Advancements in Brachytherapy Measurement Techniques

Brachytherapy has been used for over 100 years to treat cancer and continues to be a common delivery technique for many types of diseases. Primary brachytherapy standards based on air kerma or absorbed dose in water have been developed and fine-tuned in the last 15 years by several primary labs around the world to accommodate a variety of low- and high-energy brachytherapy sources. However, recent advancements have demanded that new standards be created to accommodate new source designs and more modern Monte Carlo-based treatment planning systems. This presentation will focus on the US-based approach to electronic brachytherapy standards and general strategies for new sources being developed including elongated and directional Pd-103 sources. An overview of the new air-kerma based standard at the National Institute of Standards and Technology (NIST) for electronic brachytherapy will be presented as well as the University of Wisconsin Variable Aperture Free Air Chamber (UW VAFAC) and how it has been used to determine the air-kerma strength of novel Pd-103 sources. In addition to these new air-kerma based devices, there is a need for new emitted-power based standards that may be better suited to work with modern Monte-Carlo based treatment planning systems. Results from a new cryogenic calorimeter developed by the University of Wisconsin Medical Radiation Research Center (UWMRRC) for determining the emitted power of low-energy brachytherapy sources will be presented as an alternative method to determine source strength.