Beam-orientation optimisation of IMRT: clinical application to parotid gland tumours

The potential of IMRT to reduce toxicity was investigated. Initially, a treatment plan was set-up on the CORVUS1 inverse treatment planning system using nine equi-spaced beams. The goal of the inverse plan was to reduce the dose to the cochlea and the oral cavity compared to the conformal wedged pair technique. The plan reduced the dose to the cochlea and to a lesser extent reduced the volume of the oral cavity receiving high-dose, and also improved the PTV homogeneity. Unfortunately, compared to the conformal wedged pair technique, the IMRT plan greatly increased the dose to the contralateral parotid gland with 73% of the OAR receiving dose in excess of 6 Gy.