Creating a Transparent and Convex Objective Function for Intensity-Modulated Radiotherapy

This paper considers the objective functions currently being used in Intensity-Modulated Radiotherapy. In particular, we argue that there are three key features that any objective function should have. It should be convex, biologically relevant, and easily understandable. None of the current methods possess these features. To address this problem, we develop a new, two-tiered approach, based on intra- and inter-structural scoring functions. The Equivalent Uniform Dose (EUD) is one such intra-structural scoring function, so we develop the Linear Expenditure System as an inter-structural scoring function and show that this function, when combined with the EUD satisfies the three key properties. We then consider an alternative to the EUD, the n-part EUD. This function allows physicians to have greater control over patients’ dose distributions. ∗There are many people to whom I owe a deep debt of gratitude for their assistance in this project. Doron Levy has been an excellent thesis advisor, first pointing me in the direction of this research topic, then supporting me in any way he could. The expertise of Lei Xing and Edi Schreibmann has been invaluable. Without them I would know nothing about radiation oncology. For her clinical wisdom that has motivated much of my work, I am indebted to Cathy Su. I am also grateful to Jay Bhattacharya for putting me in touch with Dr. Su and discussing my project with me at great length. Finally, I would never accomplish anything were it not for the support of my friends and family. In particular, I wish to honor Elizabeth Madjlessi, whose volunteer work has done more for the care of cancer patients than any research I have pursued. Al