Inactivation of Human Kidney Cells by High-Energy Monoenergetic Heavy-Ion Beams

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Abstract
Accelerated heavy particles are candidates for use in cancer therapy. The primary purpose of this investigation was to study the dose-effect relationships for asynchronous human kidney T-1 cells at various values of residual range for monoenergetic beams of carbon (400 MeV/amu), neon (425 MeV/amu) and argon (570 MeV/amu). The track segment method of exposure was used to minimize variations in the distribution of energy transfer events; secondary fragments produced by the particles in their passage through matter were, however, unavoidably included. Cell survival was measured after exposure to charged-particle beams under aerobic and hypoxic conditions over a range of mean LET.infin. [linear energy transfer] from 10-600 keV/.mu.m. Survival curves were characterized by an exponential and a nonlinear component. Using 3 current models for cellular inactivation, including the linear-quadratic model, it was found that the linear inactivation coefficient increased dramatically with increasing particle charge and decreasing particle velocity. The quadratic coefficient was dependent on LET. Dose and mean LET.infin. by themselves were not sufficient to characterize cellular responses. Although normal and tumor cells are known to have a range of biological properties, the results presented are basic to a fundamental understanding of the biological effects of charged particles. In addition, the data are relevant to future therapeutic uses of heavy ions.

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