Backscatter coefficient estimation using tapers with gaps

Abstract

When using the backscatter coefficient (BSC) to estimate quantitative ultrasound (QUS) parameters such as the effective scatterer diameter (ESD) and the effective acoustic concentration (EAC), it is necessary to assume that the interrogated medium contains diffuse scatterers. Structures that invalidate this assumption can significantly affect the estimated BSC parameters in terms of increased bias and variance and decrease performance when classifying disease. In this work, a method was developed to mitigate the effects of non-diffuse echoes, while preserving as much signal as possible for obtaining diffuse scatterer property estimates. Specially designed tapers with gaps that avoid signal truncation were utilized for this purpose. Experiments from physical phantoms were used to evaluate the effectiveness of the proposed BSC estimation methods. The mean squared error (MSE) for BSC between measured and theoretical had an average value of approximately 1.0 and 0.2 when using a Hanning taper and PR taper, respectively, with six gaps. The BSC error due to amplitude bias was smallest for PR tapers with time-bandwidth product Nω = 1. The BSC error due to shape bias was smallest for PR tapers with Nω = 4. These results suggest using different taper types for estimating ESD versus EAC.