S2798
RTT - RTT contouring, target definition, and treatment planning
ESTRO 2026
Digital Poster 4190 A Visualized Thermosensitive Color-changing Personalized Bolus for Post-mastectomy Radiotherapy: A Feasibility Study on Dosimetry and Skin Toxicity Peifeng Zhao, Min Han, Yong Wang, Yanze Sun, Ye Tian Radiotherapy & Oncology, The General Hospital of Nuclear Industry, Soochow, China Purpose/Objective: This study focuses on evaluating the application of the visualized thermosensitive personalized bolus in PMRT. By comparing its performance with that of commercial boluses, this study focuses on evaluating differences in dosimetric outcomes and skin toxicity responses. Through this comparative analysis, we aim to validate the feasibility and clinical utility of the visualized thermosensitive color-changing personalized bolus as an innovative tool in enhancing treatment accuracy and patient outcomes. Material/Methods: Forty PMRT patients (June 2023–June 2024) were randomized into two groups. Group A (experimental group, 20 patients) underwent two CT scans: A1 (without bolus) and A2 (with the visualized thermosensitive color-changing personalized bolus), followed by treatment with the thermosensitive color- changing personalized bolus. Group B (control group, 20 patients) also underwent two CT scans: B1 (without bolus) and B2 (with a conventional commercial bolus), followed by treatment with the commercial bolus. Treatment plans were generated for virtual bolus (A1- Plan, B1-Plan) and real bolus (A2-Plan, B2-Plan). A3- Plan (A1-Plan applied to thermosensitive bolus treatment) and B2-Plan (B1-Plan applied to commercial bolus treatment) were compared to evaluate dosimetric differences in target volumes and organs at risk (OARs). In addition, skin toxicity grades were also recorded in order to assess safety of the thermosensitive bolus. Results: In Group A, A1-Plan and A2-Plan showed no significant differences in OAR doses (e.g., ipsilateral lung, heart, contralateral breast, skin Dmax/Dmean) or target metrics (V50Gy, Dmax, homogeneity index (HI), conformity index (CI), monitor units (MU)). A3-Plan compared to A1-Plan had minor differences in target coverage (94.05% vs. 95.14%), HI (0.148 vs. 0.147), and CI (0.83 vs. 0.84). In Group B, B2-Plan had significantly reduced target coverage (89.9% vs. 95%), homogeneity (0.153 vs. 0.136), and conformity (0.817 vs. 0.810) compared to B1-Plan, attributed to air gaps from the commercial bolus. The thermosensitive color-changing personalized bolus had better skin adherence, significantly reduced air cavity volumes (3833 mm ³ vs.
Total MU increased with arc number: with mean values of 2,847 MU (2 arcs), 3,068 MU (3 arcs) and 3,343 MU (4 arcs) (Figure 2).Irradiation time also increased: with mean values of 2.3 min (2 arcs), 2.8 min (3 arcs) and 2.9 min (4 arcs) (Figure 2).
Conclusion: Increasing the number of arcs did not result in significant dosimetric improvement of lung SBRT plans. The best conformity was achieved with 3 arcs (though differences were not significant), providing an optimal balance between dose distribution and treatment efficiency. Dose to OAR remained largely independent of arc number, mainly influenced by PTV location. Although irradiation time increased with more arcs, the difference between 3- and 4-arc plans was minimal.Plans using 3 arcs demonstrated the best balance between dosimetric quality and efficiency, without substantially prolonging treatment time. References: Darréon J, Debnath SBC, Benkreira M, Fau P, Mailleux H, Ferré M, Benkemouche A, Tallet A, Annede P, Petit C, Salem N. A novel lung SBRT treatment planning: Inverse VMAT plan with leaf motion limitation to ensure the irradiation reproducibility of a moving target. Med Dosim. 2024 Summer;49(2):159-164. doi: 10.1016/j.meddos.2023.11.001. Epub 2023 Dec 6. PMID: 38061915.Pokhrel D, Halfman M, Sanford L. FFF- VMAT for SBRT of lung lesions: Improves dose coverage at tumor-lung interface compared to flattened beams. J Appl Clin Med Phys. 2020 Jan;21(1):26-35. doi: 10.1002/acm2.12764. Epub 2019 Dec 20. PMID: 31859456; PMCID: PMC6964748. Keywords: Lung, SBRT, VMAT
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