Indexing and normalization
Indexing converts raw measurements into body-size-normalized, length-normalized, or pressure-normalized values. These derived rows are useful, but they introduce external denominators and missingness.
- Modality
- All modalities
- Pipeline step
- Derived feature extraction and normalization
- Outputs
- BSA-indexed volumes/mass/diameters, cardiac index, pressure-normalized distensibility, length-normalized torsion
- Maturity
- Source-audited method page
Common normalizations
| Normalization | Current use | Dependency |
|---|---|---|
| BSA indexing | ventricular volumes, atrial volumes/dimensions, myocardial mass, LVOT diameters | query_BSA / available BSA table |
| Cardiac index | cardiac output divided by BSA | heart rate and BSA |
| Length normalization | torsion and recoil rows | ventricular length or method-specific length |
| Pressure normalization | aortic distensibility | central pulse pressure from configured pressure source |
| RR-indexed timing | tagged time-to-peak indices | usable ECG rest data and RR interval |
Interpretation rules
Indexed values should usually be displayed beside raw values rather than replacing them. Absolute size, body-size-adjusted size, and pressure-normalized stiffness answer different questions.
Missing denominator rule
If the denominator or external table is missing, the derived row should be unavailable or conditional. Do not interpret a missing indexed row as a normal raw measurement.
Current caveats
BSA, pressure, and ECG dependencies are not cosmetic metadata. They can change which rows are emitted for a subject. Aortic distensibility also filters central pulse pressure below the current validity threshold, and tagged timing indices are skipped when ECG rest data are unavailable.
Source audit
- BSA-indexed row behavior was checked against current ventricular, atrial, LVOT, and native feature documentation.
- Pressure-normalized distensibility behavior was checked against
eval_aortic_dist.py. - RR-indexed tagged timing behavior was checked against
eval_strain_tagged.py. - Textbook context boundary: broad clinical textbook context is not surfaced here because this page documents normalization mechanics.