Application tests

Biological effects

            - K.Kirkby, Surrey

Dosimetry tests

            - S. Green, Birmingham

Libra technology has the potential to make a major impact in the medical area, particularly regarding the use of laser- driven ion beams in oncology. In order to evaluate the suitability of these sources for proton and ion beam therapy, we will carry out the first comparative tests of biological effectiveness and dose deposition employing Libra and conventional ion beams (as provided by the Surrey ion beam facility and the NPL beamlines). Cell response to controlled doses of radiation will be studied by irradiation with laser-driven proton beams, suitably energy- selected and collimated. This will be compared to cell response under irradiation, with the same dose and Bragg peak location, by micro- and nano-ion beams. A particular issue is the crucially different duration of laser-driven ion bursts from the pulses used so far in proton and carbon ion therapy, and the effect that ultra-short irradiation with rapidly repeated time gaps may have on quantitative cell survival in cells and tissues. The response of the cells to precisely controlled doses of radiation, at specific parts of their structure and at specific points in the cell cycle, enables the mechanisms by which ion beams interact with isolated living cells to be studied. It also enables comparisons to be made between the interaction of different ion species and the way they interact with chemotherapeutic drugs.

A crucial task in view of future radiotherapy applications will be obtaining accurate, reproducible and appropriate dose deposition by ‘spread out Bragg peaks’ for typical cancer targets exploiting the emittance and spectral characteristics of laser-driven ion beams. This will include detailed inverse Monte Carlo modelling of the dose deposition properties of such beams, the use of suitable human body phantoms and their exposure to laser-driven ion beams with detailed measurements of spatial dose distributions.