ABSTRACT
As discussed in Section 12.5 there is ample evidence that ionising radiation is harmful to humans and it is important to remember that, almost always, the reason why doses are measured in radiology is to estimate the radiation risk. The reason for dose reduction is to minimise the risk, usually in respect of the possibility of stochastic effects, but occasionally the possibility of tissue reactions for interventional procedures carried out under X-ray control. As already discussed in several places in the book, especially Section 6.10 on quantum mottle, reducing the dose of radiation has an adverse effect on image quality. Therefore in the absence of risk to the patients much higher doses would frequently be used. The balancing of adequate image quality against dose and therefore risk is the process known as optimisation and we shall return to this idea in Section 13.6.
