ISO 21439:2009 specifies methods for the determination of absorbed-dose distributions in water or tissue that are required prior to initiating procedures for the application of beta radiation in ophthalmic tumour and intravascular brachytherapy^]. Recommendations are given for beta-radiation source calibration, dosemetry measurements, dose calculation, dosemetric quality assurance, as well as for beta-radiation brachytherapy treatment planning. Guidance is also given for estimating the uncertainty of the absorbed dose to water. ISO 21439:2009 is applicable to sealed radioactive sources, such as plane and concave surface sources, source trains of single seeds, line sources, shell and volume sources, for which only the beta radiation emitted is of therapeutic relevance.

The standardization of procedures in clinical dosemetry described in ISO 21439:2009 serves as a basis for the reliable application of beta-radiation brachytherapy. The specific dosemetric methods described in ISO 21439:2009 apply to sources for the curative treatment of ophthalmic disease, for intravascular brachytherapy treatment, for overcoming the problem of restenosis and for other clinical applications using beta radiation.

ISO 21439:2009 is geared towards organizations wishing to establish reference methods in dosemetry aiming at clinical demands for an appropriately small uncertainty of the delivered dose. ISO 21439:2009 does not exclude the possibility that there can be other methods leading to the same or smaller measurement uncertainties.