ESTRO 2025 - Abstract Book

S2659

Physics - Detectors, dose measurement and phantoms

ESTRO 2025

Conclusion: This study demonstrates a first step for a standardized workflow to quantify and select tissue-equivalent filaments to create more-realistic phantoms that can be tailored to fit clinical CT-calibration curves, follow the exact clinical workflow and lead to more patient-specific phantoms, aiding adaptive radiotherapy quality.

Keywords: 3D-printing, Anthropomorphic phantoms, CT Imaging

References: 1. Hünemohr N, Krauss B, Tremmel C, Ackermann B, Jäkel O, Greilich S. Experimental verification of ion stopping power prediction from dual energy CT data in tissue surrogates. Phys Med Biol 2014;59:83–96

3905

Proffered Paper Dose measurements with a portable graphite calorimeter using ultra-high dose rate proton and electron beams for FLASH radiotherapy Giuliana Milluzzo 1 , Graham Bass 2 , Andrea Cavalieri 3 , Maria Grazia Celentano 4,5 , Fabio Di Martino 4,6,5 , Alex Duralis 2 , Stefano Lorentini 7 , Luigi Masturzo 4 , Chinonso Okpuwe 1 , Jake Pensavalle 4 , Severine Rossomme 8 , Emanuele Scifoni 9 , Anna Subiel 2 , Francesco Tommasino 9,10 , Annalisa Trianni 7 , Enrico Verroi 9 , Francesco Romano 1 1 Catania Division, INFN, Catania, Italy. 2 Hampton Road, National Physical Laboratory, Teddington, United Kingdom. 3 Center for Instrument Sharing of the University of Pisa, University of Pisa, Pisa, Italy. 4 Centro Pisano ricerca e implementazione clinica Flash Radiotherapy, (CPFR@CISUP), Pisa, Italy. 5 Pisa Division, INFN, Pisa, Italy. 6 Fisica Sanitaria, , Azienda Ospedaliero Universitaria Pisa AOUP, Pisa, Italy. 7 Protontherapy Department, , Azienda Provinciale per i Servizi Sanitari (APSS), Trento, Italy. 8 R&D PT, IBA Dosimetry, Louvain-la-Neuve, Belgium. 9 Trento Institute for Fundamental Physics and Applications (TIFPA), INFN, Trento, Italy. 10 Department of Physics, University of Trento, Trento, Italy Purpose/Objective: Small portable calorimeters are recently becoming valuable alternative approaches for reference dosimetry in FLASH radiotherapy. A portable secondary standard calorimeter (GCal) was realized at the National Physics Laboratory (NPL, UK) and consists of a central 2 mm thick, 16 mm diameter graphite core connected to a single thermistor and a Whetstone Bridge enabling the measurement of the temperature rise. Material/Methods: Recently, several experimental campaigns have been carried out by the INFN Catania group to characterize the GCal with both ultra-high dose rate (UHDR) electron and proton beams. Specifically, the 228 MeV UHDR proton beams accelerated at the Trento Proton Therapy Center were used to measure the dose to water with the GCal, previously calibrated in terms of absorbed dose-to-water with a 60 Co source at the NPL, by varying the beam current (average dose rate from 10 Gy/s up to 250 Gy/s) and by fixing a dose rate around 150 Gy/s and varying the irradiation time (10 ms-100 ms). The 9 MeV UHDR electron beams accelerated by the Electron FLASH linac at the Centro Pisano for Flash Radiotherapy (CPFR) in Pisa were also used to extend the study of the GCal response to extreme instantaneous dose rate conditions (up to 2 MGy/s). The PPC05 IBA ionization chamber and alanine dosimeters were also used for comparison, while Radiochromic films were employed for dose profile measurements. Results: Fig. 1a shows the temperature rise signals measured by the GCal with the UHDR proton beams keeping a constant beam dose rate of 150 Gy/s and varying the irradiation time from 10 ms up to 100 ms. A very small variation within +-1% in the measured absorbed dose to water with the GCal by varying the average dose rate can be also observed in Fig. 1b. On the other hand, Fig. 2 shows the percentage deph dose (PDD) distribution of the 9 MeV UHDR electron beams measured with the GCal and compared with the one measured with the flash diamond (fd) detector supplied