This is a completely different way of using ionising radiation to get pictures of internal organs. Instead of sending X-rays through the body from an X-ray machine outside it, these pictures are produced by rays coming from tiny amounts of radioactive substances inside the body. Although this probably sounds less safe than X-rays, the amount of radiation involved is often less than with X-rays of the same part of the body.

Say, for example, we want to get a picture of the liver. One of the liver’s normal jobs is to keep the blood pure by removing certain substances from it. When such a substance is injected into the blood, it is concentrated in the liver within a short time. If that substance has been made radioactive, it sends out rays through the body which can be detected with something similar to an X-ray plate. The picture produced in this way shows us the shape, size ancU<5cation of the liver and which parts are working normally. Any part of the liver which has been so badly damaged that it can’t do its normal job will show up as a ‘hole’, where there is little or none of the radioactive substance.

*70/40/1*