Lung organ-at-risk volumes: A survey of practice and the need for a consistent definition in the 4DCT era

Abstract

Introduction: In the 4DCT era, the definition of lung organ-at-risk (OAR) volumes for dose–volume histogram (DVH) calculation is unclear, introducing potential for variability in practice. We aimed to identify definitions used clinically and evaluate the magnitude of DVH differences between these. Methods: We surveyed Australian & New Zealand departments about lung radiotherapy protocols including lung OAR volume definition. We used these definitions to calculate lung DVHs on 10 patients prescribed lung IMRT (60–66 Gy/30–33 fractions). We calculated mean lung dose (MLD), V20 and V30 for ‘Lungs – PTV’, ‘Lungs – CTV’, ‘Lungs – iGTV’ (internal GTV in all respiratory phases) and ‘Lungs – GTV_EX’..