Since the sample data set available online was not originally intended for a Doppler study, no Doppler angle measurements are recorded on the image as would be the case in a clinical Doppler study. Hence, the true Doppler angle (ground truth) was independently measured offline using a custom graphical user interface developed in MATLAB (MathWorks, Natick, MA). Each of the images were imported first. While observing the B-mode image, a line was drawn such that it is parallel to the vessel wall. Using the coordinates of the endpoint of the line, the angle with respect to the vertical axis of the image was calculated. The angle was then stored in a text file and only used to calculate the accuracy of the automated algorithm. Figure-\ref{161257} describes the convention used to report Doppler angles in this paper. The value for \(\theta\) ranges from 0 to 180 degrees.