SU-E-T-565: Effectiveness of Robust Optimization in Head and Neck IMPT Dose Distributions

Medical Physics
W LiuRadhe Mohan

Abstract

The effectiveness of IMPT may be significantly diminished by range and patient setup uncertainties. The purpose of this presentation is to evaluate the ability of robust optimization methods to desensitize H&N IMPT plans to uncertainties and their impact on plan optimality. We use a robust optimization method, in which the objective function value for a given iteration is computed using the 'worst case' dose distribution. The conventionally optimized PTV-based IMPT plans and robustly optimized plans were generated for 14 head and neck cancer cases. The dose standard deviation was calculated for every voxel and used to compute 'standard-deviation volume histograms' (SVHs). The area under SVH curves was used to quantify the plan robustness. In addition, D1cc doses for spinal cord and brainstem, mean doses Dmean for oral cavity and parotids, and D1% doses for other organs were used to assess plan optimality. D5% and D95% doses are used to assess target dose coverage and homogeneity. The plan optimality and robustness are then compared statistically by the pair t-tests using SPSS 19.0 software. Compared with PTV-based optimization, robust optimization provides significantly more robust dose distribution for both targets and organs ...Continue Reading

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