  Non-destructive characterization of multi-layered structures that can be
accessed from only a single side is important for applications such as
well-bore integrity inspection. Existing methods related to Synthetic Aperture
Focusing Technique (SAFT) rapidly produce acceptable results but with
significant artifacts. Recently, ultrasound model-based iterative
reconstruction (UMBIR) approaches have shown significant improvements over
SAFT. However, even these methods produce ringing artifacts due to the high
fractional-bandwidth of the excitation signal.
  In this paper, we propose a ringing artifact reduction method for ultrasound
image reconstruction that uses a multi-agent consensus equilibrium (RARE-MACE)
framework. Our approach integrates a physics-based forward model that accounts
for the propagation of a collimated ultrasonic beam in multi-layered media, a
spatially varying image prior, and a denoiser designed to suppress the ringing
artifacts that are characteristic of reconstructions from high-fractional
bandwidth ultrasound sensor data. We test our method on simulated and
experimental measurements and show substantial improvements in image quality
compared to SAFT and UMBIR.
