Biophysical Studies with High-Energy Argon Ions 2. Determinations of the Relative Biological Effectiveness, the Oxygen Enhancement Ratio, and the Cell Cycle Response

Publisher Website
Google Scholar
Abstract
Chinese hamster cells cultured in vitro were used as a test system to investigate the radiobiological effects of 429 MeV/amu [atomic mass unit] Ar ions. Samples were irradiated at 4 positions in the depth dose profile. The 1st was located on the entrance plateau, the 2nd on the ascending portion of the depth dose curve upstream from the Bragg peak, the 3rd as close as possible to the Bragg peak and the 4th on the tail beyond the peak. For a surviving fraction of 0.1, the relative biological effectiveness was about 2.4 for the plateau, ascending region and tail of the depth dose curve and had a lower value of about 1.5 at the peak. The O2 enhancement ratio was high, in excess of 2 in the incident plateau and fell to about 1.3 close to the Bragg peak. Cells were irradiated with X-rays or Bragg-peak Ar ions at various times after synchronization with hydroxyurea. A 17-fold variation in survival through the cycle with X-rays was reduced to a 2-fold variation with Ar ions.