A dose-volume based tool for evaluating and ranking IMRT treatment plans

Abstract

External beam radiotherapy (RT) is commonly used for patients with cancer. While tumor shrinkage and palliation are frequently achieved, local control and cure remain elusive for many cancerous diseases. With regard to local control, the fundamental problem is that RT-induced normal tissue injury limits the dose that can be delivered to the tumor. While intensity modulated radiation therapy (IMRT) allows for the delivery of higher tumor doses and the sparing of proximal critical structures, multiple competing plans can be generated based on dosimetric and/or biological constraints that need to be considered/compared. In this work, an IMRT treatment plan evaluation and ranking tool, based on dosimetric criteria, is presented. The treatment plan with the highest uncomplicated target conformity index (TCI+) is ranked at the top. The TCI+ is a dose-volume based index that considers both a target conformity index (TCI) and normal tissues sparing index (NTSI). TCI+ is designed to reflect clinical judgment of the merit of a treatment plan. To demonstrate the utility of this tool, several-competing lung and prostate IMRT treatment plans are compared. Results show that the plan with the highest TCI+ values accomplished the competing goals of tumor coverage and critical structures sparing best, among rival treatment plans for both treatment sites. The study demonstrates that i) dose-volume based indices, which summarize complex dose distributions through a single index, can be used to automatically select the optimal plan among competing plans and ii) this dose-volume based index may be appropriate for ranking IMRT dose distributions.