Radiobiology of α Particles: III. Cell Inactivation by α-Particle Traversals of the Cell Nucleus

TLDR

Alpha‑particle traversals of the nucleus that fail to kill cells may lead to carcinogenesis. The authors exposed hamster, mouse, and human cell lines to collimated 3.5‑MeV alpha particles, examined multiple parameters, and calculated the energy‑deposition distribution within the nuclei. Lethal lesions required 2–6 traversals (average >1), with traversal density and track length nearly constant across hamster and mouse lines but lower in human fibroblasts, yielding an RBE of ~3.8 at 10% survival and indicating that alpha‑sensitive lines are also gamma‑sensitive.

Abstract

Cell inactivation after exposure to collimated 3.5-MeV alpha particles in three hamster cell lines, V79, CHO-10B, and HS-23, one mouse cell line, C3H 10T1/2, and a human skin fibroblast cell line were studied. Several parameters were investigated for each cell line. Theoretical calculations were performed to find the distribution of energy deposited in the nuclear volume for each cell line. The mean number of alpha-particle traversals required to induce a lethal lesion varied between two for HS-23 cells and six for C3H 10T1/2 cells. The number of traversals per unit area and the total track length of alpha particles that inactivated a cell were found to be nearly constant for the hamster and mouse cell lines. These quantities were found to be lower for the human skin fibroblast cell line. The RBE values for all cell lines were found to be about 3.8 at 10% survival. Thus cell lines that are more sensitive to alpha radiation are also more sensitive to gamma radiation. The average number of alpha-particle traversals producing a single lethal lesion is greater than one. The passages of alpha particles through the cell nucleus that do not kill the cell may lead to carcinogenic effects.