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BED Calculator (Biological Effective Dose)DS-GPA Score (Diagnosis-Specific GPA)EQD2 Calculator (Equivalent Dose in 2Gy)GPA Score (Graded Prognostic Assessment)Iso-effective Dose Converter NSD Calculator (Ellis Formula)RPA Grading for Brain Metastases Radiation Necrosis MRI Index SRS Dose Selection (RTOG)TDF Factor (Time-Dose-Fractionation)

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Radiation Oncology

Iso-effective Dose Converter

Radiobiology Core: Iso-effect Converter

Reference (Initial) Plan

Total Dose (Gy)

Dose Per Fraction (Gy)

Target (New) Plan

New Dose Per Fx (Gy)

α/β Ratio (Gy)

Equivalence Engine

Determine the necessary dose adjustment when switching treatment techniques or schedules.

Guidelines & Evidence

Verified

Last Review: 2026

Iso-effective Concept

Mathematical Equivalence

An iso-effective dose calculation determines the total dose ($D_2$) required in a new fractionation schedule (with dose per fraction $d_2$) to achieve the same Biologically Effective Dose (BED) as an initial schedule ($D_1, d_1$). This is critical when changing treatment intent or technique mid-course.

The Iso-effect Formula

$$D_2 = D_1 imes rac{d_1 + alpha/eta}{d_2 + alpha/eta}$$ Where $D_1$ is the reference dose and $D_2$ is the target dose.

Last Comprehensive Review: 2026