Abstract
Image Guided Intensity Modulated Radiotherapy (IG-IMRT) incorporates novel imaging strategies into IMRT planning and delivery. FDG-PET/CT imaging may be used to identify potentially radioresistant tumour cell populations in head and neck cancer (HNC). Dose-painting with IMRT is a novel technique which provides an opportunity to widen the therapeutic window by dose escalation to radioresistant subvolumes. The purpose of this thesis was to evaluate the feasibility of this technique, to provide methodology for identification of the FDG-avid region and to inform on a reasonable dose level to use in a future phase I clinical study investigating dose-painting to the FDG-avid target volume. This technique requires confidence in the quality of geometric and dosimetric accuracy of delivery and this issue was investigated in this thesis. Pre-clinical work included a comparison of five different FDG segmentation techniques. One of these techniques was used to identify the FDG-avid biological volume selected to receive dose-painting with IMRT in a planning study. Four dose levels were tested. Radiobiological modelling was used to determine an optimal dose level as the basis for a future clinical study and to determine the impact of using different FDG segmentation techniques. A clinical study was performed in patients with HNC to compare in-room volumetric imaging - cone beam computed tomography (CBCT) - with planar kilovoltage (kV) electronic portal imaging (EPI) for aspects of image guidance and to inform on appropriate planning margins. Pre-clinical work suggested that dose-painting with IMRT to the FDG-avid subvolume would be associated with increases in estimated tumour control probability (TCP) and with acceptable increases in normal tissue complication probability (NTCP). Verification using CBCT provided accurate data to guide treatment delivery and appropriate planning margins. The findings reported in this thesis provide valuable information that will inform the design of future clinical studies.