ESTRO 2024 - Abstract Book

S4218

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2024

Figure 2: Information on tumor location, range of motion, and results on variation in target volume coverage due to interplay.

Conclusion:

The interplay of scanning pencil proton beams and breathing motion is a complex interaction to model precisely. From this study, we can see that the dose perturbation due to interplay is acceptable for scanned proton beams when the range of tumor motion is under 1.5cm and at least 3 fields are used, with no additional repainting required. This amount of motion is the upper limit of motion accepted for lung/liver cases (photon and proton) in our center, beyond which some motion reduction technique is applied (abdominal compression, breath hold, etc.). However, the effect of larger motion amplitudes on dose perturbation due to interplay will still be investigated as the next phase of this study, to determine a relationship between motion and the amount of rescanning required.

Keywords: Interplay, proton therapy, pencil beam scanning

References:

Rana S, Rosenfeld AB. Investigating volumetric repainting to mitigate interplay effect on 4D robustly optimized lung cancer plans in pencil beam scanning proton therapy. J Appl Clin Med Phys. 2021 Mar;22(3):107-118. doi: 10.1002/acm2.13183. Epub 2021 Feb 18. PMID: 33599391; PMCID: PMC7984493. Siregar H, Bäumer C, Blanck O, Chan M, Engwall E, Plaude S, Spaan B, Timmermann B, Wulff J. Mitigation of motion effects in pencil-beam scanning - Impact of repainting on 4D robustly optimized proton treatment plans for hepatocellular carcinoma. Z Med Phys. 2022 Feb;32(1):63-73. doi: 10.1016/j.zemedi.2020.08.001. Epub 2020 Oct 31. PMID: 33131995; PMCID: PMC9948857.

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Poster Discussion