FIELD: medicine.SUBSTANCE: device comprises an analyzer for reception of electrical signals representing the reflected ultrasonic energy received by each element of the ultrasonic probe, including two-dimensional array of sensor elements, and for signal Doppler power analysis to form a representation of blood flow in a plurality of predetermined locations in the volume and the first flow speed calculation in each location, flow delineating unit in a blood vessel in the sample volume representing the blood flow, angle determination unit to calculate a plurality of points in the delineated bloodstream of the Doppler angle between the beam direction for the emitted collimated beam of ultrasonic energy in each of the plurality of points in the delineated bloodstream, and the direction of blood flow in each of the plurality of points, and Doppler speed calculator to calculate the second blood flow speed in the plurality of points based on the calculated first speeds in the plurality of locations of the calculated Doppler angle. The method for Doppler angle determination to measure the blood flow speed comprises the receiving step, when the electrical signals are received from the two-dimensional array of ultrasonic sensors, the calculation step, when the Doppler power is caluclated within a given frequency band, the formation step, when the first three-dimensional array is formed, the display step, when the second three-dimensional array is formed. Each cell of the second array comprises a binary bit indicating whether the value in the corresponding cell of the first three-dimensional array is above the threshold, identifying adjacent cells which contain binary bits representing values above the threshold, in each two-dimensional array, forming the second three-dimensional array, calculating the three-dimensional coordinates of the center of gravity of area covered by each group in each of the two-dimensional arrays, and calculating the angle between the first line conne
