The ultrasonic colored Doppler image is convenient to observe blood flow in the human heart. This image displays the velocity component in the direction of the ultrasonic beam. Therefore, it is difficult to point out the existence of vorticity in the flow. An extended stream function method is being developed in order to show streamlines over the colored Doppler image. The Doppler velocity in the image is the local velocity component governed under rules of fluid dynamics. Considering this, two-dimensional velocity components were estimated in the observing plane appearing as the colored Doppler image. Clinical data show that vortexes in blood flow play very important roles in the behavior of the mitral valve in the heart.