Intermediate LET-like effect in distal part of proton Bragg peak revealed by track-ends imaging during super-Fricke radiolysis

Abstract

Upstream of the efficiency of proton or carbon ion beams in cancer therapy, and to optimize hadrontherapy results, we analysed the chemistry of Fricke solutions in track-end of 64-MeV protons and 1.14-GeV carbon ions. An original optical setup is designed to determine the primary track-segment yields along the last millimetres of the ion track with a sub-millimetre resolution. The Fe3+-yield falls in the Bragg peak to (4.9 ± 0.4) × 10–7 mol/J and 1.9 × 10–7 mol/J, under protons and carbon ions respectively. Beyond the Bragg peak, a yield recovery is observed over 1 mm for proton beams. It is attributed to the intermediate-LET of protons in this region where their energy decreases and energy distribution becomes broader, in relation with the longitudinal straggling of the beam. Consequently to this LET decrease in the distal part of the Bragg peak, Fe3+-yield increases. For the first time, this signature is highlighted at the chemical level under proton irradiation. Nevertheless, this phenomenon is not identified for carbon ion beams since their straggling is lower. It would need a greater spatial resolution to be observed.

Condensed Matter Systems Exposed to Radiation: Multiscale Theory, Simulations, and Experiment

“…It has been observed that the results of Geant4-DNA and continuous beam irradiations did not match. 655 The reason for the disagreement is that the chemistry is complex due to the overlapping of the tracks.…”

“…Every parameter that represents the beam reality has to be considered in MM, which is not the case in current simulations. It has been observed that the results of Geant4-DNA and continuous beam irradiations did not match . The reason for the disagreement is that the chemistry is complex due to the overlapping of the tracks.…”