bed calculator eqd2

What is BED and EQD2?

BED (Biologically Effective Dose) and EQD2 (Equivalent Dose in 2 Gy fractions) are radiobiology tools used to compare different fractionation schedules in radiation oncology. They are based on the linear-quadratic (LQ) model and help express how changes in dose per fraction may alter biological effect.

In plain terms: two regimens with the same physical total dose can have different biological impact if fraction size differs. BED and EQD2 provide a common language for that comparison.

How to use this BED calculator EQD2 tool

• Enter any two values among: total dose (D), dose per fraction (d), and number of fractions (n).
• Set an appropriate α/β value for the target tissue or organ at risk.
• Click Calculate BED & EQD2.
• The calculator computes missing plan values and displays BED and EQD2.

Example: if you enter D = 60 Gy and n = 30, the calculator infers d = 2 Gy/fraction automatically.

Quick reference formulas

1) BED formula

BED = nd[1 + d/(α/β)] = D[1 + d/(α/β)]

2) EQD2 formula

EQD2 = BED / [1 + 2/(α/β)]

where:

• D = total dose in Gy
• d = dose per fraction in Gy
• n = number of fractions
• α/β = tissue-specific parameter in Gy

Common clinical context for α/β

Different tissues respond differently to fraction size. In general educational use, people often discuss:

• ~10 Gy for many rapidly proliferating tumors (context-dependent)
• ~3 Gy for many late-responding normal tissues
• Lower values (e.g., around 1.5) are often discussed for specific disease sites such as prostate, depending on source

Always use institutional standards, protocol definitions, and clinician judgment for real treatment planning.

Worked examples

Conventional fractionation example

Suppose D = 60 Gy in 30 fractions, so d = 2 Gy. With α/β = 10 Gy:

• BED = 60 × (1 + 2/10) = 72 Gy
• EQD2 = 72 / (1 + 2/10) = 60 Gy

Hypofractionated example

Suppose D = 30 Gy in 5 fractions, so d = 6 Gy. With α/β = 3 Gy:

• BED = 30 × (1 + 6/3) = 90 Gy
• EQD2 = 90 / (1 + 2/3) = 54 Gy

Important limitations

• The LQ model is a simplification and may be less reliable in some high-dose-per-fraction settings.
• Time factors (overall treatment time, repopulation, treatment gaps) are not included in this basic calculator.
• Clinical outcomes depend on many variables beyond BED/EQD2 (geometry, heterogeneity, systemic therapy, patient factors).

This calculator is intended for educational and research support only. It is not a substitute for a certified treatment planning system or professional medical decision-making.

FAQ

Can I compare two plans directly?

Yes. Run each plan separately using the same α/β assumption and compare BED or EQD2 outputs.

What if all three D, d, and n values are entered?

If values are inconsistent (for example, D does not match n×d), the calculator warns you and still computes using derived relationships.

Which metric should I report?

In many publications and protocol discussions, EQD2 is convenient for cross-schedule comparison, while BED may be preferred for mechanistic interpretation.