The Invention of Computed Tomography
Research Models
Dustin Grinnell

The Invention of Computed Tomography

In 1969, Dr. James Ambrose, a neuroradiologist from Atkinson Morley’s Hospital in London, got a call from an engineer he had never met named Godfrey Hounsfield from EMI laboratories. Inspired from an idea which struck him on vacation, Hounsfield called Ambrose to introduce him to his recent work, reconstructing a 3D image of a box by considering it as a series of slices.

During their phone call, Hounsfield–already dismissed as a “crank” by many renowned radiologists–proposed an imaging device far superior to the commonly used X-ray machine, which produced fuzzy 2D pictures of brain structures. Like other radiologists Hounsfield had contacted, Ambrose dismissed Hounsfield’s ideas at first, but later–albeit reluctantly–agreed to a meeting. That eventual get-together led to the first Computed Tomography (CT) scanner, a machine that revolutionized diagnostic medicine and the way we look inside the brain.

Godfrey Hounsfield, the youngest of five children, was a tinkerer early on. Recollecting his childhood, set on his parent’s farm, he said, “I enjoyed the freedom of a rather isolated country life.” When he was a teenager, he would often take apart electronics, building tools and devices. He once built a rudimentary hang glider which he flew off stacks of hay behind his house, almost killing himself many times he later said of the memory. At the Magnus Grammar School, he showed strengths in math and physics. After graduation, he joined the Royal Air Force just before World War II, learning electronics and radar while he completed his service. He later studied electrical and mechanical engineering at the Faraday House in London and in 1951 joined the Central Research Laboratory at EMI laboratories where he worked on weapons systems and radar. It wasn’t until 1960 that he took an interest in computer technology and eventually imaging. When he called Ambrose in 1969, Hounsfield had already built a prototype of his invention, the first Computed Tomography scanner.

Tomography, the Greek word tomos means “slice” or “section.” Graphia means “describing.” Unlike an X-ray machine, which produces flat, 2D pictures of bone and tissues, Hounsfield’s device took multiple, thin photographic slices of objects, which could be later combined on a computer to create three-dimensional composite images.

In the late 60’s, working on a meager research budget of less than $40,000, Hounsfield and his team of three–an electronics expert, programmer and mechanic–built a prototype CT scanner on a lathe bed, overcoming repeated failed tries during development. “As expected,” Hounsfield said, “The program involved many frustrations, occasional awareness of achievement when particular technical hurdles were overcome, and some amusing incidents.”

Hounsfield’s early photographs were of pig bodies and human brains. His team’s first scanner took nine days to capture a full 3D image and worked by rotating around an object 1 degree at a time for 160 traverses, emitting gamma rays as its light source. Hounsfield later switched the energy source to x-rays, reducing the scanning time to 9 hours.

While the idea seemed promising to Dr. Ambrose on first meeting Hounsfield, the radiologist remembered Hounsfield’s presentation as vague, containing more promises than proof. “The conversation was…difficult,” Ambrose said looking back on the day. But Ambrose allowed Hounsfield to prove himself, sending a human brain from a local museum to EMI Laboratories. Five weeks later, Ambrose received the first brain images produced from a CT (See Picture). Immediately, he knew the field of medical imaging was changed forever.

Hounsfield and Ambrose began a lifelong partnership, working together to build a CT prototype for clinical use. In the beginning, their operation almost ended several times because of money issues, but a doctor at the Department of Health placed an early order for a machine, injecting the project with enough cash to continue.

In 1971, with enough funding and four newly built scanners, Hounsfield and Ambrose photographed the brain of patient with a frontal lobe tumor. “It looks exactly like the picture,” the surgeon remarked, referring to the tumor’s appearance on the scan. From 1973 to 1976, head-scanning CT machines were distributed to hospitals in England and the United States (whole-body scanners in 1976).

For their contribution to medical science, Hounsfield and Ambrose jointly won the BJR Barclay prize in the 1974. A year later, Hounsfield was elected to the Royal Society and in 1979 was awarded the Nobel Prize in Physiology and Medicine. Two years following the Nobel, he was honored with knighthood, becoming Sir Godfrey Hounsfield.

It was in 1972, at the 32nd Congress of the British Institute of Radiology, where Hounsfield and Ambrose first presented brain scans generated by CT in their talk, Computerised Axial Tomography–a presentation many audience members say they will never forget. Today, there are over 6,000 scanners in the US; 30,000 worldwide. In 2004, Godfrey Hounsfield passed away at the age of 84, leaving behind one of the most important inventions in medical science history.



Image Caption: First human brain scan by Computerized Tomography (1969)