Elevational diffraction effect in estimating the local attenuation-coefficient slope using...

Accurate estimation of attenuation coefficient slope (ACS) enhances quantitative ultrasound imaging. We investigate diffraction bias in reference-phantom-free ACS estimation for synthetic transmit aperture (STA) imaging with a one-dimensional linear array. Simulations and experiments show that the elevational focus, rather than the lateral focus, introduces depth-dependent bias: ACS underestimation before focus and overestimation beyond. Applying a Gaussian diffraction correction reduced the ACS error from ±0.28 to ±0.06 dB/cm-MHz in simulations and from ±0.32 to ±0.09 dB/cm-MHz in the experiments. These results indicate that accounting for elevational diffraction reduces bias in reference-phantom-free ACS estimation in STA imaging.