Structure function for high-concentration biophantoms of polydisperse scatterer sizes

Abstract

Ultrasonic backscattering coefficient (BSC) has been used extensively to characterize tissue. In most cases, sparse scatterer concentrations are assumed. However, many types of tissues have dense scattering media. This study addresses the problem of dense media scattering by taking into account the correlation among scatterers using the structure functions. The effect of scatterer polydispersity on the structure functions is investigated. Structure function models based on polydisperse scatterers are theoretically developed and experimentally evaluated against the structure functions obtained from cell pellet biophantoms. The biophantoms were constructed by placing live cells of known concentration in coagulation media to form a clot. The BSCs of the biophantoms were estimated using single-element transducers over the frequency range from 11 to 105 MHz. Experimental structure functions were obtained by comparing the BSCs of two cell concentrations. The structure functions predicted by the models agreed with the experimental structure functions. Fitting the models yielded cell radius estimates that were consistent with direct light microscope measures. The results demonstrate the role of scatterer position correlation on dense media scattering, and the significance of scatterer polydispersity on structure functions. This work may lead to more accurate modeling of ultrasonic scattering in dense medium for improved tissue characterization.

High-Frequency Quantitative Ultrasound Spectroscopy of Excised Canine Livers and Mouse Tumors Using the Structure Factor Model

“…This linear relationship has been used to monitor the scatterer radius and/or acoustic concentration. However, the assumption of randomly distributed scatterers may not hold in concentrated cell pellet biophantoms [11] or in tumors with densely packed cells [12]. Therefore, our hypothesis is that a scattering model considering the interference effects caused by the correlations among scatterer positions (i.e.…”

Structure Function Estimated From Histological Tissue Sections

“…Also, the structure function can be affected by the scatterer size distribution. Three Percus-Yevick type structure function models based on different assumptions about the scatterer size and scattering amplitude were discussed in [25]: the monodisperse model, polydisperse model I, and polydisperse model II. The assumptions for the three models are listed in Table 1.…”

“…In this paper, we will develop algorithms for estimating the structure function from the histology of biophantoms and compare the histologically estimated structure function to that estimated acoustically as was done in [25]. 3D histological data have been used by Mamou et al to model and identify scattering structures [40], [41].…”

“…Inspired by the 3DZM approach, this paper investigates the structure function using 2D histological images. Specifically, the aim is to investigate whether the acoustically estimated structure function in [25] was indeed a result of the spatial distribution of scatterers. This investigation is helpful in improving our understanding of the relationship between the backscattered data and histology.…”

“…Section IV will review the structure function results obtained acoustically for the biophantoms in [24], and present the histologically estimated results, and compare the two. The histologically estimated structure function is then compared to a polydisperse structure function model developed in [25]. The structure function results from tumors will also be presented.…”