Estimation of scatterer size from backscattered ultrasound: a simulation study

Abstract

The reliability of the estimation of the size of scattering structures is assessed by realistic simulations and phantom experiments. The acoustic tissue model used in the simulation studies comprised a constant sound speed, homogeneous attenuation, and isotropic scattering. The scattering models considered were a discrete (spherical) model and two inhomogeneous-continuum models. The latter were characterized by an exponential and a Gaussian autocorrelation function, respectively. The backscattering spectra were, over the range from 5 to 10 MHz, fitted to linear, power, and autocorrelation functions of the three scattering models. The effects of the fitting function, the attenuation-either in an intervening layer or within the region of interest (ROI)-of the transmission pulse, and a spread in the scatterer sizes on the accuracy and the precision of the size estimates were assessed. The attenuation in the intervening tissue layer(s) as well as in the ROI itself has a significant effect on the accuracy of the size estimates and needs to be corrected. When performing the attenuation correction the inaccuracy of the attenuation estimate of the intervening layer leads to a large bias in the estimated scatterer size. Experimental results support the conclusion that scatterer size is a feasible tissue characterization parameter.

Precision and accuracy of acoustospectrographic parameters

“…When measuring liver tis sue, a global inhomogeneity, in addition to the local inho mogeneity, is also observed, which is due to the interindi vidual spread of parameter values. An expression for the STD of the attenuation slope (one of the four parameters studied in this article) has been the topic in a number o f articles Kuc 1985;Kuc and Taylor 1982;Parker 1986;Romijn et al 1989). Yao (1991) also analyzed the STD of the backscatter parameters.…”

An in vivo ultrasonic model of liver parenchyma

“…A set of images was simulated [15] according to the basic ultrasonic model described in Section II. The simulated tissue comprised homogeneously distributed point scatterers with on average 10 scatterers within the pulse sampling volume.…”

Evaluation of in vivo Liver Tissue Characterization with Spectral RF Analysis versus Elasticity

“…At 3.5MHz, for an average speed of sound of 1500 m/s in human soft tissues, this corresponds to wavelength λ=430µm, which is of the order of magnitude of the liver microstructures. The spectrogram ) , ( z f S of the RF signal at frequency f and at a distance z from the probe is generally modelled as [3][4]: Regarding the generation of non-specular reflection in a homogeneous tissue, the backscattering spectrum is often modeled as…”

“…The a value providing the theoretical SPI closest to the empirical SPI is then selected as the scatterer size of the observed tissue. In this study we tested two autocorrelation models [4,9], described in Table 1, to estimate the ESS. …”