Fig. 2.

Calculation of pulmonary-to-systemic arterial flow ratio (Qp/Qs) using velocity-encoded phase-contrast cine MRI in a 24-year-old female with a secundum atrial septal defect.

A. An imaging plane perpendicular to the long axes of the aorta and main pulmonary artery is prescribed.

B, C. ROIs were drawn on the pulmonary artery and aorta on the cine images (magnitude images on the left plots of B, C). Curves on the right plots show flow volume versus ECG-trigger delay time. Flow volume of the pulmonary artery and aorta was 8,498 ml/min and 5,833 ml/min, respectively, with a Qp/Qs of 1.5. In this patient, the Qp/Qs determined by radioisotope study was 1.7.