Does the high pulse dose rate affect the biological efficiency of laser accelerated electrons?


Does the high pulse dose rate affect the biological efficiency of laser accelerated electrons?

Beyreuther, E.; Karsch, L.; Laschinsky, L.; Leßmann, E.; Naumburger, D.; Richter, C.; Pawelke, J.

In recent years, the technology of laser-based particle acceleration was rapidly developed promising compact and potentially more cost-effective accelerators for medical applications, especially for hadron therapy. Beside specific physical requirements, e.g. stability and reliability of the particle beam as well as sufficient particle intensities, these ultra-short pulsed particle beams have to be investigated with regard to their radiobiological characteristics.
As a first step, in vitro cell irradiation experiments were performed using laser accelerated electron beams generated at the Jena Titanium:Sapphire laser system (JETI). Two biological endpoints, the clonogenic survival and remaining DNA double-strand breaks, were analyzed revealing in general a lower biological effectiveness for laser accelerated electrons relative to the continuous 200 kV X-ray reference source. Possible reasons might be the low mean and ultra-high pulse dose rate as well as the different electron spectra delivered to the cells.
The influence of the ultra-high pulse dose rate was assessed using pulsed electrons produced by the electron accelerator ELBE (Electron Linac for beams with high Brilliance and low Emittance) at the Forschungszentrum Dresden-Rossendorf. Based on a superconducting linear accelerator ELBE provides monoenergetic electrons of 20 MeV with a micropulse repetition rate of 13 MHz, a variable time structure that allows for single pulse or continuous irradiations and pulse doses tuneable over more than six orders of magnitude. Consequently, the ELBE beam can be used to mimic laser accelerated ultra-short pulses or for a continuous electron beam generated in a conventional radiotherapy linac.
Both pulse regimes were applied in the present study in order to investigate the influence of the pulse dose rate on the biological effectiveness independent on electron spectra, irradiation setup and dosimetry approach. The biological endpoints assessed at the JETI experiments were also analysed in two normal human cell lines (fibroblast, epithelial). In parallel, the clonogenic survival and DNA double-strand breaks remaining 24 hours post irradiation were also determined at the 200 kV X-ray reference source. To sum up the preliminary results, no significant differences were found for the biological effectiveness of continuous and ultra-short pulsed ELBE electrons relative to 200 kV X-rays. Further results and possible explanations will be discussed.
This work has been supported by the German Federal Ministry of Education and Research (BMBF) under contract 03ZIK445.

  • Lecture (Conference)
    37th Annual Meeting of the European Radiation Research Society, 26.08.-29.09.2009, Prague, Tschechische Republik

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Publ.-Id: 13176