How Academic Research Solved the Puzzle of MRI and CAT Scanning

Computed Tomography: a Technology Transfer Story

You may have heard the old story about the professor explaining why he partnered on a project with an industrial consortium. “Well, we had the experience and they had the money, and when it was done, we had the money and they had the experience.”

Notwithstanding the unsavory notion that this anecdote projects, Technology Transfer, the moving of knowledge from the academic experts to those who develop products, has a rich and productive history. Perhaps the majority of significant products and entire industries have followed this well-worn path. Electronics has especially benefitted from this mode of development, and one of the best examples is in the field of medical imaging.

Tomography is the “T” in CAT scans and PET scans, and is also the underlying technique in MRI. The dictionary describes it as a method of producing 3D images of the internal structure of a solid object by recording of the differences in the effects of energy wave passage through the structures.

That sounds straightforward enough but as usual, the devil is in the details. Early medical experimenters who tried to improve on the single-plane x-ray by using an array of detectors were unsuccessful. They correctly recognized that each detector was a line integral through the object to be imaged and by ‘back projecting’ that information, they reasoned that the desired image would appear. But although they carefully developed the algorithm using a common-sense approach and equally carefully took the measurements, the resulting images were hopelessly distorted and smeared.


Science has a venerable history of publishing its results, including problematic ones, and one of the reasons is that someone may be able to offer an informed opinion for improvement. It is sometimes especially helpful to have a cross-disciplinary group of experts in the audience, as can happen in a university or research lab, and that is what happened in this case. Mathematicians came to be intrigued by the tomography problem. In due course, one became aware of a similar problem in a considerably different application, astronomy, and the solution developed several generations before, called a Radon Transformation, turned out to be directly applicable to the medical problem!

In brief, the problem was that the line integrals projected through the object non-uniformly, depending upon the geometry of the detector array, with some parts of the object getting over-sampled (and thus getting too much weight in the reconstruction) and some getting undersampled. The Radon Transform, much like a Fourier transform or other filter operation, acts on the data field, accounts for the geometry and all of a sudden, humanity had a new era in medicine. Engineers took it from there. All sorts of imaging systems for every part of the body have now been produced, and countless lives have been saved in the ensuing diagnoses.

Computed tomography is used beyond medicine in such other vital areas such as energy exploration, (where, in this case, the earth is the patient), industrial quality control, genetics, and even jewelry! (Is there a flaw in that diamond? Can we zap it with a laser?)

Meanwhile, every day, interdisciplinary conferences and seminars are being held, putative partnerships are being formed, and some of them may come to affect our lives as profoundly as this one. Some of these Tech Transfer events are facilitated by national governments, and sometimes their militaries; atomic energy, aerospace, and the computer come quickly to mind. Perhaps the most noteworthy collaboration of all time was the set of projects that culminated in the Internet. And the internet, in return makes it easier than ever to partner and collaborate on a given problem, because someone out there has the money and someone else surely has the experience.