RADIOBIOLOGY OF ALPHA-PARTICLES .3. CELL INACTIVATION BY ALPHA-PARTICLE TRAVERSALS OF THE CELL-NUCLEUS

Cell inactivation after exposure to collimated 3.5-MeV α 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 α-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 α 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 α radiation are also more sensitive to γ radiation. The average number of α-particle traversals producing a single lethal lesion is greater than one. The passages of α particles through the cell nucleus that do not kill the cell may lead to carcinogenic effects.