Search

Recent investigations into radiation-induced side effects have focused on understanding the physiopathological consequences of irradiation on late-responding tissues like the spinal cord, which can lead to chronic progressive myelopathy. Proton therapy, an advanced radiation treatment, aims to minimize damage to healthy tissues through precise dose deposition. However, challenges remain, particularly regarding the variation in dose distribution, characterized by maximum deposition at the end of the proton range, known as the distal fall-off of a spread-out Bragg peak. This variation is critical for nearby organs at risk. In this preliminary study, we evaluated the effects of proton irradiation on the neuronal cell population in mouse spinal cord by comparing two positions of the particle range dose deposition profile. We irradiated the spinal cords at the entrance and the distal edge of the spread-out Bragg peak with a single proton dose. Results showed changes in the expression of synaptophysin, a presynaptic protein crucial for synaptic plasticity. Our findings suggest that examining early radiation-induced physiopathological effects on late-responding tissues can provide valuable insights into neuronal plasticity, informing clinical treatment planning for proton beam positioning., Competing Interests: Declarations. Competing interests: The authors declare no competing interests. Ethical approval: Approval was granted by the Ethics Committee of University of Catania, Catania (Italy), approval Code: 248/2018-PR of 30/03/2018, according to Ministry of Health. All data generated or analysed during this study are included in this published article [and its supplementary information files]., (© 2025. The Author(s).)

Among the most investigated hypotheses for a radiobiological explanation of the mechanism behind the FLASH effect in ultra-high dose rate radiotherapy, intertrack recombination between particle tracks arriving at a close spatiotemporal distance has been suggested. In the present work, we examine these conditions for different beam qualities and energies, defining the limits of both space and time where a non-negligible chemical effect is expected. To this purpose the TRAX-CHEM chemical track structure Monte Carlo code has been extended to handle several particle tracks at the same time, separated by pre-defined spatial and temporal distances. We analyzed the yields of different radicals as compared to the non-interacting track conditions and we evaluated the difference. We find a negligible role of intertrack for spatial distances larger than 1 μm, while for temporal distances up to μs, a non-negligible interaction is observed especially at higher LET. In addition, we emphasize the non-monotonic behavior of some relative yield as a function of the time separation, in particular of H2O2, due to the onset of a different reaction involving solvated electrons besides well-known OH· recombination.