Ponente
Descripción
Purpose: The dose per fraction, the dose rate and the delivery time in radiation therapy are key parameters to understand both the efficacy of the treatment and the level of radiation toxicity in normal tissue. Laser-driven sources are known for their brightness and short pulse duration, and these characteristics offer the possibility to study the biological effects of pulsed radiation beams operating at peak dose rates that are orders of magnitude larger than those achieved in conventional accelerators. Given that these sources can reach a certain dose per pulse, the FLASH effect could be potentially triggered. In this work we investigate the response of in vitro cell cultures to laser-driven, low-energy protons.
Materials and Methods: A set of 27 in vitro A549 cell cultures has been irradiated with low energy protons driven by the VEGA-3 laser beamline available at the Spanish Pulsed Laser Center. The cells were grown in a sterile flask sealed with a thin polyethylene window to reduce energy attenuation. The laser pulses (27 J, 200 fs) were focused onto thin aluminum foils installed on a multishot target system developed at the University of Santiago de Compostela. Since the resulting proton spectrum has a Maxwellian-like broad distribution, a magnetic energy selector was developed to obtain quasi-monoenergetic proton beamlets. These beams were driven in air through a thin Kapton window, and the proton spectrum was characterised using a Thomson parabola and a TOF detector. The dose delivered to the cells was evaluated with unlaminated RCF.
Results: The selected proton energy for cell irradiation was 5 MeV. The preliminary results of the dose evaluation show an average dose per pulse of 100 mGy, with low shot-to-shot variability. Cells were irradiated at 3, 5 and 8 Gy in duplicate to perform radiobiological studies evaluating cell proliferation and clonogenicity. Despite inconclusive findings from the cell proliferation curves, the colony formation assays exhibited a pronounced exponential decrease in cell survival fraction correlated with the administered dose. These findings will be compared with those achieved in a similar experiment performed with laser-driven x-rays, and with a conventional MV Linac.
Conclusions: We have tested the feasibility of cell proliferation and colony formation assays with in vitro cell cultures using laser-driven protons in an experimental campaign which, on a national level, has been the first one combining laser-driven ion sources with biological research.
