Example for the delineation of the RP volume. Two CT scans of the chest to confirm the clinical diagnosis and showing the maximum expansion of RP were fused with the treatment plan and both the pneumonitic lung areas at the time point of clinical appearance and at maximum expansion were delineated. In this example, the RP at the time point of clinical appearance (green contour) was located outside the 50 Gy isodose (yellow), mainly in lung areas with doses below 30 Gy. The larger RP volume at the time point of maximum expansion of RP (light blue contour) was also observed within the lung areas receiving more than 50 Gy (yellow 50 Gy isodose and red coloured the 60 Gy isodose) encompassing the bottom of the PTV (orange contour)