Radiobiology of α Particles. IV. Cell Inactivation by α Particles of Energies 0.4-3.5 MeV

In this report the effectiveness of low-energy α particles in the range 0.4 to 3.5 MeV for cell killing is investigated. Four cell lines of different nuclear dimensions (AG1522, C3H 10T1/2, CHO-10B, and HS-23) are studied. Monte Carlo simulations are carried out to interpret the experimental results. They are presented as a function of dose to the nucleus, the total track length of α particles in the nucleus, and other parameters. It is found that the effectiveness of α particles for cell killing decreases with decreasing α-particle energy. The maximum RBE value is found to extend to LET values as high as 180 keV/μm. Although the LET might be the same, the effectiveness of α particles for cell killing is higher in the ascending part of the Bragg curve compared to descending part of the Bragg curve. The terminal tracks of α particles are observed to be less effective for cell killing.