A review of the scientific basis for radiation protection of the patient.

: The use of ionising radiation in medicine is the single largest man-made source of population exposure. Individual and collective doses to patients arising from the medical use of ionising radiations continue to rise significantly year on year. This is due to the increasing use of medical imaging procedures in modern healthcare systems as well as the continued development of new high dose techniques. This paper reviews the scientific basis for the principles of radiation protection as defined by the International Commission on Radiological Protection. These principles attempt to include exposures arising from both medical and non-medical applications within a common framework and have evolved over many years and changing socio-economic considerations. In particular, the concepts of justification and ALARA (doses should be as low as reasonably achievable), which underpin the principles for medical exposures are assessed in terms of their applicability to the scientific process and relevance to a rapidly changing technologically-led healthcare system. Radiation protection is an integral component of patient safety in medical practices and needs to be evidence based and amenable to the scientific process. The limitations imposed by the existing philosophy of radiation protection to the development of a quantitative framework for adequately assessing the performance of medical imaging systems are highlighted. In particular, medical practitioners will require quantitative guidance as to the risk-benefits arising from modern X-ray imaging methods if they are to make rational judgements as to the applicability of modern high-dose techniques to particular diagnostic and therapeutic tasks. At present such guidance is variable due to the lack of a rational framework for assessing the clinical impact of medical imaging techniques. The possible integration of radiation protection concepts into fundamental bio-medical imaging research activities is discussed.