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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.

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 Bed Calculation, Eqd2 Dose Calculator or the Tdf Factor Calculator to formulate a comprehensive care plan.

Last Comprehensive Review: 2026

Related Radiation Oncology Tools

EQD2 Calculator

Iso-effective Dose Converter

Radiation Necrosis MRI Index

RPA Grading for Brain Metastases

SRS Dose Selection

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