1. A method of tracking position and velocity of objects' borders in two or three dimensional digital images, particularly in echographic images, comprising the following steps: acquiring a sequence of at least two consecutive ultrasound image frames of a moving tissue or a moving object, said ultrasound image frames being timely separated by a certain time interval; automatically or manually defining a certain number of reference points of a border of said moving tissue or object on a first image frame of said sequence of image frames; automatically tracking said border on at least one frame following said first frame by determining the new position of said reference points by estimating the position of said reference points on the basis of the ultrasound image data of the acquired sequence of image frames, further characterised in that the sequence of image frames acquired is a sequence of consecutive B-mode, grey scale ultrasound images; drawing either manually or by means of an automatic border detection algorithm on a first frame a border line being defined by a trace of pixels of the image frame coinciding with said border line, said trace of pixels coinciding with said manually or automatically drawn border line by searching the maximum likelihood of said trace of pixels in said following image frame with said trace of pixels in said first image frame by analysing the image pixels in the neighbourhood of said trace of pixels.