Fig. 1

a Frontal radiograph of a patient with sinus venosus atrial septal defect demonstrates a dilated pulmonary artery, pulmonary oedema, left pleural effusion and cardiomegaly. The right lower lobe pulmonary artery measures 26 mm. b Contrast-enhanced axial CT image demonstrates an enlarged main pulmonary artery in the same patient. The pulmonary artery to aorta ratio is 1.9. c Axial steady state free precession images in the same patient demonstrate enlarged pulmonary artery (arrow). d Pulmonary artery distensibility (1.8 %) can be calculated using cine MR, by measuring the diastolic minimal (10.9 cm²) and systolic maximal (11.1 cm²) cross-sectional area obtained perpendicular to direction of blood flow. e Average velocity obtained with phase contrast MR in the main pulmonary artery is 11.6 cm/s