Technetium-99mAlthough much of this sub-topic deals with cancer treatment, technetium-99m, the most widely used radioisotope in medicine, is only used in diagnostic radiotherapy. It is ideal for this purpose as it is a gamma radiation emitter with a half-life of 6.0 hours. This means that within 24 hours 94% of it will have decayed to technetium-99. It also has a short biological half-life of one day, which means that...