Characterisation of radiological properties of a brachytherapy moulding material

The use of a non-water-equivalent personalised mould for gynaecological brachytherapy treatments can result in a substantial dose reduction at the treatment site, compared to calculated dose, in lieu of a dose calculation algorithm capable of modelling non-water-equivalent materials. This study describes the characterisation of the radiological properties of a brachytherapy applicator moulding material. Simple line source correction factors for an ¹⁹²Ir source are obtained through Monte Carlo simulations and verified by film measurements. The dwell position corrections are used to estimate aggregate correction factors for dose deliveries that involve multiple dwell positions, in terms of treatment length, applicator radii and depth of reference dose. For the Fricotan moulding material used locally, the dose reductions varied from 1% for an applicator radius of 0.5 cm to > 4% for radii exceeding 2 cm. The method described in this paper could be used to develop correction factors for other non-water-equivalent moulding materials, in a TG-43UI dose calculation environment.