For spatial resolutions of 1.5 and 2.5 mm, peak total turbulent kinetic energy downstream of a 75% aortic stenosis is overestimated by 15% and 24%, respectively, compared to ground truth.
Synthetic 4D flow MRI data generation reveals that typical clinical spatial resolutions and time averaging lead to significant overestimation of peak turbulent kinetic energy downstream of aortic stenoses.
We propose to synthesize patient-specific 4D flow MRI datasets of turbulent flow paired with ground truth flow data to support training of inference methods. Turbulent blood flow is computed based on the Navier-Stokes equations with moving domains using realistic boundary conditions for aortic shapes, wall displacements and inlet velocities obtained from patient data. From the simulated flow, synthetic multipoint 4D flow MRI data is generated with user-defined spatiotemporal resolutions and reconstructed with a Bayesian approach to compute time-varying velocity and turbulence maps. For MRI data synthesis, a fixed hypothetical scan time budget is assumed and accordingly, changes to spatial resolution and time averaging result in corresponding scaling of signal-to-noise ratios (SNR). In this work, we focused on aortic stenotic flow and quantification of turbulent kinetic energy (TKE). Our results show that for spatial resolutions of 1.5 and 2.5 mm and time averaging of 5 ms as encountered in 4D flow MRI in practice, peak total turbulent kinetic energy downstream of a 50, 75 and 90% stenosis is overestimated by as much as 23, 15 and 14% (1.5 mm) and 38, 24 and 23% (2.5 mm), demonstrating the importance of paired ground truth and 4D flow MRI data for assessing accuracy and precision of turbulent flow inference using 4D flow MRI exams.
Dirix et al. (Mon,) conducted a other in Aortic stenosis. Synthetic 4D flow MRI vs. Computational Fluid Dynamics (CFD) ground truth was evaluated on Peak total turbulent kinetic energy (TKE) overestimation. For spatial resolutions of 1.5 and 2.5 mm, peak total turbulent kinetic energy downstream of a 75% aortic stenosis is overestimated by 15% and 24%, respectively, compared to ground truth.