It was hailed as the biggest medical breakthrough since the stethoscope and the discovery of x-rays. This month, October 2011, St George’s Healthcare NHS Trust celebrates 40 years since the very first clinical use of computed tomography (CT).

CT scanning is a non-invasive medical imaging method, used to create 3D images of human organs. A CT scanner sends x-rays from one side of an object to the other, allowing it to calculate the density of the object it scans. The technology creates an image ‘slice’ by measuring an object’s ability to block the x-ray beam. These slices are assembled together and the 3D image produced allows clinicians to identify different tissues in the body, such as bone, muscle and tumours.

The world’s first CT scan on a patient was carried out at Atkinson Morley Hospital, in Wimbledon, now part of St George’s Hospital, on 1st October 1971. It was a brain scan performed by Sir Godfrey Hounsfield and Dr Jamie Ambrose, consultant radiologist. Sir Godfrey was subsequently awarded the 1979 Nobel Prize in Medicine. CT scanning was a revolutionary technology that dramatically improved patient safety by providing a non-invasive method to diagnose illness.

CT scanning remains a core service in the NHS today and St George’s Hospital’s Atkinson Morley Wing, named after the hospital which closed in 2003, is still home to some of the most advanced scanning equipment in the country. The hospital has three further scanners, including the newest in the Accident and Emergency Department which provides ultra fast scanning for patients that need immediate treatment following a major injury or stroke.

The earliest CT scanners took several minutes to create a still image slice of the body in the 1970s. The most modern machines take just seconds to scan the whole body today. The technology can now provide 3D images, and is so fast that in many instances it can replace more invasive tests, such as angiography.

Jane Adam, consultant radiologist at St George’s Hospital, said: “It is hard to overestimate what an absolute revolution CT was for medicine. Before CT, only really x-ray imaging was available, which could show the bones and lungs, but little else in detail. When the first CT scan was used, the brain tissue inside the skull could be visualised for the first time, and it was soon realised that CT could be used to see the rest of the organs of the body as well.

“Sir Godfrey Hounsfield was an interesting man and an amazing scientist, although personally unassuming and modest. Whenever he travelled, however, he insisted on sticking with the UK clock, so even in America he would hold meetings at UK times. He understood how important it would be to visualise the internal organs to understand disease. He lived to see his invention revolutionise medicine and contribute immensely to patient care. We have much to thank him for.’’

Notes to editors

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