Laser Particle Acceleration for Radiotherapy: A first radiobiological characterization of laser accelerated electrons

In recent years, the technology of laser-based particle acceleration has developed at such a rate that compact and potentially more cost-effective accelerators are promised for medical application, e.g. for high precision hadron radiotherapy. Necessary requirements are the supply of stable and reliable particle beams with reproducible properties, sufficient particle intensities and monoenergetic spectra. Additionally, a precise dose delivery in an appropriate time and the exposure of a desired irradiation field are needed. Beside these physical demands, the consequences on detection and dosimetry as well as the radiobiological effect on living cells have to be investigated for the ultra-short pulsed laser-based particle beams. As a first step, the laser accelerator facility at the Jena Titanium:Sapphire system was customized for in vitro cell irradiation experiments and the delivered electron beam was im-proved with regard to its spectrum, diameter, dose rate and dose homogeneity. Furthermore, a custom-designed beam and dose monitoring system was established that enables real-time monitoring of the irradiation experiments and a precise determination of the dose delivered to the cells. Moreover, stable and reproducible beam properties were achieved during the whole three month experiment campaign. Dose-effect-curves were obtained for four cell lines and two endpoints, generally displaying a lower biological effectiveness for short-pulsed laser-accelerated electrons relative to the continuous 200 kV X-ray reference irradiation. Possible reasons will be discussed.