretical basis of tomography, although his ideas were not reduced to practice before Hounsfield’s team demonstrated that a feasible imaging methodology could be based on this concept.

What obstacles (technical, political, geographic) needed to be overcome?

The scanning procedure required the acquisition of very large sets of data obtained by precision rotation of the X-Ray source and detector combination. The complete scan had to be accomplished within a practicable time frame. The incident X-Ray intensity had to be limited to safe levels for clinical applications.

What features set this work apart from similar achievements?

The EMI CT Scanner was the first clinical machine capable of producing high resolution images of X-ray attenuation, allowing depiction of the internal structures and organs of the human body.

Supporting texts and citations to establish the dates, location, and importance of the achievement: Minimum of five (5), but as many as needed to support the milestone, such as patents, contemporary newspaper articles, journal articles, or chapters in scholarly books. 'Scholarly' is defined as peer-reviewed, with references, and published. You must supply the texts or excerpts themselves, not just the references. At least one of the references must be from a scholarly book or journal article. All supporting materials must be in English, or accompanied by an English translation.

Details of the supporting texts and other reference materials are provided separately via a number of attached files. Also attached are the permissions from the site owner and the UK & Ireland Section Chair

Supporting materials (supported formats: GIF, JPEG, PNG, PDF, DOC): All supporting materials must be in English, or if not in English, accompanied by an English translation. You must supply the texts or excerpts themselves, not just the references. For documents that are copyright-encumbered, or which you do not have rights to post, email the documents themselves to Please see the Milestone Program Guidelines for more information.

Hounsfield, G.N., "Computerized transverse axial scanning (tomography), Part I. Description of a system", British Journal of Radiology, 46, 1016-1022, 1973

Strong, A.B., Hurst, R.A.A., "Correspondence: EM1 patents on computed tomography: history of legal actions", The British Journal of Radiology, 67, 315-317, 1994

Yang, Guang-Zhong and Firmin, David N. "Retrospectroscope: The Birth of the First CT Scanner", IEEE Engineering in Medicine and Biology, January/February 2000

Please email a jpeg or PDF a letter in English, or with English translation, from the site owner(s) giving permission to place IEEE milestone plaque on the property, and a letter (or forwarded email) from the appropriate Section Chair supporting the Milestone application to with the subject line "Attention: Milestone Administrator." Note that there are multiple texts of the letter depending on whether an IEEE organizational unit other than the section will be paying for the plaque(s).

Please recommend reviewers by emailing their names and email addresses to Please include the docket number and brief title of your proposal in the subject line of all emails.