1. A method, comprising: generating a contrast feature curve for a medical image sequence comprising a plurality of frames, wherein the contrast feature curve represents contrast feature values of the frames; detecting a peak in the contrast feature curve; and determining whether the peak corresponds to at least one of contrast injection in an aortic root, contrast injection in a balloon, and a non-contrast injected region; wherein when the contrast feature values of the peak are less than a first threshold and greater than a second threshold, the method further comprises: extracting features from the medical image sequence and feeding the features into a support vector machine (SVM) to train the SVM; and classifying frames in the neighborhood of the peak as being of the contrast injected aorta or not having contrast injection based on the number of neighboring frames classified as contrasted using the SVM.