Godfrey Hounsfield

Last revised by Daniel J Bell on 30 Mar 2023

Sir Godfrey N Hounsfield (1919-2004) pioneered the CT scanner making him one of the greats in the history of radiology and medicine in general. For his work, he received the Nobel Prize in Physiology or Medicine in 1979. This was remarkable because he had had no previous experience of working in the medical field but was an engineer who hitherto had spent his career developing computers and radar.

Godfrey Newbold Hounsfield was born 28 August 1919 in Nottinghamshire, UK, the last of five children. Growing up on a small farm near Newark-on-Trent, UK 2, he attended Magnus Grammar School in Newark, where he demonstrated a flair for physics and mathematics 7. Nevertheless he left school at age 16 with no formal qualifications, however he had always demonstrated a keen interest in machinery on his family's farm.

Godfrey volunteered for the Royal Air Force in October 1939, at the start of World War II. He became a radar-mechanic instructor, and was posted to RAF Cranwell with a promotion to Corporal. He achieved his City & Guilds examination in radio communication. After the war ended, Air Vice-Marshal John Cassidy supported Godfrey's application for a grant to study at Faraday House Electrical Engineering College, in London, from which he graduated with a Diploma of Faraday House 7

Godfrey joined the Electric and Musical Industries (EMI) company, where he worked on radar and computers until 1967. He led the design team for the EMIDEC 1100 computer, the UK's first large all-transistor computer which was successfully launched in 1959, mostly using skills which he had taught himself or learnt in the Royal Air Force 1,7

In 1967 Godfrey’s previous projects ceased to be of interest to EMI because of changes in company strategy. He was asked to suggest a new line of work involving pattern recognition, and he suggested what eventually became CT scanning 2.

Hounsfield proposed that by using x-rays one could take multiple exposures around an object to determine its internal structure.

EMI was unenthusiastic because they had no significant medical business, Godfrey had no medical knowledge, and his proposal was a high-risk leap beyond existing technology. So they sought external funding, and Godfrey managed to get a small amount of funding from the UK Government Department of Health and Social Security 3. His struggles for financing continued for the next four years, and he also had to struggle against apathy from most of the medical profession. Visits to radiologists at many leading hospitals found that almost everyone (with the notable exceptions of James Ambrose, Louis Kreel, Evan Lennon and Frank Doyle) thought that his proposal was pointless 2.

James Ambrose, a neuroradiologist at Atkinson Morley Hospital, in London, would go on to assist Hounsfield in the various prototypes of the CT scanner. Initially, the original prototype CT scanner was used to examine brains obtained from a histopathology museum. However, preserved brains were not the ideal candidates for mimicking the living human brain. Bovine brains were sought as a solution to this problem. Unfortunately, the electric shock given to the cows in the abattoir resulted in diffuse cerebral hemorrhage, again not a good model for the living human brain. Finally, the idea to use ‘kosher’ slaughtered cows came into being, with cows killed under strict kosher guidelines not suffering widespread hemorrhage, resulting in the first promising scans of the brain in 1968 2,7.

In 1968 Hounsfield was granted UK Patent No. 1283915 for "A Method of and Apparatus for Examination of a Body by Radiation such as X or Gamma Radiation" for his new scanner and its technology 7.

The first clinical CT scan was conducted on 1 October 1971 at the Atkinson Morley Hospital, demonstrating a well-defined cyst 1-3.

Everything changed after he presented his initial CT scans at conferences in London on April 1972 and New York in May 1972. As soon as people saw these images, they realized the groundbreaking potential of this new technique. He was the first to show discrimination between soft tissues, tumors and blood clots in clinical use at acceptable cost and dose 1

Hounsfield was awarded the Nobel Prize in Physiology or Medicine in 1979. The Nobel was co-awarded to Allan M Cormack, a South African-American physicist who, unbeknownst to Hounsfield had developed the theoretical mathematics underpinning the CT scanner 1-6.

Hounsfield created the Hounsfield unit (HU) a dimensionless quantity used to express a linear transformation of the measured attenuation coefficient in the form of a simple number. In the early years, radiologists would use large paper printouts of Hounsfield units to interpret brain scans 2.

Godfrey thought in an unusual way which he described as “you’ve just got to use the absolute minimum of maths but have a tremendous lot of intuition” 3. This is easy to say, but very hard to get right. He used a lot of pictures and mental models, a lot of analogies, and he had a lot of curiosity about how everything in the world worked. This was uncomfortable for academics. How could this highly mathematical field be opened up by someone who was not a mathematician, and not even an academic, but a man who relied primarily upon intuition? 

Sir Godfrey Hounsfield rarely used his title, preferring just Godfrey. He was gentle, generous, modest and unambitious, but doggedly persistent in his work. He liked working in small teams, but he was always slightly outside the formal structure - a man who set his own rules. Although some people of his seniority rarely talked to those beneath them, he would talk to anybody who was interested in his work, whether it was the cleaner, the panel-beater or the managing director. He was sociable: people who met him would see him as an amiable person who helped to wash up the coffee cups, and he would prefer not to tell them of his past achievements. 

From his teenage years onward he was interested in how things worked, and in how science and engineering could help to improve the world. He wanted to pass this enthusiasm on to the next generation. Although he dreaded public speaking, in February 1983, he agreed to open a new library at his old school, Magnus Grammar School, and speak to the pupils there. He told them that “each new discovery brings with it the seeds of other, future, inventions. There are many discoveries, probably just around the corner, waiting for someone to bring them to life. Could this possibly be you?” 4

Sir Godfrey Hounsfield died on 12 August 2004 in Kingston upon Thames, in southwest London 7.

  • Barclay Prize of the British Institute of Radiology (1974)

  • Fellow of the Royal Society (FRS) (1975)

  • Commander of the Order of the British Empire (CBE) (1976)

  • Nobel Prize in Physiology or Medicine (1979)

  • Knighted (1981)

This article is based, with permission, on a biography 1 which clarifies some misunderstandings. For example, Godfrey joined EMI in 1949 (not 1951), his studies at Faraday House did not reach university level, and the development of CT was not linked to The Beatles.

He worked on CT from first principles, independently of predecessors (including Johann Radon, G Frank, C Tetel’Baum, R Bracewell, W Oldendorf, David Kuhl, and Allan M Cormack). Hounsfield himself stated his personal debt was to others: a physics teacher called Mr Ashton, the RAF and John Cassidy, and Alan Blumlein.

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Cases and figures

  • Figure 1: Godfrey Hounsfield
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  • Figure 2: Hounsfield's sketch
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  • Figure 3: First CT scanner
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