Native T1 Mapping Index (T1 Time) Calculator

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 sequence (MOLLI, ShMOLLI, SASHA). Purpose of this tool: This calculator standardizes a patient's native T1 value relative to published reference means (sequence- and field-specific) as a z-score.

Values beyond ±2 suggest abnormal tissue composition and warrant correlation with clinical findings and CMR pattern recognition. Reference-based thresholds: For 3T, a global native T1 ≥1341 ms identifies cardiac amyloidosis vs HCM/HHD with sensitivity 100% and specificity 97% (Lavall et al., 2023). At 1.5T, <1036 ms rules out (NPV 98%) and >1164 ms rules in (PPV 98%) cardiac amyloidosis (JACC 2019).

Clinical interpretation summary: High T1 (z>2): edema, diffuse fibrosis, amyloidosis. Low T1 (z<-2): Anderson–Fabry disease or iron deposition. Sequence type, field strength, and region-of-interest placement strongly influence absolute values; local reference calibration is advised for precise thresholding.