ESTRO 2025 - Abstract Book

S3467

Physics - Optimisation, algorithms and applications for ion beam treatment planning

ESTRO 2025

Table DVH parameters of the OARs for the 3 planning techniques

Conclusion: Compared with conventional VMAT technique, proton therapy demonstrated a greater capability to achieve highly non-uniform target doses for adaptive dose escalation while notably reducing the dose to adjacent critical structures. SPArc can further boost the local dose to these isolated, small but highly resistant sub-regions while achieving a lower dose to OARs. These dosimetric improvements may translate into better patient care in advanced HNSCC.

Keywords: Adaptive Radiotherapy, FDG-PET, Dose Escalation

References: 1 Yan D, Chen S, Krauss DJ, Chen PY, Chinnaiyan P, Wilson GD. Tumor Voxel Dose-Response Matrix and Dose Prescription Function Derived Using 18 F-FDG PET/CT Images for Adaptive Dose Painting by Number. Int J Radiat Oncol Biol Phys. 2019 May 1;104(1):207-218. 2 Ding X, Li X, Zhang JM, Kabolizadeh P, Stevens C, Yan D. Spot-Scanning Proton Arc (SPArc) Therapy: The First Robust and Delivery-Efficient Spot-Scanning Proton Arc Therapy. Int J Radiat Oncol Biol Phys. 2016 Dec 1;96(5):1107-1116.

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Digital Poster Development of an extended microdosimetric kinetic model for improved prediction of cell survival fraction in high-dose scenarios Tae ho Jang 1 , Eun Taek Yoon 1 , Hyung Jin Choun 1 , Sung Hyun Lee 2 , Jaeman Son 3 , Hyeongmin Jin 3 , Jong Min Park 4,3,5 1 Interdisciplinary Program, Bioengineering Major, Graduate School, Seoul National University, Seoul, Korea, Republic of. 2 Project Group of the Gijang Heavy Ion Medical Accelerator, Seoul National University Hospital, Seoul, Korea, Republic of. 3 Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea, Republic of. 4 Biomedical Research Institute, Seoul National University Hospital, Seoul, Korea, Republic of. 5 Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Korea, Republic of hypofractionated treatments. 1 Existing microdosimetric kinetic (MK) models are effective in low-dose regions but show significant limitations in high-LET and high-dose conditions. 2 These limitations stem from the reliance of most MK models on low-dose conditions, where the linear coefficient is derived through a Taylor expansion, and the quadratic coefficient (beta) is treated as a constant. 3 We developed an extended MK (eMK) model by expanding the Taylor series to include a variable quadratic coefficient, treating beta dynamically. Our goal was to determine whether the eMK model provides more accurate predictions of cell survival fractions across a broad LET and dose range compared to conventional MK models. Material/Methods: The modified MK (mMK) model 4 was selected for comparison, and the eMK model was similarly developed based on the track structure model 5, 6, 7 . However, unlike mMK, the eMK model incorporates a Taylor expansion of the non Poisson MK model by Hawkins 8 , approximating the equation to include the variable quadratic term. The coefficient Purpose/Objective: Accurate prediction of cell survival fractions is essential for ion beam therapy, especially in high-dose