ESTRO 2025 - Abstract Book

S2820

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2025

In vivo dosimetry was assessed during the first fraction using SunCheck. Gamma analysis (3%/3 mm) was applied with a 10% threshold for both portal dosimetry (2D) and 3D dosimetry of the PTV. IGRT displacements were analyzed. Results: IGRT displacements were within acceptable limits (Table 1). Portal dosimetry gamma analysis yielded a mean compliance of 86 ± 14%, with a maximum of 98.3 ± 1.7%. 3D gamma analysis for the PTV showed compliance of 88 ± 12%. CARMEN MC TPS revealed absolute dose differences of ~25% (figure 1) compared to CCC, consistent with reported literature.

Conclusion: Advancing toward full Monte Carlo calculations will improve dosimetry for Island Tumors. The use of a 30 mm sphere enhances treatment robustness, providing acceptable in vivo dosimetry and minimizing risks. Keywords: Island Tumor, Full Monte Carlo, TPS References: 1. Louie AV et al. Stereotactic ablative radiation therapy for subcentimeter lung tumors: clinical, dosimetric, and image guidance considerations. Int J Radiat Oncol Biol Phys. 2014 Nov 15;90(4):843-9. 2. Tanguy R et al. Impact of Lack of Coverage Established By Monte Carlo Dose Calculation on Small Island Lung Tumors Treated With Stereotactic Body Radiation Therapy (SBRT). Int J Radiat Oncol Biol Phys. 2015 Nov 1;93(3):E438. 3. Baeza JA et al. SU ‐ E ‐ T ‐ 157: CARMEN MC TPS: A MatLab ‐ Based Research Platform for Monte Carlo Treatment Planning (MCTP) and Customized System for Planning Evaluation. Medical Physics. 2015 Jun;42(6Part14):3367-8.