Brief summary of radiobiological principles in fractionated radiotherapy

Summary of LQ Formula

To calculate BED or ERD without a time factor, see equation (4). To calculate BED or ERD with a time factor, see equation (8). BED or ERD are written as Gy₃ or Gy₁₀ for late- and early-responding tissues, respectively. Midrange values, for a first calculation, would be α/β=3 Gy for late; α/β=10 Gy for earlyresponding tissues and most tumors; α=0.3−0.35 Gy⁻¹; T_eff=2 to 30 days (median 5 days); T_k=14 to 28 days (subtracted from overall time). These formulae are used for the intercomparisons of schedules in the final article in this issue.