Comparison of calculated dosimetric values from simple homogenous spheres and Monte Carlo (MC) results. (a) The model-calculated SF compared to the individual cell Monte Carlo surviving fraction. The dotted line represents equivalence. (b) A similar comparison for the EUD, where the round circles show the average absorbed dose, that is, the simple sphere values before statistical adjustment. (c) and (d) The same EUD comparisons for different α and β values: for (c), α = 0.0451 Gy−1 and β = 0.0051 Gy−2; for (d), α = 4.51 Gy−1 and β = 5.1 Gy−2.