Optical performance studies of an all-polymer air-core scintillation dosemeter for brachytherapy

Plastic scintillation dosemeters have gained significant interest for invivo dosimetry in high-dose rate brachytherapy (BT) due to their favourable dosimetric properties. However, their clinical utility is limited by Cerenkov radiation, which can contribute over 50% of the signal, depending on the source position. The current dosemeter based on silica air-core (AC) light-guide was proven to be highly accurate; however, its high light loss and its mechanical rigidity limit its use for invivo BT dosimetry with flexible applicators. In the present work, a novel flexible all-polymer dosemeter with silver-coated polytetrafluoroethylene (Ag-PTFE) light-guide was built and compared to a solid-core light-guide dosemeter (standard dosemeter), using Geant4 Application for Tomographic Emission simulations. A reduction of the Cerenkov noise in the signal of this AC dosemeter was found below 0.3%, independently of the source position. On the other hand, the light collection efficiency was found to be ~40% smaller than in the standard dosemeter. We show how it is possible to further reduce this difference to ~20% and discuss the optimal design of this all-polymer Cerenkov-free dosemeter.