Modified X waves with improved field properties.

A method to obtain a good compromise between the depth of field and the lateral resolution of "X waves" is proposed. The original X waves are theoretically nondiffracting beams generated by a specially phased infinite transmit aperture. When generated by a finite aperture, X waves are diffracting beams but have a large depth of field, maintaining uniform lateral field profiles. The proposed modification of the wave equation solution for X waves replaces a constant parameter representing the propagation angle of ultrasound with a function of radial distance at the aperture surface, and results in modified X waves that have a larger depth of field than the original X waves. Computer simulations show that a proper choice of the modification function can produce a new beam with improved field properties compared with the original X waves, promising images with higher lateral resolution and increased contrast over a large depth of field in high frame rate medical imaging. Experimental results are presented to verify the simulation results of the proposed method.