Doppler color flow of the main pulmonary artery

A short-axis cut through the cardiac base demonstrates the long-axis projection of the main pulmonary artery (MPA). The Doppler flow information is color encoded so that flow in all parts of the artery can be displayed. In this systolic frame, flow should be entirely away from the transducer, or blue in color; however, much of the color shown is red hued, indicating that flow exceeds 0.48 m/s. This color change indicates aliasing, not reversed flow.