Hitting the target: analysis of delineation and dosimetric uncertainty in radiotherapy

Through advances in radiation delivery systems and image guidance, the accuracy and precision of radiation therapy has improved in recent times. Some aspects with respect to the accuracy and precision with which treatments are prescribed and planned have also improved, however it has not been to the same extent. Radiotherapy has moved from 2D to 3D treatment planning and now incorporates multimodality imaging into the contouring process, but there is still variation in tumour delineation. This thesis is an investigation into the impact of contouring, planning, and organ motion variation on dosimetry and modelled outcome in a variety of disease scenarios. The effect of contouring uncertainty in the lung was investigated with a retrospective dataset of nonsmall cell lung cancer patients. Planning uncertainty due to planner experience was studied using a head and neck case and the influence of organ motion was considered in the post-prostatectomy setting. Finally, the techniques developed to analyse contouring variation were applied to a gynaecological clinical trial benchmarking dataset to incorporate contouring uncertainty into the trial sample size calculation...