ABSTRACT
In Part B, Gordon Steel describes the process whereby ionising radiation acts directly on
the DNA of the nucleus causing cell death, as well as the mechanisms for subsequent repair.
For large doses of radiation, the damage, which may occur early or late in the life of the
organism, is more or less predictable and its severity may be determined by the magnitude of
the dose and the timing of its delivery. For this reason, such damage is described as determi-
nistic. In general, the dose-response function is sigmoid and exhibits a threshold. This
threshold is large compared to the doses that will be experienced by staff and public, and
with the rare exception of the foetus of a pregnant patient undergoing therapy, deterministic
effects will not be discussed within this chapter*.
