Backscatter radiation at tissue-titanium interfaces

We have made comparisons of cell survival after irradiation of two types of cultured cells grown directly on titanium metal and on plastic control supports. The cell cultures were irradiated with either 6o Co photons or range modulated protons. No significant differences in the colony-forming capacity were found between the irradiated cells grown on titanium and those grown on plastic control supports. This was the case for both radiation types and the results were also observed to be dose-independent. The only observed phenomena were that the two cell-lines differed in radiosensitivity and that protons gave higher biological effects than gamma radiation. The results show that there were no significant changes in cell survival at the interface between the tissue equivalent medium and titanium support indicating that a dose increase induced by backscatter radiation is minimal when high energy photons or range modulated protons are applied. (orig.)