Abstract
This study introduces a proof-of-concept methodology for evaluating pressure-dependent non-linear acoustic properties of liver tissue. The proposed non-linearity index (NLI) is derived from echo amplitudes obtained at two substantially different acoustic pressures. Unlike previous harmonic-based approaches, the method relies solely on the fundamental frequency band, allowing clinical implementation without additional system modifications. The NLI is estimated as a ratio of local amplitudes of the amplified low-pressure image (ALPI) to the high-pressure image (HPI). Experimental validation includes hydrophone measurements, k-Wave simulations, and in vivo imaging of healthy and fatty livers. The results demonstrate that NLI values increase with the degree of steatosis, in agreement with theoretical expectations based on tissue B/A coefficients.
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