Quantification of pulmonary regurgitation in patients with repaired Tetralogy of Fallot by 2D phase-contrast MRI: Differences between the standard method of velocity averaging and a pixel-wise analysis

Abstract

Objectives: To compare the values of pulmonary regurgitation in patients with repaired Tetralogy of Fallot quantifiedfrom two-dimensional phase-contrast data, by using a new pixel-wise analysis and the standard velocity-averagingmethod.Design: Quantitative in silico and in vivo analysis.Setting: Hospital So´tero del Rı´o. The magnetic resonance images were acquired using a Philips Achieva 1.5T scanner.Participants: Twenty-five patients with repaired Tetralogy of Fallot who underwent cardiovascular magnetic resonanceimaging requested by their referring physicians were included in this study.Main outcome measures: Using a computational fluid dynamics simulation, we validated our pixel-wise method,quantifying the error of our method in comparison with the standard method. The patients underwent a standard twodimensionalphase-contrast magnetic resonance imaging acquisition for quantifying pulmonary artery flow. Pulmonaryregurgitation fraction was estimated by using our pixel-wise and the standard method. The two-dimensional flowprofiles were inspected looking for simultaneous antegrade and retrograde flows in the same cardiac phase.Statistical analysis was performed with t-test for related samples, Bland–Altman plots, and Pearson correlationcoefficient.Results: Estimation of pulmonary regurgitation fraction using the pixel-wise analysis revealed higher values comparedwith the standard method (39 16% vs. 30 22%, p-value <0.01). Eight patients (32%) had a difference of more than10% between methods. Analysis of two-dimensional flow profiles in these patients revealed simultaneous antegrade andretrograde flows through the pulmonary artery during systole–early diastole.Conclusion: Quantification of pulmonary regurgitation fraction in patients with repaired Tetralogy of Fallot through apixel-wise analysis yields higher values of pulmonary regurgitation compared with the standard velocity-averagingmethod.