S118
Brachytherapy - Physics
ESTRO 2026
multiple distances relative to the fiber (Figure 1b). Repeated acquisitions were used to evaluate response stability. Bare fibers were also tested to distinguish scintillation signals from Stem-effect contributions, revealing potential radiation-induced fiber damage.
106/Rh-106 applicators with a diamond detector calibrated in a clinical megavoltage electron beam. Phys.Med.Biol. 70: 06NT01, 2025
Digital Poster Highlight 844
Miniaturized fiber-optic dosimeters for in vivo dosimetry in interventional radiotherapy (modern brachytherapy) Elisa Placidi 1 , Enrico Rosa 1,2 , Bruno Fionda 1 , Hiba Al Halaby 3 , Stefano Micco 3 , Patrizio Vaiano 3 , Alberto Micco 3 , Marco Consales 3,4 , Lucia Di Maio 1 , Giorgia Masiello 1 , Ciro Mazzarella 1 , Luca Tagliaferri 1,5 , Andrea Cusano 3,4 , Marco De Spirito 1,6 , Maria Antonietta Gambacorta 1,5 1 Dipartimento di Diagnostica per Immagini e Radioterapia Oncologica, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy. 2 Department of Theoretical and Applied Sciences, eCampus University, Novedrate, Italy. 3 Università degli studi, del Sannio, Benevento, Italy. 4 Centro Regionale Information Communication Technology, Cerict SCRL, Benevento, Italy. 5 Dipartimento di Scienze Radiologiche, Università Cattolica del Sacro Cuore, Rome, Italy. 6 Dipartimento di Neuroscienze, Università Cattolica del Sacro Cuore, Rome, Italy Purpose/Objective: This study, carried out within the framework of the PRIN 2022 “Welcome Project”, aims to characterize the performance of advanced scintillating optical fiber dosimeters for use in brachytherapy treatments employing Pulsed Dose Rate (PDR) and High Dose Rate (HDR) irradiation. The objective is to evaluate their response in terms of dose sensitivity, linearity, repeatability, angular dependence, and signal-to-noise ratio. An additional key objective is to assess the feasibility of integrating these miniaturized dosimeters directly into the catheters or applicator needles used in interventional radiotherapy (modern brachytherapy). In particular, due to their small dimensions, these dosimeters could potentially allow the placement of multiple sensors within a single catheter, enabling real-time multi-point dose verification, a capability not currently available in clinical practice. Material/Methods: Optical fibers with core diameters of 400 µm and 600 µm were coupled with scintillating caps ranging from 118 µm to 1.5 mm. The caps were fabricated using Gadox (Gd2O2S:Tb) mixed in UV curable resin at different weight ratios. For HDR tests, the fiber was positioned parallel to the 192Iridium source at various distances to simulate real dose-monitoring conditions (Figure 1a). For PDR tests, the source was positioned at controlled angular configurations (0°, ±90°) and
Results: Fibers with sub-mm caps exhibited strong linearity with respect to gate time and high signal repeatability, with the measured dose response following an expected 1/r ² dependence (Figure 1a&b)). Even short caps (~0.2 mm) exhibit high signal-to-noise ratios confirming effectiveness of the dosimeter. For 400 µm fibers with a 190 um cap, detectable dose signals were observed with the PDR source up to 30 mm from the source (Figure 1b), demonstrating suitability for miniaturized detector designs. Measurements revealed reduced repeatability in some conditions and indications of possible radiation-induced fiber damage highlighting the need for further stability assessments. Conclusion: Scintillating optical fiber dosimeters show strong potential for real-time in vivo dosimetry in interventional radiotherapy. Their small size enables their integration directly into catheters and needles, and even the possibility of placing multiple dosimeters within a single catheter to achieve multi-point dose
monitoring, representing a significant clinical advancement. Future work will optimize light
collection (e.g., with reflective coatings and metalens structures) and evaluate smaller-core fibers to further support multi-fiber catheter-based dose mapping. Keywords: Brachytherapy, in vivo dosimetry, optic fiber
Poster Discussion 965
Permanent implant prostate brachytherapy 3D dosimetric reference datasets for model-based dose calculations Fatemeh Akbari 1 , Vasiliki Peppa 2 , Samuel Ouellet 3,4 , Narjes Moghadam 1 , Sandra Oliver 5 , Vicent Gimenez- Alventosa 6,7 , Luc Beaulieu 3,4 , Javier Vijande 6,7 , Rowan M Thomson 1
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