A device of providing a particle flow image comprising the steps of: an ultrasonic array transducer for acquiring ultrasound view frame data by transmitting a series of ultrasonic unfocused M steered plane waves into a structure at a high frame repetition rate in the kHz range, said plane waves being transmitted at transmission angles Tx that change after each wave, thereby providing M number of transmission angles Tx, and receiving waves by said ultrasound array transducer reflected from the structure at different receive steering angles Rx, thereby obtaining N number of receiving angles Rx for each transmission angle Tx; a processing means configured to: for each plane wave emitted perform beam forming of the received waves frame data, over N receive angles Rx, as beam-formed data frames for each transmission angle Tx; wherein at every pixel position in the beam-formed data frames there is a corresponding set of MN, one for each receive and transmission angle pair, slow-time ensembles of beam-formed data having a slow-time sampling rate of said repetition rate; perform multi-level sub-sampling on each of the MN slow-time ensembles to obtain a set of sub-sampled ensembles with finer slow-time resolution; perform on the set of sub-sampled ensembles for all angle pairs: - clutter filtering to suppress tissue echoes; - velocity estimation; and - aliasing correction; average said sub-sampled ensembles for each angle pair to obtain a mean flow estimate vector u; form MN× 2 angle-pair matrix A from all Tx-Rx angle combinations; estimating a flow vector v from a least-square fitting solution of Av = u; and form color-coded arrows based on the flow vector, wherein the color-code and length of the arrow relates to the velocity magnitude at a particular location. an ultrasonic array transducer for acquiring ultrasound view frame data by transmitting a series of ultrasonic unfocused M steered plane waves into a structure at a high frame repetition rate in the kHz range, said plane waves being transmitted at transmission angles Tx that change after each wave, thereby providing M number of transmission angles Tx, and receiving waves by said ultrasound array transducer reflected from the structure at different receive steering angles Rx, thereby obtaining N number of receiving angles Rx for each transmission angle Tx; a processing means configured to: for each plane wave emitted perform beam forming of the received waves frame data, over N receive angles Rx, as beam-formed data frames for each transmission angle Tx; wherein at every pixel position in the beam-formed data frames there is a corresponding set of MN, one for each receive and transmission angle pair, slow-time ensembles of beam-formed data having a slow-time sampling rate of said repetition rate; perform multi-level sub-sampling on each of the MN slow-time ensembles to obtain a set of sub-sampled ensembles with finer slow-time resolution; perform on the set of sub-sampled ensembles for all angle pairs: - clutter filtering to suppress tissue echoes; - velocity estimation; and - aliasing correction; average said sub-sampled ensembles for each angle pair to obtain a mean flow estimate vector u; form MN× 2 angle-pair matrix A from all Tx-Rx angle combinations; estimating a flow vector v from a least-square fitting solution of Av = u; and form color-coded arrows based on the flow vector, wherein the color-code and length of the arrow relates to the velocity magnitude at a particular location. beam forming of the received waves frame data, over N receive angles Rx, as beam-formed data frames for each transmission angle Tx; wherein at every pixel position in the beam-formed data frames there is a corresponding set of MN, one for each receive and transmission angle pair, slow-time ensembles of beam-formed data having a slow-time sampling rate of said repetition rate; perform multi-level sub-sampling on each of the MN slow-time ensembles to obtain a set of sub-sampled ensembles with finer slow-time resolution; perform on the set of sub-sampled ensembles for all angle pairs: - clutter filtering to suppress tissue echoes; - velocity estimation; and - aliasing correction; average - clutter filtering to suppress tissue echoes; - velocity estimation; and - aliasing correction; said sub-sampled ensembles for each angle pair to obtain a mean flow estimate vector u; form MN× 2 angle-pair matrix A from all Tx-Rx angle combinations; estimating a flow vector v from a least-square fitting solution of Av = u; and form color-coded arrows based on the flow vector, wherein the color-code and length of the arrow relates to the velocity magnitude at a particular location.