The Evolution of CT Scan Clinical Trials
On October 1, 1971, CT scanning was first introduced by Godfrey Hounsfield into medical practice with a successful scan on a patient at the Atkinson Morley Hospital in Wimbledon, London using a prototype scanner. It is now almost forty years since that date which means that many of today’s radiologists have grown up in a world where there has always been computed tomography. Technology quickly becomes adopted and we happily take it for granted. Although today’s CT scan clinical trial technology is absolutely astounding, I still find it fascinating to discover some of the lesser known facts surrounding its evolution.
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Godfrey Hounsfield was a scientist working in the central research laboratory of EMI, (Electric and Musical Industries Ltd) in the UK. Hounsfield conceived the idea of a tomographic X-ray scanner in 1967 and fortunately at the time, EMI which was the Beatles’ record company, having sold over 200 million of the Fab Four’s singles, was able to fund Hounsfield to do his research. As a direct result of The Beatles’ success, he was able to devote about four years developing the CT scanner from its 1968 prototype to something that could be used in a clinical trial setting. What was interesting was that EMI’s research had initially estimated a worldwide need for only 25 of the machines, a slight under estimation for sure.
The initial prototype CT scanner used in clinical trials shown here had some less than inspiring specifications:
- Scan time 9 days
- Reconstruction 2.5 hours
- Print Image 2 hours
- Resolution 80 x 80
Hardly the kind of specs to get customers excited. However, the first production x-ray CT machine (called the EMI scanner) was limited to making tomographic sections of the brain, but acquired the image data in about 4 minutes (scanning two adjacent slices) and the computation time was about 7 minutes per picture.
CT Scan Clinical Trials
This initial CT scanner first used in clinical trials required the use of a water-filled tank with a pre-shaped rubber "head-cap" at the front, which enclosed the patient's head. The water-tank was used to reduce the dynamic range of the radiation reaching the detectors (between scanning outside the head compared with scanning through the bone of the skull).
The images were still relatively low resolution, being composed of a matrix of 80 x 80 pixels, the same as the prototype. Which raises the question, why 80 by 80? Eighty is a most unlikely number, not like the binary based resolution numbers of today’s digital images such as 256, 512 or 1024. The answer is purely analog. The scanning area on the prototype was ten inches by ten inches and the old lathe bed on which the scan box was mounted had a screw mechanism which had eight turns to the inch. Taking an x-ray transmission reading for each complete turn of the screw meant that the ten inches scan area required eighty readings. And there you have it, eighty by eighty. The CT scan clinical machine used the same screw pitch as the prototype, presumably to maintain the same reconstruction software. The “high resolution” scan took two readings for every turn of the screw, thereby producing a magnificent 160 by 160 image.
The CT scanner turned out to be probably the most revolutionary development in medical imaging of the century, with global sales far exceeding the originally estimated twenty five! Hounsfield received numerous awards in addition to the Nobel Prize in 1979 which he shared with Allan Cormack of Tufts University who had independently being developing the theoretical aspects of tomography. Hounsfield was appointed Commander of the British Empire in 1976 and knighted in 1981. In 1975, he was elected to the Royal Society. He never married and died in 2004, his name is forever immortalized in the Hounsfield scale used on every CT scanner.
So whatever happened to the EMI scanner? Well that is an entirely different story of corporate mergers, takeovers and intrigue. Did you ever hear about the M250? That story will have to wait for another time. In the meantime, if you have any questions regarding CT scan clinical trial applications, please feel free to comment below.