Impairment of the Proliferative Capacity of Human Cells in Culture by α-particles with Differing Linear-energy Transfer

Summary

Inhibition of clone-formation was measured after irradiation of cultured human cells by α-particles with different ionization densities. The results show that the RBE of these particles, as a function of the LET, increases between 25 and 100 kev/µ of unit density tissue, passes through a maximum of about 8 at 110 kev/µ and subsequently decreases.

The effectiveness per particle, calculated as the effective cross-section for impairment of the proliferative capacity, increases between 25 and 100 kev/µ of unit density tissue and approaches a maximum of 35 µ² at higher LET values. These results are discussed on the basis of a hypothesis, whereby it is assumed that a given number of n or more ionizations must be produced within a length of the particle track t, in order to cause, through a cooperative action, damage to the reproductive capacity of the cells.