ESTRO 2024 - Abstract Book

S3278

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

Keywords: In vivo dosimetry, gafchromic, dose verification

1679

Proffered Paper

Multicenter investigation of 2D luminescence dosimetry for UHDR electron beams.

Verdi Vanreusel 1,2 , Sophie Heinrich 3 , Thomas De Kerf 4 , Paul Leblans 5 , Dirk Vandenbroucke 5 , Steve Vanlanduit 4 , Dirk Verellen 2,6 , Alessia Gasparini 2,6 , Luana de Freitas Nascimento 1 1 SCK CEN, RDA, Mol, Belgium. 2 University of Antwerp, AReRO, Wilrijk, Belgium. 3 Institut Curie, Inserm U 1021-CNRS UMR 3347, University Paris-Saclay, PSL Research University, Paris, France. 4 University of Antwerp, InViLab, Antwerp, Belgium. 5 Agfa N.V., Innovation office, Mortsel, Belgium. 6 Iridium Netwerk, Department of Medical Physics, Wilrijk, Belgium

Purpose/Objective:

FLASH radiotherapy is a promising new treatment technique in which the therapeutic window is increased by exploiting radiobiological mechanisms [1]. Ultra-high dose rate (UHDR) irradiations result in a reduction of the normal tissue toxicity compared to conventional dose rates. However, UHDR dosimetry is needed to understand and implement FLASH radiotherapy in the clinic [2] . Especially real-time and 2D UHDR dosimetry, useful for monitoring and QA, are missing. The aim of this work is to test the 2D characteristics and dose rate dependence for a passive- and real time dosimeter in an UHDR electron beam. In addition, the energy dependence and individual pulse measurements of the latter are checked.

Material/Methods:

A nanocrystal BaF(Br,I):Eu 2+ coating, as optically stimulated luminescence (OSL) sheet, in combination with a CR-15 (Agfa N.V., Mortsel, Belgium) scanner for readout, is proposed as passive dosimetry system. The real-time dosimetry system consists of a Y 3 Al 5 O 12 :Ce 3+ coating and a scientific CMOS-based camera. Irradiations were performed with the ElectronFlash (SIT, Italy) system at the University of Antwerp (Belgium) and at Institut Curie (France). This allowed UHDR irradiations with nominal energies of 7 and 9 MeV, and 5 and 7 MeV for Antwerp and Orsay, respectively. The dose rate was varied by variation of the pulse length (0 - 4 µs) and pulse repetition frequency (PRF) (1 - 300 Hz) for the 9 and 5 MeV beams in the respective centers. The 2D performance was investigated using the in-vivo applicator with a diameter of 1.8 cm. The dose rate and energy dependence study used the in-vitro applicator with a diameter of 12 cm. Radiochromic film was used as reference dosimeter and a point scintillator was used in Orsay to correct for missed pulses in the absence of triggered acquisition of the camera. The dosimeters were positioned at the surface of an RW3 and PMMA phantom with at least 5 cm water equivalent backscatter in Antwerp and Orsay, respectively. The point scintillator was taped to the applicator of the system. The response of the dosimeters was defined as the