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内容記述 |
Aims: Significant reductions in treatment delivery times for ion therapy were made possible for synchrotron-based systems through the development of fast raster-scanning and multi-energy extraction (MEE) operation. Nonetheless, the temporal structure of beam delivery, beam delivery time (BDT) and beam delivery efficiency (BDE) remain unexplored or insufficiently characterized. The aim of this study is to perform a comprehensive analysis of the temporal structure of beam delivery for raster-scanned helium-, carbon-, oxygen-, and neon-ion beams. A machine-specific BDT model was established towards novel delivery strategies like ion arc therapy.Material & methods: The temporal structure of beam delivery was analyzed and modeled, based on parameterization of beam-on (ton) and beam-off (toff) times per energy layer (EL), such that the total BDT (TBD) equals ∑(ton+toff) of all ELs. ton was simply predicted, considering beam intensity and number of particles per EL, while toff was modeled by the number of particles in the synchrotron, time duration for a new synchrotron cycle, and time durations to reduce or maintain the beam energy. Model validation was performed by comparing predicted and measured TBD for clinical treatments.Results: Model predictions for ton were within <0.1% of measurements, while deviations in toff predictions versus measurements varied, mainly due to uncertainties in time durations to maintain the energy and reduce the energy at low energy region. Average measured TBD was 96 s and model prediction errors were within ~3.8(±4.5)% (fig.1a), demonstrating acceptable agreement across patient cohorts and ion species. The largest deviations occurred for H&N cases which commonly use low-energy beams. BDE (∑ton/TBD) was ~20-40% (fig.1b), signifying potential for further BDT optimization.Conclusions: This work developed and validated the first BDT model for helium-, carbon-, oxygen-, and neon-ion therapy. The model will be used for machine performance evaluation, BDE optimization, and optimization of ion arc therapy. |
