Motion compensation with a scanned ion beam: a technical feasibility study

Sven Oliver Grözinger,Thomas Haberer,Christoph Bert,Eike Rietzel,Gerhard Kraft

doi:10.1186/1748-717x-3-34

Sven Oliver Grözinger, Thomas Haberer + Show 3 more

Open Access

https://doi.org/10.1186/1748-717x-3-34

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Abstract

BackgroundIntrafractional motion results in local over- and under-dosage in particle therapy with a scanned beam. Scanned beam delivery offers the possibility to compensate target motion by tracking with the treatment beam.MethodsLateral motion components were compensated directly with the beam scanning system by adapting nominal beam positions according to the target motion. Longitudinal motion compensation to mitigate motion induced range changes was performed with a dedicated wedge system that adjusts effective particle energies at isocenter.ResultsLateral compensation performance was better than 1% for a homogeneous dose distribution when comparing irradiations of a stationary radiographic film and a moving film using motion compensation. The accuracy of longitudinal range compensation was well below 1 mm.ConclusionMotion compensation with scanned particle beams is technically feasible with high precision.

Highlights

Intrafractional motion results in local over- and under-dosage in particle therapy with a scanned beam
Lateral compensation performance was better than 1% for a homogeneous dose distribution when comparing irradiations of a stationary radiographic film and a moving film using motion compensation
Motion compensation with scanned particle beams is technically feasible with high precision

Summary

Introduction

Intrafractional motion results in local over- and under-dosage in particle therapy with a scanned beam. Geometric margins are commonly used to account for intra-fractional target motion [1,2]. These margins inevitably lead to inclusion of healthy tissue in the treated volume. Treatments are delivered in small partial doses that only result in adequate total dosage if they match as intended. In anatomy's eye view, target motion leads to relative displacement of partial dose depositions and results in local over- and under-dosage. The target volume is divided in slices corresponding to equal ion energies.

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