Direct proton range verification using oxygen-18 enriched water as a contrast agent. (May 2021)

• Record Type: Journal Article
• Authors: España, Samuel; Sánchez-Parcerisa, Daniel; Ibáñez, Paula; Sánchez-Tembleque, Víctor; Udías, Jose Manuel; Onecha, Víctor V.; Gutierrez-Uzquiza, Alvaro; Bäcker, Claus Maximilian; Bäumer, Christian; Herrmann, Ken; Fragoso Costa, Pedro; Timmermann, Beate; Fraile, Luis Mario
• Is Part Of: Radiation physics and chemistry. Volume 182(2021)
• Publication Date: 2021-05
• Subjects: 18O -- Phantom -- Activation -- Range verification -- Protontherapy; Radiation chemistry -- Periodicals; Radiometry -- Periodicals; Radiation -- Periodicals; Chimie sous rayonnement -- Périodiques; 539.2
• DOI: 10.1016/j.radphyschem.2021.109385
• Languages: English
• ISSNs: 0969-806X

Abstract

Abstract: We propose the use of 18 O-enriched water as a suitable contrast agent for potential in-vivo range verification in proton therapy. The low energy production threshold of 18 F (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 18 O-enriched water was irradiated with a 100-MeV, 8 × 8 cm 2 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 18 F activity), with excellent spatial match to the simulated dose deposition. Because of the long half-life of 18 F, 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 18 O-enriched water as a contrast agent in proton therapy. Highlights: 18O could be used as a contrast agent for proton therapy range verification. Phantom with 18O enriched water was irradiated 100-MeV protons and imaged with PET. 18O induced PET activity was observed for more than 2 h after irradiation. Observed PET activity agreed with predictions from Monte Carlo TOPAS. Activity distribution maps allowed us to locate Bragg peak position within 2 mm.