Systematic in vitro cell experiments with laser accelerated electron beams


Systematic in vitro cell experiments with laser accelerated electron beams

Laschinsky, L.; Beyreuther, E.; Enghardt, W.; Karsch, L.; Leßmann, E.; Kaluza, M.; Naumburger, D.; Nicolai, M.; Pawelke, J.; Richter, C.; Sauerbrey, R.; Schlenvoigt, H.-P.; Baumann, M.

Purpose: The novel technology of particle acceleration based on high intensity laser systems promises ion radiotherapy accelerators of compact size and reasonable costs. Laser acceleration results in ultra-short pulsed particle beams with very high pulse dose-rate and is used in single shot physics experiments so far. Such particle beams have to be characterized in terms of their radiobiological properties and dosimetric detection and must allow a stable and reliable dose delivery before a conceivable clinical application. In a first step, systematic in vitro cell irradiations with laser accelerated electron beams were performed and dose-effect-curves were obtained.

Material: Experiments have been performed at the Jena Titanium:Sapphire (JeTi) 10 terawatt laser system. Laser pulses (80 fs duration) were focused into a helium gas jet, accelerating electrons to energies of up to 20 MeV. Before cell irradiation, the JeTi system was optimized, adjusting the electron energy and beam spot size and improving the dose rate and homogeneity. Cell irradiations were realized for two squamous cell carcinoma (FaDu, SKX) and two normal tissue (184A1, HSF2) cell lines in a dose range from 0.3 Gy to 10 Gy. For irradiation control a Roos ionization chamber and a Faraday Cup monitored the beam providing on-line dose information. Additional Gafchromic EBT radiochromic films were used for retrospective exact dose determination at the cell site. Referring to irradiation the survival fraction was determined and furthermore DNA double strand breaks were analyzed by immunochemical detection of the co-localized γH2AX and 53BP1 molecules 24 h after irradiation. A conventional X-ray tube (200 kV) was used for reference irradiation.

Results: The JeTi laser accelerator was successfully customized for long-time irradiation of cell samples with prescribed doses. Samples were irradiated at 13 experiment days over a period of 3 months. A reasonably stable and reproducible beam was achieved. Dose homogeneity was examined for all samples inside the target area and the inhomogeneity obtained was less than 10 % for all days and all applied doses. The determined dose-effect-curves show in general a reduced biological effectiveness for the laser accelerated electron beams in comparison with conventional X-rays. The effect of the high pulse dose-rate among the possible reasons will be discussed.

Conclusion: Further experiments are prepared at a 100 terawatt laser system, which will provide laser accelerated proton beams for cell irradiation studies.

This work was supported by the BMBF, grant no. 03ZIK445

  • Lecture (Conference)
    10th BIENNIAL ESTRO CONFERENCE ON PHYSICS AND RADIATION TECHNOLOGY FOR CLINICAL RADIOTHERAPY, 30.08.-03.09.2009, Maastricht, Netherlands
  • Contribution to proceedings
    10th BIENNIAL ESTRO CONFERENCE ON PHYSICS AND RADIATION TECHNOLOGY FOR CLINICAL RADIOTHERAPY, 30.08.-03.09.2009, Maastricht, Netherlands
    Radiother. Oncol. 92 (Suppl. 1)(2009) S89

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Publ.-Id: 13174