Inactivation and Mutation Induction in V79 Cells by Low Energy Protons: Re-evaluation of the Results at the LNL Facility

Abstract

During the upgrading of the radiobiological facility at the Laboratori Nazionali di Legnaro (LNL) we found that uncorrected values of the proton energy were used in the past. This circumstance prompted us to perform the re-evaluation of the physical parameters for all the proton beams used in our previous radiobiological investigations (Belli et al. 1987) and, subsequently, the re-evaluation of all our previous dose-response curves for inactivation and mutation induction (Belli et al. 1989, 1991). This re-evaluation leads to significant changes in the dose-response curves and in the RBE-LET relationships only at the two lowest energies (highest LET) used. These two points are not reliable for the identification of a peak in RBE-LET relationship for cell inactivation. In spite of that, the extent of the changes is not such as to modify the general conclusion previously drawn, pointing out that there is a LET range where protons are more effective than alpha-particles.

Applications of amorphous track models in radiation biology

“…Comparisons of calculation [51] to experiments [43][44][45][46] for HPRT mutation in V79 cells are shown in Fig. 3b.…”

“…In Fig. 3a, calculations with the IGK model are compared to data [43][44][45][46] for V79 inactivation. The parameters used for inactivation of V79 cells are shown where m=3, D 0 =1.8 Gy, σ 0 =43 µm 2 , and a 0 =1.1 µm.…”

“…3b. The data are from Belli et al [43] for protons and helium ions, Thacker et al [44] for B ions, and Kiefer and co-workers [45,46] for other heavy ions. A prediction of the model is that a depletion of the mutation cross-section occurs at energies where the inactivation cross-section is a maximum.…”

Radial distribution of electron spectra from high-energy ions

“…The present model offers an efficient method to model such effects. Differences in biological response have been seen between hydrogen and helium ions at the same LET [27,28] and with low-energy heavy ions [29,30], but useful comparisons of fast and slow ions have not been made. For estimating the risk to astronauts from space radiation, differences in radiation quality for ions with the same LET may have important implications.…”

The calculation of radial dose from heavy ions: predictions of biological action cross sections

“…The results of such a calculation are shown in Fig. 6 , compared to data for HGPRT mutations in V79 cells [22,23]. A more detailed description of this calculation will be published elsewhere.…”