Global approach for transient shear wave inversion based on the adjoint method: a comprehensive 2D simulation study.

Area of Science:

• Medical imaging
• Biophysics
• Ultrasound technology

Background:

• Shear wave imaging (SWI) uses ultrafast ultrasound to map tissue elasticity.
• Current local inversion methods are sensitive to noise and signal loss.
• Accurate elasticity mapping is crucial for diagnosing conditions like hypoechoic lesions.

Purpose of the Study:

• To evaluate a global approach for elasticity inversion using the adjoint method.
• To compare the global method against traditional local inversion techniques.
• To assess the robustness of the global method in challenging imaging scenarios.

Main Methods:

• Simulated acoustic waveform propagation in a medium with soft and hard lesions.
• Employed a least-squares formulation derived from geophysical full waveform inversion (adjoint method).
• Focused on shear modulus mapping, initially ignoring full elastic propagation and viscosity.

Main Results:

• The global adjoint method demonstrated robust shear modulus map reconstruction, even with non-uniform backgrounds and noise.
• Achieved a contrast increase of approximately +3 dB compared to local inversions.
• Reduced quantification error by approximately +2%.

Conclusions:

• The global adjoint method offers superior performance over local methods for elasticity inversion in SWI.
• This approach is reliable for imaging lesions with no internal signal, improving diagnostic potential.
• The method shows promise for enhanced medical diagnosis through accurate elasticity mapping.