Radiobiology Core: BED Calculation
Fractionation Parameters
Ready for Calculation
Enter dose parameters to determine the biological potency of the fractionation schedule.
Guidelines & Evidence
Verified
Last Review: 2026
Radiobiology Background
The Linear-Quadratic (LQ) Model
The BED is based on the Linear-Quadratic model of cell kill, which posits that cell death results from both single-hit (alpha) and multi-hit (beta) lethal events. The BED provides a common language to compare the biological effect of radiation delivered with different dose per fraction and total dose. It is essential for planning dose escalations, hypo-fractionation (e.g., SBRT), or managing treatment interruptions.
Alpha/Beta (α/β) Ratios — Critical Values
| Tissue Type | Typical α/β | Characteristics | Examples |
|---|---|---|---|
| Early Responding | 10 Gy | Rapidly dividing tissues; linear response to dose. | Most tumors, skin, mucosa, gut. |
| Late Responding | 3 Gy | Slowly dividing tissues; highly sensitive to dose per fraction. | Spinal cord, brain, lung, kidney. |
| Prostate Cancer | 1.5 Gy | Unusually low α/β; behaves like late-responding tissue. | Primary prostate adenocarcinoma. |
| Breast Cancer | 3.5 Gy | Moderate α/β; supports moderate hypo-fractionation. | Primary breast adenocarcinoma. |
| Melanoma / RCC | 3 – 5 Gy | Relatively radioresistant tumors; respond well to large fractions. | SBRT targets. |
The BED Formula
$$BED = D imes left(1 + rac{d}{alpha/eta}
ight)$$ Where: D = Total Dose (Gy), d = Dose per Fraction (Gy), α/β = Tissue-specific ratio.
Related Scores in Practice
In clinical practice, this assessment is frequently evaluated alongside other validated measures. Depending on the patient's presentation and specific diagnostic requirements, you may also need to utilize the Eqd2 Dose Calculator, Iso-effective Dose Converter or the Tdf Factor Calculator to formulate a comprehensive care plan.
Last Comprehensive Review: 2026