The Transit-Time method for measuring PWV. Anatomical (left) and velocity-encoding (right) images showing cross sections of the main pulmonary artery (up) and right pulmonary artery (down). The curves (right) show the velocity waves at MPA and RPA. The transit time (Δt) is measured between the curves feet. The curve foot is determined as the intersection between the baseline velocity (solid horizontal line) and slope of the up-steeping edge (dotted line). PWV is determined as the ratio of the distance between the two measurement sites (Δx) and the transit time (Δt).