Apparatus and method for estimating a velocity field

A method of determining 2D characteristics of a propagative displacement wave inside a patient, said method comprising:

• estimating a plurality of velocity maps of a target region over time, said estimating phase including the steps consisting in:
• constructing a plurality of echogenicity maps by repeatedly implementing the following sub-steps for each echogenicity map:
• transmitting ultrasounds signals using an array of transducer elements including a group of transducer elements,
• receiving backscattered echo signals by the array of transducer elements, each transducer element allowing the acquisition of a respective temporal signal of a group of temporal signals corresponding to the amplitude of the received backscattered echo signals onto the array of transducer elements,
• constructing the echogenicity map from the group of temporal signals,
• estimating the plurality of velocity maps by correlating and processing the plurality of echogenicity maps,
• filtering the propagative displacement wave within the plurality of velocity maps in order to obtain a filtered plurality of velocity maps,
• determining 2D characteristics including the propagation velocity and the propagation direction of the propagative displacement wave for each point of interest A within the plurality of velocity maps in order to obtain at least one map of 2D characteristics, said point of interest A having the same coordinates within the plurality of velocity maps by:
• associating at least two points B, C within the plurality of velocity maps such that points A, B, C are non-collinear, said points B, C having the same coordinates within the plurality of velocity images/maps,
• extracting a temporal propagative displacement signal from the filtered plurality of velocity maps for each of the three points A, B, C,
• estimating longitudinal and transversal apparent times of flight of the propagative displacement wave between points A, B and C using the temporal propagative displacement signals associated to points A, B, C by:
• intercorrelating the temporal propagative displacement signals associated to points A, B for estimating the longitudinal apparent time of flight of the propagative displacement wave from point A to B,
• intercorrelating the temporal propagative displacement signals associated to points A, C for estimating the transversal apparent time of flight of the propagative displacement wave from point A to C,
• determining propagation direction and propagation velocity of the propagative displacement wave based on the transversal and longitudinal apparent times of flight.