ISO/ASTM 51650:2013 is a practice for using a cellulose triacetate (CTA) dosimetry system to measure absorbed dose in materials irradiated by photons or electrons in terms of absorbed dose to water. The CTA dosimetry system is classified as a routine dosimetry system. The CTA dosimeter is classified as a type II dosimeter on the basis of the complex effect of influence quantities on its response. ISO/ASTM 51650:2013 is one of a set of standards that provides recommendations for properly implementing dosimetry in radiation processing, and describes a means of achieving compliance with the requirements of ASTM E2628 for a CTA dosimetry system. It is intended to be read in conjunction with ASTM E2628.