Fig. 1.

Delineation variation in case 1 for 20 observers. 1A (phase 1). The GTV of the primary tumour was delineated by 20 observers on CT, with available clinical and diagnostic information. 1B (phase 2). After fusion of the FDG-PET scan, the GTV was adjusted based on the visual interpretation of the FDG-PET scan. The colour wash image indicates the intensity of the SUV signal. This case contained satellite lesions proximal of the tumour. Although the presence of satellite lesions was included in the clinical information, these were included in the GTV by only 9 and 11 of the 20 observers in phase 1 and 2 respectively.