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00925njm 22002777a 4500 dc España Palomares, Samuel author Sánchez Parcerisa, Daniel author Ibáñez García, Paula Beatriz author Sánchez Tembleque Verbo, Víctor author Udías Moinelo, José Manuel author Valladolid Onecha, Víctor author Gutiérrez Uzquiza, Álvaro author Bäcker, Claus Maximilian author Bäumer, Christian author Herrmann, Ken author Fragoso Costa, Pedro author Timmermann, Beate author Fraile Prieto, Luis Mario author 2021-02-08 We propose the use of O-enriched water as a suitable contrast agent for potential in-vivo range verification in proton therapy. The low energy production threshold of 18F (2.6 MeV, proton range in water of 115 μm) leads to tissue activation in very close proximity to the maximum dose deposition, facilitating accurate range verification with off-line PET imaging. This idea has been explored in a phantom experiment. A 3D-printed phantom containing inserts with 18Oenriched water was irradiated with a 100-MeV, 8 × 8 cm2 proton beam, and the induced activity was measured with a small-animal PET-CT 30 min after irradiation. The images obtained were compared against Monte Carlo simulation using TOPAS. Good agreement was observed between reconstructed and simulated activity profiles (within 40% for specific 18F activity), with excellent spatial match to the simulated dose deposition. Because of the long half-life of 18F, the specific activity of the contrast agent could be separated and was clearly observed for more than 2 h after irradiation. Activity distribution maps were used to determine the position of the Bragg peak within 2 mm for three different regions of interest. These results show the potential of 18O-enriched water as a contrast agent in proton therapy. España Palomares, S., Sánchez Parcerisa, D., Ibáñez García, P. B. et al. «Direct Proton Range Verification Using Oxygen-18 Enriched Water as a Contrast Agent». Radiation Physics and Chemistry, vol. 182, mayo de 2021, p. 109385. DOI.org (Crossref), https://doi.org/10.1016/j.radphyschem.2021.109385. 0969-806X 10.1016/j.radphyschem.2021.109385 https://hdl.handle.net/20.500.14352/6831 https://doi.org/10.1016/j.radphyschem.2021.109385 Direct proton range verification using oxygen-18 enriched water as a contrast agent