Spatial distribution of effects of negative poins on cultured human cells.

Cultured human kidney T-1 cells were irradiated in flasks or on coverslips at different depths in a water phantom using the Los Alamos Meson Physics Facility Biomedical negative pion beam. Postirradiation colony formation and cell multiplication were assayed. Maximum cell inactivation occurred in the vicinity of maximum pion dose. Comparison of dose-survival curves with those found following x irradiation indicated RBE = 1.4 plus or minus 0.3 for colony formation and approximately 1.5 for growth delay. Delivery of 400 pion rads in four fractions resulted in higher survival than did delivery of 400 rads in a single fraction.