Analysis and correction of ultrasonic wavefront distortion based on a multilayer phase-screen model

Area of Science:

• Wave Propagation and Imaging
• Biomedical Optics
• Computational Physics

Background:

• Spatial heterogeneities in propagation paths cause cumulative wavefront distortion, degrading imaging system performance.
• Existing aberration-correction techniques often require prior knowledge of the distorting medium, limiting their applicability.

Purpose of the Study:

• To introduce a novel model for incorporating cumulative wavefront distortion effects.
• To present a model-based method for wavefront distortion correction without prior knowledge of the distorting structure.
• To evaluate the proposed method's performance against existing techniques using simulated and experimental data.

Main Methods:

• A distributed heterogeneous medium is modeled as a series of parallel phase screens.
• Wavefront distortion is compensated by backpropagating received wavefronts through hypothetical phase screens.
• Iterative adjustment of pointwise time shifts maximizes a speckle brightness-based image quality factor.

Main Results:

• Theoretical analysis shows mean speckle brightness monotonically decreases with root-mean-square phase distortion, validating its use as an image quality factor.
• Experimental evaluation using 1-D array data with simulated abdominal tissue distortion demonstrated superior performance of the proposed method.
• Simulated distortion characteristics and relative performance of existing methods aligned with previous findings for abdominal and breast tissue.

Conclusions:

• The proposed model-based method effectively compensates for cumulative wavefront distortion in heterogeneous media.
• Speckle brightness serves as a reliable image quality metric for optimizing distortion correction.
• The developed technique offers improved wavefront distortion compensation compared to existing methods.