Fig. 1

An illustrative example of a contoured ultra-central lung tumor case. The relative locations of tumor and OAR are indicated; IGTV (red), PTV (blue), proximal bronchial tree (yellow), esophagus (green), heart (maroon), and healthy lung (cyan). Here, the PTV volume is 83.1 cm³ and 2.2 cm³ overlap with the proximal bronchial tree