Ultra-high-dose-rate FLASH radiotherapy is one of the most promising innovations of the last decade in radiation oncology. It has the potential to eradicate radioresistant tumours and reduce unwanted side effects, that in turn increases cure rates and improves patient quality of life. However, dosimetry infrastructure is lagging behind this clinical and technological advance, with current dosimeters no longer suitable and none of those under development achieving consensus.
The optically read dosimetric gel developed at LNHB-MD (CEA Paris-Saclay) is a promising candidate, as photon beam measurements have shown a linear response over a wide dose range (0.25 - 10 Gy) as well as independence in energy (6 - 20 MV) and dose rate (1 - 6 Gy/min). In addition, this water-equivalent dosimeter has the unique ability to provide three-dimensional measurements with high spatial resolution (< 1 mm) with an associated combined uncertainty of approximately 2% (k = 1). This dosimetry method has been validated for quality control of conventional radiotherapy treatment plans but has never been tested with FLASH beams.
This doctoral project aims to develop a 3D gel dosimetry method suitable for FLASH radiotherapy delivered by charged particle beams: (1) conventional energy electrons (= 10 MeV), (2) very high energy electrons (VHEE = 50 MeV), and (3) protons (= 100 MeV). For each of these types of beams, available at the Institut Curie in Orsay and also at Gustave Roussy in Villejuif, the validation of the dose distribution measured by gel will be carried out by comparison with measurements using other dosimeters (e.g. diamond, alanine) and Monte Carlo simulations.
This study will make a significant contribution to improving patient safety, optimising treatment efficacy and the future integration of FLASH radiotherapy into clinical practice.