Pericoronary Fat Attenuation Index (FAI) Calculator

LAD FAI (HU) (optional) Tube voltage (kVp) 120 100 Other/Unknown High-Risk Plaque (HRP) present on CCTA? No / Not reported Yes (≥1 HRP feature) Coronary Artery Calcium Score (Agatston) (optional) Pericoronary Fat Attenuation Index (FAI): Comprehensive Explanation and Clinical Context Pericoronary (or perivascular) Fat Attenuation Index (FAI) is a CT-derived biomarker representing vascular inflammation by quantifying the mean attenuation of adipose tissue voxels (–190 to –30 HU) around the proximal coronary arteries within a radial distance equal to the vessel diameter. A higher (less negative) FAI value reflects lipid-poor, water-rich fat consistent with active vascular inflammation.

Validated Threshold and Prognostic Value The CRISP-CT study defined an elevated FAI as ≥ –70.1 HU (proximal RCA). Elevated FAI independently predicted cardiac mortality and myocardial infarction beyond risk factors, calcium score, and plaque features. Patients with elevated FAI had up to ninefold higher risk, while lower FAI values showed strong negative predictive value.

Acquisition and Technical Considerations Measurements are performed using CCTA datasets with semi-automated software. Only voxels –190 to –30 HU are included, measured 10–50 mm from the RCA ostium (excluding first 10 mm). The validated threshold assumes 120 kVp acquisition; results from other kVp settings should be interpreted with caution or using device-calibrated “FAI-Score”.

Clinical Interpretation Summary RCA FAI ≥ –70.1 HU → elevated inflammation and higher cardiovascular risk. RCA FAI < –70.1 HU → low inflammatory signal, lower event risk. Integrate with HRP and calcium score for overall assessment.