Iterative Sound Speed Tomography for Distributed Aberration Correction

In pulse-echo ultrasound imaging, there exists a strong duality between sound speed estimation and aberration correction. This has led to the development of closed-loop iterative frameworks that address both estimation and correction simultaneously. This work revisits previous work on wave-equation migration velocity analysis (WEMVA) to derive and explain our new closed-loop solution to the problem based on a waveform inversion-style approach: full-waveform iterative model-based phase aberration computed tomography (Full-Waveform IMPACT). Full-Waveform IMPACT reproduces the same velocity-depth ambiguities that many previous works have described. However, by approaching the problem using a waveform inversion-style method, we demonstrate that the velocity-depth ambiguity is intricately tied to the problem of cycle skipping and false local minima.