ESTRO 2025 - Abstract Book

S2619

Physics - Detectors, dose measurement and phantoms

ESTRO 2025

12000XL, Epson). Using the image analysis software Hero 2024.2.0 (Hero Imaging AB) each film was registered to the treatment plan and normalized to the mean dose in the corresponding slice. LET sensitivity of the film was corrected for using LET distributions calculated in the in-house Monte Carlo software AutoMC. To compare the doses, gamma analysis was performed.

Figure 1. 3D-printed skull in sections with inserted double-layered Gafchromic film.

Results: The mean gamma pass rate (3%/3mm) was 90.9% [range: 76.0-98.3%] for all six slices including repeated measurements and scans, double-layer film and double calibrations. One example slice (gamma pass rate 96.4%) show that the measured dose is higher than planned in the steep gradient area (Fig 2a-d).

Figure 2. Example slice of hippocampal-sparing CSI proton therapy plan in sagittal view. a) Planned dose distribution, b) measured dose distribution, c) the difference between the planned and measured dose, d) gamma value map.