https://doi.org/10.1140/epjs/s11734-026-02248-4
Regular Article
Quantification and analysis of out-of-field dose in radiotherapy for 6 MV and 18 MV beams using Monte Carlo simulation and experimental dosimetry
1
Subatomic Research and Applications Team, Laboratory of the Physics of Condensed Matter (LPMC-ERSA), Faculty of Sciences Ben M’Sick, Hassan II University, Casablanca, Morocco
2
Mohamed VI Center for the Treatment of Cancers of the IBN ROCHD University Hospital Center, Casablanca, Morocco
3
Laboratory of Sciences and Health Technologies, High Institute of Health Sciences (ISSS), Hassan I University, Settat, Morocco
4
Mohamed VI Center for the Treatment of Cancers of the IBN ROCHD University Hospital Center, Faculty of Medicine and Pharmacy, Hassan II University, Casablanca, Morocco
a
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Received:
31
August
2025
Accepted:
3
March
2026
Published online:
13
March
2026
Abstract
Accurate estimation of out-of-field doses in radiotherapy is essential for minimizing healthy tissue exposure and optimizing radioprotection, particularly in pediatric patients. This study aims to quantify and compare out-of-field doses for 6 MV and 18 MV photon beams using Monte Carlo (MC) simulations with GATE, Treatment Planning System (TPS) calculations, and Optically Stimulated Luminescence Dosimetry (OSL). Experiments were conducted on PMMA and pediatric phantoms to evaluate the impact of anatomical characteristics on dose distribution. Dose measurements were performed at 10, 15, 20, 25, and 30 cm from the beam axis for a 10 × 10 cm2 field using the three methods. For the pediatric phantom, dose assessments focused on six critical organs using OSLDs (nanoDots™) and TPS under 3D-CRT and VMAT techniques. For the PMMA phantom, MC estimated higher out-of-field doses than OSL and TPS, particularly near the irradiation field. At 10 cm for 6 MV, the absolute dose differences were 0.20 Gy (MC vs. OSL, 21.98%) and 0.309 Gy (MC vs. TPS, 33.96%), persisting at 30 cm (MC vs. OSL: 23.08%; MC vs. TPS: + 30.77%). For 18 MV, TPS and OSL showed strong agreement (differences < 10%), but MC remained significantly higher (31.31% vs. OSL and 42.86% vs. TPS at 30 cm). For the pediatric phantom, OSL doses were consistently higher than TPS calculated doses across all organs. In 3D-CRT, differences between OSL and TPS were 26.22% (right lung), 29.81% (left lung), 25.57% (left kidney), and 16.62% (right kidney). In VMAT, discrepancies ranged from 7.34% (oesophagus) to 24.96% (right lung). Significant discrepancies in out-of-field dose estimation among MC, TPS, and OSL highlight the limitations of TPS in peripheral dose assessment. Experimental validation remains essential, particularly in pediatric radiotherapy, to refine dose calculation algorithms, enhance treatment planning, and improve radioprotection strategies.
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© The Author(s), under exclusive licence to EDP Sciences, Springer-Verlag GmbH Germany, part of Springer Nature 2026
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
