ESTRO 2025 - Abstract Book

S335

Brachytherapy - Physics

ESTRO 2025

Results:

We evaluated protective thicknesses ranging from 2 mm to 14 mm. The addition of protective shielding showed a dose reduction trend across all organs at risk. However, this trend was non-monotonic; for each organ, there was a specific shielding thickness, termed the "optimal thickness" (OT), beyond which dose levels began to rise again. This optimal thickness varied depending on the CTV volume (cc) and followed the fit equation OT = a(Volume) 2 + b(Volume) + c , where parameters a, b, and c were determined based on the relative OAR-CTV positioning, as illustrated in Figure 1. Separate fits were conducted for mean values of eyes and lenses. Conclusion: A comprehensive understanding of optimal implantation techniques and the dose non-uniformity ratio, as discussed in current literature, is essential for minimizing treatment volume-related toxicity. Our findings demonstrate that incorporating eye shielding into clinical practice effectively reduces radiation exposure to critical organs without requiring alterations to existing clinical workflows.

Keywords: Brachytherapy, Nasal Vestibule, Protections

References: [1] Tagliaferri, L.; Fionda, B.; Bussu, F.; Parrilla, C.; Lancellotta, V.; Deodato, F.; Cammelli, S.; Boldrini, L.; Gambacorta, M.A.; Morganti, A.G.; et al. Interventional radiotherapy (brachytherapy) for squamous cell carcinoma of the nasal vestibule: A multidisciplinary systematic review. Eur. J. Dermatol. EJD 2019, 29, 417–421. [2] Beaulieu, L.; Carlsson Tedgren, Å.; Carrier, J.F.; Davis, S.D.; Mourtada, F.; Rivard, M.J.; Thomson, R.M.; Verhaegen, F.;Wareing, T.A.; Williamson, J.F. Report of the Task Group 186 on model-based dose calculation