Evaluation of in vivo liver tissue characterization with spectral RF analysis versus elasticity

Ultrasonic elastography, via vibration-controlled transient elastography (VCTE), enables to assess, under active mechanical constraints, the elasticity of the liver, correlating with fibrosis stages. On the other hand, the same VCTE probe can also be used in passive mode, acquiring RF lines at different locations in the liver. This paper presents a thorough evaluation of passive-mode RF spectral parameters (integrated backscatter coefficient, power spectral index, effective scattering size and spectral variance), for tissue characterization on a large cohort of volunteers with various ranges of elasticity measures. Results showed that capabilities to discriminate between liver and subcutaneous fat tissues were highly variable among spectral parameters. Furthermore, it appears that no in vivo discrimination of liver elasticity/fibrosis stage can be performed with passive RF spectral analysis, at 3.5MHz.