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Sittig DF, Ash JS, Ledley RS. The story behind the development of the first whole-body computerized tomography scanner as told by Robert S. Ledley. J Am Med Inform Assoc. 2006 Sep-Oct;13(5):465-9. Epub 2006 Jun 23. PMID 16799115. [PDF]

This JAMIA article provides an entertaining oral history of the invention of the whole-body CT scanner by Dr. Robert S. Ledley.

Dr. Ledley was a physics student at Columbia University, and later received a dental degree at NYU to support his physics work. He began his drive to build a whole-body scanner after his NIH funding was cut in 1970:

He says, “Well, I was going to buy this machine,” and he shows me a slick brochure, the EMI machine. It was a head scanner only. But what he didn’t know is that they didn’t have it yet. They just had a brochure!

So I looked at this book, and sure enough, you could see organs, but they were fuzzy. It was terrible; picture after picture. I didn’t see how they could use much of that. But at the same time, I read a paper in The Journal of Applied Physics. It was written by a fellow by the name of Cormack at Tufts. And he took a cylinder of aluminum and a cylinder of wood, with a hole in it, that the aluminum fit into, and he scanned it, one scan. And he said, “Well, it’s circular symmetric, so I’ll make a whole lot of scans, because they’re all the same.” Okay? And then he worked out the absorption coefficient of the aluminum and the wood, to a very large number of significant figures. And I thought to myself, “Man! that’s great! We can do it!” And I figured that I could make it.

So I went back to Dr. Luessenhop and I said, “I can make it, and it’ll be half the price” [of that quoted for the EMI scanner]; I didn’t even know what the price was!

Besides the CT scanner, Dr. Ledley made numerous breakthroughs in digital computer engineering. He is currently president of the National Biomedical Research Foundation, which he founded in 1960.

Image Credit: US Patent #3,922,552 Figure 1

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