Evaluating out-of-field doses during radiotherapy of paediatric brain tumours using lead shielding and flattening-filter free beams.

Paediatric radiotherapy comes at the expense of increased risk of late effects due to out-of-field dose caused not only by the treatment itself but also by image guidance. This study examined how the out-of-field dose to selected radiosensitive organs was affected by applying a 1 mm lead shielding during delivery of volumetric-modulated arc therapy (VMAT) for paediatric brain cancer. The study also investigated how the out-of-field dose to the same organs was affected by the use of flattening-filter free (FFF) beams.