Oncologic Imaging
Live dataTumour Volume (Ellipsoid)
Estimates tumour volume from three orthogonal diameters using the ellipsoid approximation.
The ellipsoid approximation models a lesion as a regular ellipsoid, giving a quick volume estimate from three orthogonal diameters without dedicated segmentation software. The constant 0.52 is π/6.
📐 Formula
Volume (mL) = 0.52 × A × B × C (π/6 × A × B × C)
🎯 When to Use
- Estimating volume of a mass, node or cyst from simple caliper measurements.
- Tracking interval growth and estimating tumour doubling time.
- When volumetric segmentation is unavailable or impractical.
⚙️ How It Works
- Measure three mutually perpendicular diameters A, B and C in centimetres.
- Multiply the three diameters and scale by π/6 ≈ 0.5236.
- Result is the ellipsoid volume in millilitres (cm³).
- For growth kinetics, serial volumes allow calculation of specific growth rate and doubling time.
📊 Interpreting the Result
- Volume doubling corresponds to a ~26% increase in a single diameter, so small linear changes reflect large volume changes.
- Short volume-doubling times (weeks) suggest aggressive disease; long times (>400 days) favour benign or indolent processes.
- Ellipsoid estimates track well with segmented volumes for reasonably regular masses.
⚠️ Limitations & Pitfalls
- Overestimates volume for irregular, spiculated or lobulated lesions.
- Sensitive to measurement error, amplified because errors multiply across three dimensions.
- Assumes the lesion is solid; cystic or necrotic components are not distinguished.
📚 References
- Feldman JP, Goldwasser R, Mark S, et al. A mathematical model for tumor volume evaluation using two-dimensions. J Appl Quant Methods. 2009;4(4):455-462.
- Schwartz M. A biomathematical approach to clinical tumor growth. Cancer. 1961;14:1272-1294.
⚕️ For clinical decision support only. Always verify calculations and apply clinical judgment.