ABSTRACT
This chapter deals with a problem that is central to the theme of the book-namely that ionising radiation, even at very low doses, is potentially capable of causing serious and lasting biological damage. If this were not so, steps that are taken to reduce patient doses, for example, the use of rare earth screens, would be unnecessary and generally undesirable. Furthermore, the amount of physics a radiologist would need to know would be greatly reduced and this book might not be necessary!
