Optimization Towards Dose Carving for Head and Neck Treatment Planning

Radiation therapy aims to deliver high radiation dose to tumor target with minimal exposure to surrounding normal tissue. However, he physics of energy decomposition and mechanical limitations restrict the achievable dose distribution, necessitating tradeoffs between target coverage and normal tissue sparing. Treatment planning is the process of obtaining control parameters to yield such a dose pattern. Dose volume histograms (DVHs) are common tools in radiation therapy treatment planning to characterize plan quality and used as objective functions. Despite their efficacy as a compact statistical summary of dose pattern, DVHs provides limited spatial information as a report quantity and insufficient control as optimization objectives. This limitation is particularly severe for treatment site with complex geometry, as in the case of head and neck, with the presence of multi-level target volumes and various adjacent organs at risk (OARs). This paper discussed a method for dose carving, by modifying the optimization objective in the treatment planning system. Motivated by the emergent compressive sensing techniques, we introduce an objective function whose minimization leads to more direct tradeoff between target coverage and OAR sparing, sharper dose dropoff and better target dose homogeneity, achieving a better “carving” in the dose distribution. This principle, though generally applicable to all sites, is particularly beneficial for cases with complex geometry, such as head and neck planning.