Method of tracking position and velocity of objects' borders in two or three dimensional digital images, particularly in echographic images

A method of tracking position and velocity of object's 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, wherein said 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 of said moving tissue or moving object being defined by a trace of pixels of the image frame coinciding with said border line;
• automatically or manually defining a plurality of reference points along said border line;
• defining transmural cuts for each image frame of said sequence of frames and for each reference point chosen, said transmural cuts defining a line for each reference point which crosses said border line, wherein each one of said transmural cut lines passes through a corresponding one of said plurality of reference points and has a direction substantially orthogonal to said border line;
• placing the pixels taken along each transmural line in each of said image frames of said sequence of image frames in columns, each column of pixels corresponding to the pixels along one of the transmural cuts of one frame of said sequence of images;
• forming a two-dimensional space-time representation of the evolution of the position of each reference point along the corresponding transmural cut, where one axis is the distance along the transmural cut and the other axis is time;
• tracking said border line for each reference point defined on said border line along the corresponding two-dimensional space-time image by using a cross-correlation procedure, wherein said cross-correlation procedure determines the vertical displacement required to maximize the similarity of the pixel column in the space-time image corresponding to image frame N=i with the pixel column in the space-time image corresponding to image frame N=i+1;
• determining the velocity vector for each said reference point along said border line;
• and
• displaying said velocity vector for each said reference point along said border line.