Traceability to absorbed-dose-to-water primary standards in dosimetry of brachytherapy sources used for radiotherapy

In the current brachytherapy practice, the procedures to determine the absorbed dose imparted to the patient are affected by an uncertainty higher than in radiotherapy with external beams. That could reduce the success of brachytherapy treatments. Most of the uncertainty is due to a lacking metrology: no absorbed-dose primary standards are so far available to assure direct traceability in dosimetry of brachytherapy sources. This paper outlines the project "Increasing cancer treatment efficacy using 3D brachytherapy", co-funded in the framework of the project iMERA-Plus according to the Grant Agreement No. 217257 between the European Commission and the European Association of National Metrology Institutes. The aim of the project is to develop methods for the direct measurement of the absorbed dose to water and to extend the use of this reference quantity to brachytherapy dosimetry with an uncertainty on the dose delivered to the target volume less than 5% (k=1) at clinical level. The present project will potentially increase the accuracy and safety of brachytherapy to a level comparable to that typical of radiotherapy with external accelerator beams.