Ponente
Descripción
Introduction
The practice of radiation oncology has undergone a substantial improvement in all the stages of the radiotherapy process. However, the progress in our understanding of radiobiological processes has fallen behind. Take for instance FLASH therapy, whose underlying biological mechanisms still remain unknown [1]. An improvement of the accuracy, availability, and reproducibility of radiobiology experiments at both conventional and FLASH conditions, would greatly help to fill this gap. X-ray irradiators for preclinical research are becoming increasingly popular in cancer research and specially in radiobiology experiments, representing an alternative to traditional gamma irradiators with several advantages, such as their relative low cost, ease of use, smaller certification/authorization burden, and good control of dose rate [2]. Therefore, a FLASH capable X-ray irradiator would be of interest [3,4].
Materials and methods
In this work, we propose a new concept of small animal X-ray irradiator based on a conventional imaging X-ray tube for preclinical research [5]. We assessed its feasibility to deliver FLASH dose rates. Our design puts the imaging X-ray tube into a shielded cabinet, which makes the system affordable and suitable to use without disruption in existing laboratories and with minimum regulatory burden. Two conventional 150 kVp X-ray tubes were characterized with Gafchromic films for dose rates and dose uniformity. Monte Carlo simulations were also performed to model the irradiator, and the efficiencies of the tube and dose rates (with and without additional filtration) were calculated and compared with measurements. The feasibility of achieving ultra-high dose rates was determined from the rating charts provided by the manufacturer and measurements.
Results
The small animal irradiator proposed in this work was able to deliver conventional dose rate irradiation (0.5-1 Gy/min) at 150 kVp at 20 cm distance with minimum amount of filtration. FLASH irradiations (a 10 Gy dose delivered at >40 Gy/s) were also possible at the maximum capabilities of the tubes by placing the samples at the closest distances from the sources.
Conclusion
An irradiator based on a standard imaging X-ray tube with FLASH dose-rates capabilities for preclinical research is feasible. A prototype has already been built by SEDECAL Molecular Imaging, one of the largest manufacturers of X-ray portable imaging systems worldwide.
[1] Mazal, A., et al. Brit. J. Radiol., 2020, 93, (1107), pp. 20190807
[2] Ghita, M., et al. Cancers, 2019, 11, (2), pp. 170
[3] Cecchi, D.D et al. Med. Phys. 2021, 48, (11), pp. 7399-7409
[4] Rezaee, et al. Phys. Med. Biol., 2021, 66, (9), pp. 095006
[5] Espinosa-Rodríguez et al. Radiat. Phys. Chem., 2023, 206, pp. 110760
