Improving Target Definition for Head and Neck Radiotherapy: A Place for Magnetic Resonance Imaging and 18-Fluoride Fluorodeoxyglucose Positron Emission Tomography?

Defining the target for head and neck radiotherapy is a critical issue with the introduction of steep dose gradients associated with intensity-modulated radiotherapy. Tumour delineation inaccuracies are a major source of error in radiotherapy planning. The integration of 18-fluoride fluorodeoxyglucose positron emission tomography (18FDG-PET) and magnetic resonance imaging directly into the radiotherapy planning process has the potential to greatly improve target identification/selection and delineation. This raises a range of new issues surrounding image co-registration, delineation methodology and the use of functional data and treatment adaptation. This overview will discuss the practical aspects of integrating 18FDG-PET and magnetic resonance imaging into head and neck radiotherapy planning.