Single-pulse Gy-scale irradiation of biological cells at $10^{13}$ Gy/s average dose-rates from a laser-wakefield accelerator

TL;DR

This paper introduces a novel laser-wakefield accelerator capable of delivering ultra-high dose rates of radiation in a single femtosecond pulse, enabling new radiobiological studies and revealing potential differences in cellular responses compared to conventional irradiation methods.

Contribution

The study demonstrates the first experimental setup capable of delivering femtosecond-scale, ultra-high dose-rate radiation, and explores its biological effects on human cells, highlighting potential advantages over traditional methods.

Findings

Achieved dose rates up to 10^13 Gy/s in a single femtosecond pulse.

Observed increased relative biological effectiveness in irradiated cells.

Indications of reduced radioresistance in tumor cells at ultra-high dose rates.

Abstract

We report on the first experimental characterization of a laser-wakefield accelerator able to deliver, in a single pulse, doses in excess of \unit[1]{Gy} on timescales of the order of a hundred femtoseconds, reaching unprecedented average dose-rates up to \unit[10$^{13}$]{Gy/s}. The irradiator is demonstrated to deliver doses tuneable up to \unit[2.2]{Gy} in a cm$^2$ area and with a high degree of longitudinal and transverse uniformity in a single irradiation. In this regime, proof-of-principle irradiation of patient-derived glioblastoma stem-like cells and human skin fibroblast cells show indications of a differential cellular response, when compared to reference irradiations at conventional dose-rates. These include a statistically significant increase in relative biological effectiveness ($1.40\pm0.08$ at 50\% survival for both cell lines) and a significant reduction of the relative radioresistance of tumour cells. Data analysis provides preliminary indications that these effects might not be fully explained by induced oxygen depletion in the cells but may be instead linked to a higher complexity of the damages triggered by the ultra-high density of ionising tracks of femtosecond-scale radiation pulses. These results demonstrate an integrated platform for systematic radiobiological studies at unprecedented beam durations and dose-rates, a unique infrastructure for translational research in radiobiology at the femtosecond scale.