Here is an idea I had for a way to deduce the internal structure of an organic object using it's natural radioactivity. The set-up is an array of gamma ray detectors located circularly around the object. By detecting both the position and direction of the gamma rays (obviously impossible to get them both accurately due to quantum mechanics but we can get a certain amount of information) emerging from the object one should be able to deduce the internal structure of an object. Now apparently a human being only gives off about 500 gamma rays per second. So it would not be very useful for a human as they would have to sit a long time. But for something like a tissue sample or a plant or even a radioactive fossil one could wait several hours and build up a 3D image. Assuming roughly the more dense part of an object was more radioactive you would get a density map. Consider a radioactive pea sitting off-center from the array of detectors giving of thousand of gamma rays. It would create a unique pattern of gamma ray information which could be, by use of Fourier analysis, be used to deduce the exact location of that pea. Similarly with two peas. etc. I think it would work best on organic objects since the gamma radiation they produce is more likely to escape to the outside than denser objects which absorb their own internal radiation more. What do you think the feasibility of this is with current technology? I think the limiting cost is the gamma ray detectors which are expensive. And presumably you'd need an array of them to get good information. Maybe it would cost as much as the LHC! For very radioactive materials you could save money just using one Geiger counter and moving it around but then you'd miss most of the photons so it is not most efficient. The idea behind this is that I'm interested in how to build a personal cheap internal scanner. Edit: Actually I think its all ready been invented: "Gamma camera" wikipedia. Although my version would just use natural radioactivity instead of inducing it.