Ionizing radiation has been used in medicine for more than a century and has proven to be an essential component of modern medical diagnosis and treatment. The technology has made much progress in the past decades, in X-ray imaging through the development of digital and computerized technology, in nuclear medicine through the introduction of novel radioisotopes and techniques, and in radiotherapy through sophisticated computerized treatment planning and novel techniques for more precise delivery of the radiation to the tumour.

At the same time, ionizing radiation is a cause of concern because the exposure of the human body may cause health detriment. At present, the overall population exposure due to medical procedures hugely exceeds any other man-made exposure. The protection of the patients and other individuals exposed in medical practice, is therefore one of a main priority task for the European Commission under the Health and Safety Chapter of the Euratom Treaty.