[Basic concepts on protection in nuclear medicine].

We define the objectives of Radiation Protection in Nuclear Medicine and the general principles of the system of protection. Based on ICRP (International Commission on Radiological Protection) Publication 60 of 1990 we do an introduction to the ionising radiation effects and to the way to quantify the risk associated to them through the concept of "detriment". Detriment is a multi-dimensional concept and the distribution of "detriment" among organs is represented by the tissue weighting factors. Revised values for those factors are presented on ICRP Publication 60 in light mainly of the new epidemiological data from atomic bomb survivors. Based on those new data the Commission recommends a reduction of the dose limits for occupational and general public exposure. Finally we present practical measures of Radiological Protection grouped in the items staff, environment, transportation and patient protection. The last item is particularly emphasised because it is entirely dependent on clinical and technical criteria and because there are no limits to the dose to the patient, perfectly justified by the benefit to the patient.