S1736
Physics - Dose prediction/calculation, optimisation and applications for particle therapy planning
ESTRO 2026
standard four-step feedback to reduce beam-on time. The first pulse delivers ~85% of the target charge, and the second corrects the residual, maintaining dose accuracy within ±2%.System log analyses from demonstration runs at Mevion (Littleton, MA) quantified timing parameters, including energy layer switching (~50 ms), spot transitions (~1.3 ms per pulse), and charge delivery time. Delivery simulations incorporated these metrics to estimate total field time (Fig. 2).
Damage. DNA. 2024;4(1):34.4- Wang, W., et al. Modelling of Cellular Survival Following Radiation- Induced DNA Double-Strand Breaks. Sci Rep. 2018; 8:16202.5- Y. Furusawa, et.al. Inactivation of Aerobic and Hypoxic Cells from Three Different Cell Lines by Accelerated 3He-, 12C- and 20Ne-Ion Beams. Radiat Res. 2000;154(5):485. Keywords: Biological dose, Damage-potential metrics, MoD High-speed proton therapy within a short breath- hold: A clinically feasible framework for ultra-fast, motion-robust delivery Vivek Maradia 1 , Nick Yue 2 , Adam Molzahn 2 , Jingqian Wang 2 , Mark Pankuch 3 , Serdar Charyyev 1 , Billy W Loo Jr. 1,4 1 Department of Radiation Oncology, Stanford University, Stanford, USA. 2 -, Mevion Medical System, Littleton, USA. 3 Department of Medical Physics, Northwestern Medicine Proton Center, Warrenville, USA. 4 Stanford Cancer Institute, Stanford University, Stanford, USA Proffered Paper 2555 Purpose/Objective: Proton therapy offers superior dose conformity but is limited by long delivery times and motion sensitivity, particularly for thoracic tumors. Delivering a full field within a short breath-hold (5–10 s) would overcome this constraint. We present a clinically implementable framework for fast proton therapy using an existing synchrocyclotron machine (MEVION S250-FIT) to enable sub-10-second field delivery without mechanical modifications. Material/Methods: A three-part delivery optimization was developed (Maradia et al 2025):Integrated Shoot-Through (ST) and Bragg-Peak (BP) Beams: The method combines high-energy ST beams at the tumor periphery with conventional BP beams centrally to sharpen the lateral penumbra while maintaining depth conformity (Fig. 1c). Eight non-small-cell lung cancer (NSCLC) cases (target volumes 100–1000 cc) were replanned using RayStation 2024B with a validated MEVION S250-FIT beam model. Plans were compared to standard adaptive-aperture (AA) BP plans in terms of dose conformity, homogeneity, and organ-at-risk (OAR)
Results: The combined ST + BP approach achieved full-field delivery in <10 s for all cases, reducing delivery time by >90% relative to conventional adaptive-aperture (AA) plans. Dosimetric quality was preserved, with <2% variation in dose homogeneity and comparable organ- at-risk sparing. The NN scanning algorithm reduced lateral scanning time by 80%, and the two-pulse feedback maintained precise dose control. Estimated total delivery times, including energy layer switching, remained below 10 s per field (Fig. 2).
sparing.Nearest-Neighbor (NN) Scanning Optimization: Conventional line-by-line spot
sequencing was replaced by a dynamic NN algorithm that identifies the closest undelivered spot within each energy layer (Fig. 1 d and e). This reduces long magnet transitions beyond 7.8 mm, decreasing layer scanning time by >80%.Two-Pulse Feedback Dose Control: A simplified two-pulse regulation scheme replaces the
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