And a time sequence of motion orientation for each block is generated over a sliding time window. Then accumulation and main motion orientation are computed according to the sequence.

The three-step search method is a commonly used fast motion estimation algorithm, but its initial step length is too big, thus the estimation effect of slow motion sequence is not so satisfactory.

An optical flow based approach was presented to estimate coronary arterys two-dimensional motion from a sequence of single-plane angiographic images.