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"They are distinguished from gamma rays in that they are, by definition, produced by man made devices, X-Ray tubes, as opposed to being from sources in nature, generally nuclear decay sources." - This is not strictly true. X-rays are also produced naturally as the result of electron transitions between electron orbits. The x-rays we use for medical imaging are emitted to conserve energy when a charged particle is rapidly deccelerated and are collectively known as Brehmsstrahlung or 'Braking radiation'. Gamma rays are indeed the result of a natural re-arrangement of the nucleus of an atom.