Physics-constrained intraventricular vector flow mapping by color Doppler.

Area of Science:

• Cardiovascular Imaging
• Biomedical Engineering
• Fluid Dynamics

Background:

• Color Doppler echocardiography provides limited, one-component velocity data.
• Accurate assessment of intraventricular blood flow requires full velocity vector information.
• Existing methods for vector flow mapping have limitations in accuracy and clinical applicability.

Purpose of the Study:

• To improve the intraventricular vector flow mapping (iVFM) numerical scheme by incorporating physical fluid dynamics constraints.
• To validate the enhanced iVFM method using computational fluid dynamics (CFD) data and in vivo echocardiographic measurements.
• To assess the clinical potential of physics-constrained iVFM for evaluating cardiac function, particularly diastolic function.

Main Methods:

• Developed a physics-constrained iVFM algorithm by minimizing Doppler residuals subject to mass conservation and free-slip boundary conditions.
• Employed the Lagrange multiplier method and finite-difference discretization in a polar coordinate system to solve the optimization problem.
• Validated the method using patient-specific CFD data and in vivo color Doppler echocardiography.

Main Results:

• Physics-constrained iVFM demonstrated excellent agreement with CFD-derived velocity vectors (0.3%-12% relative error).
• Macroscopic flow measures (vorticity, stream function) showed high concordance between the enhanced iVFM and CFD.
• The algorithm successfully deciphered intraventricular flow patterns, including vortices during rapid filling, in in vivo data.

Conclusions:

• The physics-constrained iVFM algorithm significantly enhances the accuracy of cardiac blood flow vector reconstruction from echocardiography.
• This validated method is ready for clinical implementation and shows promise for improving the assessment of diastolic function.
• The approach offers a powerful tool for detailed hemodynamic analysis in clinical echocardiography.