Improving accuracy of transverse velocity measurement with a new limited diffraction beam

Limited diffraction beams have a large depth of field and have many potential applications. Previously, the author has applied one of these beams called the Bessel beam to improve the measurement of velocity vector (both transverse and axial components) of flow over conventional focused beams. Here, a new limited diffraction beam called layered array beam is used to further improve the accuracy of the transverse velocity measurement by producing peaks at the boundaries of Doppler spectrum. Because the new beam can be produced with a linear array, the method can be easily incorporated into a commercial scanner. Theory, simulation, and experiment are studied for the method and the results agree excellently with each other. In addition, applications of the new beam for high frame rate imaging (up to 3750 frames/s at 200 mm depth for biological soft tissues) or for dynamic focusing in both transmit and receive without reducing frame rate are discussed.