Ultrasound Medical Imaging: A Novel Super-Resolution Imaging Technique Utilizing Random Interference

Abstract

Medical imaging modalities are used every day in hospitals to examine medical condi-tions, consequently allowing us to analyze anatomical, physiological, metabolic, and functional information of the human body. Ultrasound is one of the most widely used diagnostic tools be-cause it is affordable and non-invasive. Ultrasound is used to assess the tissue, vessels, and or-gans within the human body. In the past few decades, a lot of effort was put by the academic community to improve the quality of ultrasound images. However, despite decades of innova-tion, the main disadvantage of ultrasound is low image resolution. In this dissertation, we develop a novel super-resolution imaging technique utilizing constructive and destructive interference of ultrasonic waves. In particular, we first introduce a method to generate an incident ultrasonic wavefront of random interference. This wavefront then has a spatially variant property that yields individual spatial points, in the region of interest, to reflect mutually incoherent spatial impulse responses. Second, we develop an image recon-struction method based on an L1-norm minimization algorithm that is capable of identifying the scattering points by the presence of spatial impulse responses in the received echo signals. The natural synergy between the properties of the wavefront of random interference and the image reconstruction algorithm allowed us to create the necessary conditions for a successful recon-struction of super-resolution ultrasound images. Lastly, we demonstrate using numerical simula-tions and phantom experiments that the proposed method can achieve four times better spatial resolution. In the simulation study, the proposed method achieved a resolution of 0.25 mm. In the real phantom experiment, we demonstrated that the proposed method can successfully re-construct ultrasound images of nylon wires as small as 0.08 mm in diameter using a tissue-mimicking phantom. We argue that the proposed method is a big step towards achieving super-resolution ultrasound imaging and offers a new perspective on ultrasound imaging. The pro-posed imaging method bypasses the diffraction resolution limit by eliminating the need for the conventional focused ultrasound beam.