High-Resolution Ultrasound Imaging Using Random Interference

Spatial resolution in conventional sonography is achieved through focusing and steering of an ultrasound beam. However, due to acoustic diffraction, the ability to focus an ultrasound beam is limited which leads to low spatial and contrast resolutions. We aim to propose a new method wherein the array elements are simultaneously excited with signals coded with random sequences, which yields an unfocused ultrasound wavefront of random interference. When such a wavefront propagates through the medium, its energy reflects back from the tissue, causing individual scatterers to have unique impulse responses. In such a case, we can reconstruct high-resolution ultrasound images using a priori measurements of spatial impulse responses and the l₁-norm minimization algorithm. In a simulation study, we achieved a spatial resolution of 0.25 mm, which constitutes a four-fold improvement over conventional methods that use delay-and-sum beamforming. In the experimental study, we demonstrate the accuracy of the proposed interference-based method using a tissue-mimicking phantom with 0.1- and 0.08-mm-diameter nylon wires.