[Definition of volumes in external radiotherapy: ICRU reports 50 and 62].

Prescribing and achieving radiotherapy require accurate definitions of the target volumes and of the dose to be delivered in them. The need for the availability of a coherent vocabulary, recognized from local to international levels, has justified the publication, by the ICRU, of two reports related to external radiotherapy, the Report 50 (1993) and the Report 62 (1999). This paper presents the main propositions of the ICRU for the definition of the volumes, as well as comments and recommendations for their use.