Fig. 1

Reference sequences for main pulmonary arterial (MPA) phase contrast imaging were two double-oblique orthogonal views along the main axis of the pulmonary trunk (a). The endocardial border of the MPA was manually outlined at all 20 reconstructed cardiac phases (b and c) permitting flow velocity profiles to be generated at rest and hyperemia (d and e respectively: flow velocity in ml/s on y axis and time in milliseconds on x axis). MeanPAvel was calculated as the average blood flow velocity across all cardiac phases. Ao = aorta, RV = right ventricle, RVOT = right ventricular outflow tract