Fig. 1From: A knowledge-based intensity-modulated radiation therapy treatment planning technique for locally advanced nasopharyngeal carcinoma radiotherapyThe overlapping between the left parotid (sky blue) and: (a) the CTV-ALL contracted with a distance of 5 mm (red); (b) the initial CTV-ALL (purple); (c) the CTV-ALL expanded with a distance of 5 mm (tan). The overlap volume fraction is defined as the overlapping volume divided by the volume of the left parotidBack to article page