1,329 calculators and references across 60 specialties, with formula confidence shown up front.
4D Flow MRI Helicity Index (HI): Explanation and Clinical Context Helicity quantifies the local alignment between velocity and vorticity in a flow field. In cardiovascular 4D Flow MRI, the helicity density is the dot product of the velocity vector and vorticity (the curl of velocity), and its normalized form—Local Normalized Helicity (LNH)—is defined as LNH = (v · ω) / (|v||ω|), ranging from −1 (left-handed) to +1 (r
Aortic Compliance Index (ACI): Explanation and Clinical Context The Aortic Compliance Index (ACI) represents the ability of the aorta to expand and contract with each cardiac cycle in response to changes in blood pressure. It reflects the elastic properties of the aortic wall and serves as a surrogate marker of arterial stiffness. The formula used is: ACI = Stroke Volume / Pulse Pressure where Stroke Volume (SV) is t
CAC Percentile (MESA Reference): Explanation and Clinical Context The Coronary Artery Calcium (CAC) Percentile, based on the Multi-Ethnic Study of Atherosclerosis (MESA) reference equations, provides an age-, sex-, and race-specific comparison of an individual’s coronary calcium burden against a large, population-based cohort. It contextualizes the raw Agatston score by expressing it as a percentile of expected CAC f
Optional — Plaque and Calcium Context (for display only) Agatston Calcium Score (CACS) High-Risk Plaque (HRP) features count (0–4) Custom Radiomic Signature (from a publication) — Logistic Model Use when you have coefficients from an original paper (intercept and feature weights). Calculator will output linear predictor and probability. Intercept (β0) Feature 1 Name Value (x1) Coefficient (β1) Feature 2 Name Value (x
Inputs for Systolic Dyssynchrony Index (SDI; time-to-peak based) CMR Feature Tracking Dyssynchrony Index: Explanation and Clinical Context Cardiovascular magnetic resonance feature tracking (CMR-FT) enables derivation of strain-time curves from standard SSFP cine images without additional tagging sequences. Mechanical dyssynchrony can be quantified in two complementary ways. First, a systolic dyssynchrony index (SDI)
: Explanation and Clinical Context Extracellular Volume Fraction (ECV%) quantifies the proportion of myocardial tissue that is extracellular space, as derived from pre- and post-contrast T1 mapping in cardiac magnetic resonance imaging (CMR). It reflects interstitial expansion caused by fibrosis, edema, or infiltration. The ECV is calculated using native and post-contrast myocardial and blood T1 values, adjusted for
LV Diastolic Stress Test Index: Explanation and Clinical Context The Left Ventricular (LV) Diastolic Stress Test Index, primarily expressed as the ratio of early mitral inflow velocity (E) to early diastolic annular velocity (e′) during peak exercise, is a validated echocardiographic parameter to assess left ventricular filling pressures under stress conditions. A normal response (E/e′ < 10) suggests adequate relaxat
Left Ventricular Sphericity Index (LVSI): Explanation and Clinical Context The Left Ventricular Sphericity Index (LVSI) is a ratio of the left ventricular short-axis diameter to the long-axis length measured at end-diastole. It quantifies the geometric remodeling of the left ventricle from a normal ellipsoid shape toward a more spherical form. A higher LVSI indicates a more spherical ventricle, which is often associa
MRI-LGE Extent (% LV Mass Fibrosis): Comprehensive Explanation and Clinical Context This calculator estimates the proportion of myocardial fibrosis (late gadolinium enhancement, LGE) relative to total left ventricular (LV) mass using cardiac MRI data: %LGE = (LGE mass / LV mass) × 100. When input volumes are provided, they are converted to grams assuming a myocardial density of 1.05 g/mL. LGE reflects focal myocardia
Myocardial Flow Reserve (MFR): Explanation and Clinical Context Myocardial Flow Reserve (MFR) is a quantitative index derived from positron emission tomography (PET) myocardial perfusion imaging, calculated as the ratio of hyperemic (stress) myocardial blood flow (MBF) to resting MBF. An MFR value below 2.0 is considered abnormal and reflects impaired coronary vasodilator capacity, which may result from epicardial co
Calculate Global Longitudinal Strain (GLS), Global Circumferential Strain (GCS), and Global Radial Strain (GRS) Myocardial Strain (GLS, GCS, GRS): Comprehensive Explanation and Clinical Context Myocardial strain quantifies myocardial deformation as a percentage change from the end-diastolic state. Global Longitudinal Strain (GLS) reflects the shortening of subendocardial longitudinal fibers and is reported as a negat
Myocardial Work Efficiency Index (MWEI): Explanation and Clinical Context The Myocardial Work Efficiency Index (MWEI) is a novel, non-invasive echocardiographic parameter derived from left ventricular (LV) pressure–strain loops. It integrates LV deformation (strain) and afterload to evaluate the energy efficiency of myocardial contraction. The index is calculated as the ratio between Global Constructive Work (GCW)—th
Native T1 Mapping Index (T1 Time): Comprehensive Explanation and Clinical Context Native myocardial T1 reflects the longitudinal relaxation of protons in tissue and rises with increased free water or extracellular matrix expansion (edema, diffuse fibrosis, amyloidosis) and falls with intracellular storage (Anderson–Fabry, iron overload). Absolute T1 values depend on magnetic field strength (1.5T vs 3T) and mapping se
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
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 tis
Right Ventricular Global Longitudinal Strain (RV-GLS): Explanation and Clinical Context RV-GLS quantifies right ventricular systolic deformation along the longitudinal axis from an RV-focused apical four-chamber view using 2D speckle-tracking. Two reporting conventions exist: a 6-segment global value that includes free wall and septum (RV-GLS), and a 3-segment free-wall-only value (RVFWLS). Because septal motion is i
Inputs (all numeric, use dot for decimals) T2 Mapping Edema Index: Explanation and Clinical Context T2 mapping quantifies myocardial transverse relaxation time (T2) in milliseconds on a pixel-wise basis. Elevated myocardial T2 reflects increased free water and serves as a quantitative index of myocardial edema. About the parameters: • T2 (ms): quantitative value representing water content in myocardium. • Z-score: de
Vascular Remodeling Radiomic Risk Model: Explanation and Clinical Context This calculator operationalizes a published perivascular fat radiomic profile (FRP) derived from coronary CT angiography to reflect adverse perivascular adipose tissue remodeling (fibrosis and microvascular changes) that accompanies chronic coronary inflammation. The original model was trained via machine learning (random forest) using hundreds
Wall Shear Stress Gradient Index (WSSG): Explanation and Clinical Context Wall Shear Stress Gradient (WSSG) represents the spatial rate of change in wall shear stress (WSS) along the vessel surface and is a critical biomechanical determinant of endothelial behavior. It quantifies how rapidly the tangential force exerted by flowing blood varies over a given vascular segment. In normal arterial physiology, WSS remains