Medical imaging often involves the solution of mathematical inverse problems. This means that cause (the properties of living tissue) is inferred from effect (the observed signal). http://en.wikipedia.org/wiki/Medical_imaging

Blimey, I thought that was what I had been studying history for back at Cambridge. You start off with events, a war say, and then work backwards to the cause. And now you tell me that’s about inverse maths! If only I had known at the time..