Imaging basic structures using experimental ultrasonic methods coupled with waveform inversion techniques

Abstract

Current diagnostic ultrasound methods focus only on mapping the surface of a pulsing target through an understanding of the times of arrivals of received waveforms. Recent advances in the field of Geophysics, along with increases in computing power, have allowed for the development of full waveform inversion (FWI) techniques that use information about the entire received waveform in order to determine the full internal tomography of an object, mostly geological structures. These methods have not yet been applied to small-scale ultrasound, and the present research sought to apply inversion techniques using ultrasound to image basic structures.

An experimental apparatus was developed in which ultrasound was pulsed and received through a target medium. The data was subsequently sent to be processed in a FWI algorithm. A second apparatus was constructed to determine the impulse response (IR) of transducers for incorporation into inversion algorithms. The research yielded a solid method for IR characterization and resulted in extensive ultrasound imaging data on basic structures which were qualitatively and quantitatively analyzed and that revealed important information about the medium and the target. Together, these two elements of research serve as an experimental proof-of-concept and early venture into small-scale ultrasound methods for determination of full object tomography.