How this calculator works
The hemispherical flow-convergence method estimates instantaneous flow toward a regurgitant orifice. Divide that flow by the simultaneous peak regurgitant jet velocity for EROA, then multiply by the regurgitant VTI for volume. The simple model assumes a hemispherical shell and a representative orifice through systole; eccentric or multiple jets and changing orifice shape can invalidate it. The result is an estimate for information only and is not medical advice.
Formula
Flow(mL/s) = 2πr²Va; EROA(cm²) = Flow/Vmax; RVol(mL) = EROA × VTI. r and VTI are in cm, velocities in cm/s.
Worked example
With r 0.8 cm, Va 40 cm/s and Vmax 500 cm/s, flow is 160.8495 mL/s and EROA 0.3217 cm². VTI 100 cm gives 32.1699 mL.
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Frequently asked questions
Is PISA radius a diameter?
No. Enter the radius from the orifice to the aliasing contour.
Can I grade regurgitation from this alone?
No. Guidelines require integrated assessment with other Doppler and structural findings.
What if the convergence region is constrained?
The full hemispherical assumption can fail. The PISA page includes an explicit angle factor.