Examinando por Autor "Mella, Hernan"

Mostrando 1 - 2 de 2
  • Miniatura
    Ítem
    Non-invasive local pulse wave velocity using 4D-flow MRI
    (Elsevier, 2021) Mura, Joaquín; Sotelo, Julio; Mella, Hernan; Wong, James; Hussain, Tarique; Ruijsink, Bram; Uribe, Sergio
    Pulse Wave Velocity (PWV) corresponds to the velocity at which pressure waves, generated by the systolic contraction in the heart, propagate along the arterial tree. Due to the complex interplay between blood flow and the artery wall, PWV is related to inherent mechanical properties and arterial morphology. PWV has been widely accepted as a biomarker and early predictor to evaluate global arterial distensibility. Still, several local abnormalities often remain hidden or difficult to detect using non-invasive techniques. Here, we introduce a novel method to efficiently construct a local estimate of PWV along the aorta using 4D-Flow MRI data. A geodesic distance map was used to track advancing pulses for efficient flow calculations, based on the observation that the propagation of velocity wavefronts strongly depends on the arterial morphology. This procedure allows us a robust evaluation of the local transit time due to the pulse wave at each position in the aorta. Moreover, the estimation of the local PWV map did not require centerlines, and the final result is projected back to 3D using the same geodesic map. We evaluated PWV values in healthy young and adult volunteers and patients with univentricular physiology after a Fontan procedure. Our method is fast, semi-automatic, and depicts differences between young versus adult volunteers and young volunteers versus Fontan patients, showing consistent results compared to global methods. Remarkably, the technique could detect local differences of PWV on the aortic arch for all subjects, being consistent with previous findings of reduced PWV in the aortic arch.
  • Miniatura
    Ítem
    Three-dimensional quantification of circulation using finite-element methods in four-dimensional flow MR data of the thoracic aorta
    (Wiley, 2022) Sotelo, Julio; Bissell, Malenka M.; Jiang, Yaxin; Mella, Hernan; Mura, Joaquín; Uribe, Sergio
    Purpose. Three-dimensional (3D) quantification of circulation using a Finite Elements methodology. Methods. We validate our 3D method using an in-silico arch model, for different mesh resolutions, image resolution and noise levels, and we compared this with a currently used 2D method. Finally, we evaluated the application of our methodology in 4D Flow MRI data of ascending aorta of six healthy volunteers, and six bicuspid aortic valve (BAV) patients, three with right and three with left handed flow, at peak systole. The in-vivo data was compared using a Mann-Whitney U-test between volunteers and patients (right and left handed flow). Results.The robustness of our method throughout different image resolutions and noise levels showed subestimation of circulation less than 45 cm2/s in comparison with the 55cm2/s generated by the current 2D method. The circulation (mean ± SD) of the healthy volunteer group was 13.83 ± 28.78 cm2/s, in BAV patients with right-handed flow 724.37 ± 317.53 cm2/s, and BAV patients with left-handed flow −480.99 ± 387.29 cm2/s. There were significant differences between healthy volunteers and BAV patients groups (P-value < .01), and also between BAV patients with a right-handed or left-handed helical flow and healthy volunteers (P-value < .01). Conclusion. We propose a novel 3D formulation to estimate the circulation in the thoracic aorta, which can be used to assess the differences between normal and diseased hemodynamic from 4D-Flow MRI data. This method also can correctly differentiate between the visually seen right- and left-handed helical flow, which suggests that this approach may have high clinical sensitivity, but requires confirmation in longitudinal studies with a large cohort.