1. A method comprising: storing in a database at least one continuous wave (CW) Doppler image and at least one characteristic associated with each of the at least one stored Doppler image in a form of an envelope curve; gathering, by a processor, a query Doppler image, and extracting the envelope curve from a velocity profile associated with a query image; matching, by the processor, the at least one characteristic associated with said at least one stored image with at least one characteristic associated with the envelope curve extracted from the query image; and retrieving, by the processor, from the database at least one image having characteristics matching the characteristics associated with the query image.