Fig. 4From: Improve the dosimetric outcome in bilateral head and neck cancer (HNC) treatment using spot-scanning proton arc (SPArc) therapy: a feasibility studya The average estimated delivery time per fraction varies along with the ELST with p-values on the top of the columns. b Normal tissue complication probability (NTCP) model for parotid salivary flow (solid curve). The NTCP value denotes the probability of a reduction in salivary flow to < 25% of the pretreatment flow at ≤6 months after radiotherapyBack to article page