Radiomics-Derived Ischemia Burden Score (R-IBS) Calculator

Radiomics-Derived Ischemia Burden Score (R-IBS): Explanation and Clinical Context This calculator estimates global ischemic burden by blending per-vessel radiomics probabilities of functional ischemia with optional CT-derived fractional flow reserve (CT-FFR). Radiomics “Rad-signature” values represent the probability that a given coronary vessel supplies an ischemic territory; these were derived from pericoronary tissue features on coronary CT angiography (CCTA) using machine learning, validated against CT-FFR ≤0.80. Each vessel probability is weighted by myocardial territory according to coronary dominance: LAD (~50%), LCx (~20–35%), RCA (~15–30%).

The resulting weighted sum represents total ischemic myocardium as a percentage of the left ventricle. Clinical interpretation: Ischemic burden <5% indicates low risk, 5–10% borderline/intermediate, and >10% moderate-to-severe burden. These thresholds are extrapolated from nuclear perfusion studies and should be interpreted within the clinical context.