S1840
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
functional structure, maximum (Dmax) and mean (Dmean) doses were extracted; for small-volume structures (< 0.5 cc), only Dmax was considered representative. The relative dose variation ( Δ D) between TPCL and TPFG was calculated as the percentage of the TPCL dose, with negative values indicating dose reduction. Statistical significance of Δ D was evaluated using the Wilcoxon signed-rank test. Results: Across the cohort, 29 regions occurred within 3 cm of the PTV. The number of regions per patient varied by target location and laterality. For all functional regions, both Δ Dmax and Δ Dmean differed significantly from zero (p < 0.001). Functions-guided optimization led to a mean Δ Dmean of -28.4% across functional regions without compromising target coverage or OAR constraints. The largest dose Δ D reductions (>30%) were observed for thalamus, central sulcus, dentate nucleus, globus pallidus, pons, and caudate. For small- volumes structures TPFG achieved a mean Δ Dmax decrease of 33.3%, with several subcortical nuclei showing even greater reductions. Representative functional area dose reductions are summarized in Table 1.
agreement. Conclusion: SFRT GRID plans using simple MLC patterns show promising dosimetric features for clinical implementation on current systems. Keywords: SFRT, GRID Digital Poster Highlight 1495 Integrating functional brain regions into treatment optimization: a multi-institutional dosimetric study in CyberKnife SRT for brain metastases Feng Yang 1 , Tiziana Malatesta 2 , Lucia Clara Orlandini 1 , Federica Murtas 2 , Gang Yin 1,3 , Federica Pavoncello 2 , Xianliang Wang 1 , Peng Xu 1 , Xin Xin 1 , Bin Tang 1 , Xiongfei Liao 1 , Jie Li 1 , Francesco Miccichè 2 , Silvia Chiesa 4 , Vincenzo Valentini 2 1 Radiation Oncology, Sichuan Cancer Hospital & Research Institute University of Electronic Science and Technology of China, Chengdu, China. 2 Radiotherapy and Medical Oncology and Radiology, Isola Tiberina – Gemelli Isola Hospital, Rome, Italy. 3 Oncology Department, Panzhihua Central Hospital, Panzhihua, China. 4 Department of Diagnostic Imaging, Radiation Oncology and Hematology, Fondazione Policlinico Universitario A. Gemelli, IRCCS, Rome, Italy Purpose/Objective: Preserving brain function has become an emerging goal in stereotactic radiotherapy, with increasing attention to the impact of radiation dose on functional brain regions. This study investigated whether including these regions as optimization objectives during SRT for brain metastases could achieve measurable dose reduction. Material/Methods: A retrospective analysis was conducted on 41 patients with single brain metastases treated with SRT using CyberKnife system in two institutions. Treatment doses were 22 Gy in a single fraction or 30 Gy in three fractions, according to lesion size and location. For each patient the clinical plan (TPCL) was generated according to international recommendations for target coverage and OAR constraints [1-3]. Functional region auto-segmentation was performed with the Brainlab platform using multiple MRI sequences (T1-weighted, T2-weighted, and/or FLAIR images). Functional regions within 3 cm of the PTV were imported into the clinical plan to evaluate received doses. A second plan, the function-guided plan (TPFG), was optimized following the same guidelines but incorporating surrounding functional regions as avoidance structures. Target coverage and standard OAR indices were required to remain unchanged between TPCL and TPFG. For each
Conclusion: Including functional neuroanatomical structures in the optimization process allowed a significant, systematic dose reduction while maintaining plan quality. Although these regions lack defined clinical relevance or dose tolerance thresholds, this preliminary work demonstrates the feasibility of integrating functional anatomy into SRT planning. Such an approach may support the development of function-sparing radiotherapy, warranting further clinical and neurocognitive validation. References: 1. Benedict SH, Yenice KM, Followill D, Galvin JM, Hinson W, Kavanagh B: Stereotactic body radiation therapy: The report of AAPM Task Group 101. Medical Physics 2010, 37(8):4078-4101.2. Timmerman R: A Story of Hypofractionation and the Table on the Wall. International Journal of Radiation Oncology Biology and Physics 2022, 112(1):4-21.3. Gondi V, Bauman G,
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