Abstract # 2216 Analysis of Interfractional Set-up Errors and Intrafractional Organ Motions during IMRT for Head and Neck Cancers toDefine an Appropriate PTV-margin

Presenter: Suzuki, Minoru

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In IMRT for head and neck cancers, geometrical uncertainties including interfractional set-up errors and intrafractional organ motions have great impact on steep dose gradients between the planning target volume (PTV) and the planning organ at risk volume (PRV). Knowledge of those uncertainties is essential for designing appropriate PTV­margins. At our institution, 5-mm margin had been adopted as the PTV-margin for head and neck IMRT. The purpose of the present study was to verify whether the 5-mm PTV-margin was appropriate by analyzing the geometrical uncertainties in IMRT for head and neck cancers prospectively.

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