Quantitative ultrasonic characterization of diffuse scatterers in the presence of structures that produce coherent echoes

Quantitative ultrasound (QUS) techniques that parameterize the backscattered signal power spectrum have demonstrated significant promise for ultrasonic tissue characterization. Some QUS parameters, including the effective scatterer diameter (ESD) and the effective acoustic concentration (EAC) that can be used for disease detection and diagnosis, require the assumption that the examined medium contains uniform diffuse scatterers. Structures that invalidate this assumption can significantly affect the estimated QUS parameters and decrease performance when classifying disease. In this study, methods were developed to reduce the effects of echoes that invalidate the assumption of uniform diffuse scattering. In order to accomplish this task, backscattered signal sections containing non-diffuse echoes were identified and removed from the QUS analysis. In the first strategy, the data blocks used in the QUS estimation process and that contained non-diffuse echoes were identified and excluded from the QUS characterization of the diffuse scatterers. In the second strategy, power spectra were estimated using a method to reduce or eliminate the effects of non-diffuse echoes on the estimated data block power spectra. QUS analysis was then performed on the modified data block power spectra. Simulations and experiments were used to evaluate the effectiveness of the developed methods. Results indicate that the methods were able to significantly reduce or eliminate the effects of non-diffuse echoes that might exist in the backscattered signal. The methods provide a means to improve the diagnostics of QUS techniques by allowing separate analysis of diffuse and non-diffuse scatterers