ToolsCalculators
Radiation Biologically Effective Dose (BED)
Converts a fractionated radiation schedule to biologically effective dose and EQD2.
Radiation Biologically Effective Dose (BED)
Number of fractions
fractions
Dose per fraction
Gy
Alpha/beta ratio
Gy
Complete the fields above to see the result.
When to use
- Comparing radiotherapy schedules with different fraction sizes on a common biological scale.
Formula
BED = n x d x (1 + d / (alpha/beta)), where n is the number of fractions and d the dose per fraction. EQD2 = BED / (1 + 2/(alpha/beta)). Alpha/beta is about 10 Gy for most tumors and early-reacting tissue, 3 Gy for late-reacting tissue.
Pearls and pitfalls
- The linear-quadratic model becomes less reliable at very large fraction sizes used in stereotactic regimens.