Speaker
Dr
Anna Friedl
(University of Munich, Department of Radiation Oncology)
Description
Radiotherapy using charged particles has attracted increasing interest. The superior dose distribution of protons and heavy ions is hoped to translate into excellent dose conformation to the target and sparing of normal tissues. Whether the potential improvements in outcome justify the costs of particle therapy is, however, heavily discussed. The high costs are mainly due to the higher expenses for ion generation, acceleration and beam lines. With the advent of ultrafast high energy lasers, the idea of laser-driven acceleration of particles suitable for therapeutic applications has arisen, combined with the hope for a reduction of costs and required space. The energies achieved at present are still far from those required for radiation therapy. In addition, many technical questions regarding for example energy selection, repetition rate and beam preparation and transport remain unsolved. Apart from these technological developments, it is important to address potential differences in the radiobiological effects between laser-accelerated particles and those accelerated conventionally. Particle beams delivered from laser acceleration will be pulsed. In radiotherapy settings, ultra high dose rates of >109 Gy s-1 are expected at the tumor voxels. Within the Munich-Centre for Advanced Photonics (MAP) we performed a series of systematic comparisons of biological endpoints after irradiation with pulsed and continuous proton beams. We established a pulsed proton beam at the ion microbeam SNAKE at the Munich tandem accelerator to apply macroscopic doses of a few Gy within <1 ns. The irradiations are performed with monoenergetic protons which enables us to perform irradiations with conventional dose rates for direct comparison with the same beam quality. At the dose rates investigated, the RBE of the pulsed and the continuous irradiation mode did not differ significantly for a variety of endpoints such as colony forming ability, induction of chromosomal damage, alteration of cell cycle distribution, and others. Very recently, by combining advanced acceleration and beam transport strategies we were able to generate nanosecond quasi-monoenergetic proton pulses with a table-top laser system, delivering high doses of several Gy to human tumor cells in a single shot. Preliminary measurements of gamma-H2AX foci were in agreement with other proton RBE values in conventional beams at comparable proton energies.
Primary author
Dr
Anna Friedl
(University of Munich, Department of Radiation Oncology)
