Tap the selected calculated dose to lock it as an approximate target. NOT A MEDICAL DEVICE!
Simple radiobiology calculator
Enter a schedule to calculate BED and EQD₂. Direct number entry, with no target locks or time/recovery adjustments.
Educational calculation only. Not a medical device or a treatment recommendation.
Formulas & colour guide
Physical dose = n × d. BED = n × d × (1 + d / (α/β)). EQD₂ = n × d × (d + α/β) / (2 + α/β). Results use the unrounded input values and are displayed to one decimal place.
The top result uses your selected α/β; the rows below use 1.5, 2, 3 and 10. Reference colours are yellow, blue, green and red respectively. EQD₂ is dark; BED is softer grey.
Inset fields run from green (lower) to red (higher), scaled separately within the EQD₂ and BED columns. Equal values receive the same middle colour. Colours are not safety limits.
This tab has independent inputs. “Copy from tab 1” copies the current fractions, dose/fx and α/β, without changing or copying its lock. Fractions: 1–100; dose/fx: 0.01–20 Gy; α/β: 0.1–30 Gy.
Compare & add regimens
Compare schedules below. Include only the courses you want to add together. Regimen results use α/β A; the included total is calculated separately at both α/β A and B.
Remaining effect: 1.0 = 100% retained; 0.1 = 10% retained (90% discounted). This manually chosen factor multiplies BED and EQD₂ only. Physical dose is unchanged. Not a validated recovery model or a medical device.
α/β A
α/β B
Calculation & recovery assumptions
For each regimen: physical dose = n × d; BED = n × d × (1 + d / (α/β)); EQD₂ = BED / (1 + 2 / (α/β)). Factor-adjusted values = remaining-effect factor × the corresponding unadjusted value. Totals add only the included rows, using full precision before display rounding.
A factor of 0.3 retains 30% of that regimen’s biological dose; it does not mean 30% recovery. All factors default to 1.0. No time-based, tissue-specific, or spatial dose-overlap model is implemented.
Recovery is uncertain and tissue-dependent; cumulative clinical evaluation requires more than scalar dose addition. See RCR: Principles of reirradiation (2024). This page is exploratory and must not determine reirradiation safety.
Comparison values are independent of the calculator’s target lock. “From calculator” copies fractions and dose/fx only; each regimen row uses α/β A. The same included regimens are summed separately at α/β A and B, using the same remaining-effect factors in both. Each sum assumes consistent tissue/endpoint dose inputs across its included courses; changing α/β alone does not substitute actual organ-specific dose information. Data are kept only while this page is open and reset on reload.
Treatment compensation
Explore additional fractions after a treatment interruption. Adapted from RTCC v0.8 with corrected time-loss calculations and independent delivered doses and calendar durations.
Exploratory model, not a prescription. The starting values reproduce the original RTCC example, not a recommended regimen. Time-loss parameters and α/β assumptions require independent clinical review. Not a medical device.
Originally planned
Already delivered
Additional treatment to explore
Final elapsed time = elapsed days + additional days. Include any future waiting period in the additional days; fractions and days are independent.
Biological & time-loss assumptions
Tumour time loss = k × max(elapsed time − onset, 0). The same expression is used when solving and evaluating the result. No late-effect recovery is modelled here.
Interpolated compensation dose
Late-effect BED
Tumour BED
*Tumour BED includes the time-loss term. These are modelled dose ratios, not toxicity or tumour-control probabilities. Dose/fx is displayed to 3 decimals; totals use the unrounded solution.
Compensation map
Rows explore 1–10 additional fractions; columns explore aggressivity 0–10. Click a cell to apply its fractions, days and aggressivity. Colours show relative numerical size, not treatment safety. Grey cells have no usable solution.
Equations, corrections & limitations
BED(n,d,a) = n × d × (1 + d/a). Let L(T) = k × max(T − onset, 0). Planned late BED = BED(nₚ,dₚ,aₗ); planned tumour BED = BED(nₚ,dₚ,aₜ) − L(Tₚ).
The extra late-effect BED budget is planned late BED − BED(nₐ,dₐ,aₗ). The extra tumour BED budget is planned tumour BED + L(Tₐ + T꜀) − BED(nₐ,dₐ,aₜ). Each endpoint solves n꜀ × d × (1 + d/a) = its budget for non-negative d. The interpolated dose is dₗ + (aggressivity/10) × (dₜ − dₗ).
Corrections to the supplied RTCC v0.8: no negative pre-onset time loss, delivered dose is used for the delivered course, compensation duration is independent of fractions, numerical state is never parsed from formatted output, and every field updates immediately. The map uses independent calculations and does not silently alter the current scenario.
A negative remaining BED budget has no non-negative endpoint solution. A non-positive planned time-adjusted tumour BED cannot support a meaningful percentage ratio. These cases are reported, not converted into a negative dose or NaN. Zero additional dose is shown only as a mathematical endpoint, not a treatment instruction.
PDI reproduces the original custom score using fractional ratios rₜ and rₗ: 100 × [(rₜ ≤ 1 ? (1 − rₜ)² : −(rₜ − 1)²/10) + (rₗ ≥ 1 ? (rₗ − 1)² : −(1 − rₗ)²/10)]. It is not a validated probability, constraint or optimisation recommendation.
Elapsed time uses the durations exactly as entered, without a calendar, weekend scheduler or automatic inclusive-day correction. The calculation has no spatial dose model, clinical dose constraints, tissue-specific parameter recommendations or intraday repair model. Do not use it to determine a safe compensation schedule. All three tabs keep independent settings; this tab does not apply the comparison tab’s remaining-effect factors.