Ultrasonic backscatter coefficient quantitative estimates from Chinese hamster ovary cell pellet biophantoms

Abstract

A cell pellet biophantom technique is introduced, and applied to the ultrasonic backscatter coefficient (BSC) estimate using Chinese hamster ovary (CHO) cells. Also introduced is a concentric sphere scattering model because of its geometrical similarities to cells with a nucleus. BSC comparisons were made between the concentric sphere model and other well-understood models for mathematical verification purposes. BSC estimates from CHO cell pellet biophantoms of known number density were performed with 40 and 80 MHz focused transducers (overall bandwidth: 26-105 MHz). These biophantoms were histologically processed and then evaluated for cell viability. Cell pellet BSC estimates were in agreement with the concentric sphere model. Fitting the model to the BSC data yielded quantitative values for the outer sphere and inner sphere. The radius of the cell model was 6.8 ± 0.7 μm; the impedance of the cytoplasm model was 1.63 ± 0.03 Mrayl and the impedance of the nuclear model was 1.55 ± 0.09 Mrayl. The concentric sphere model appears as a new tool for providing quantitative information on cell structures and will tend to have a fundamental role in the classification of biological tissues.

Experimental Application of Ultrafast Imaging to Spectral Tissue Characterization

“…For most scattering tissues, the BSC presents an intrinsic stochastic behavior as it depends on the random position of scatterers (Insana and Brown 1993;Insana et al 1990;Teisseire et al 2010) or, for spatially correlated scatterers, on the pair-correlation function describing the relative position of their structures, which is also a random process (Fontaine et al 1999;Franceschini and Cloutier 2013;Saha and Kolios 2011;Sav ery and Cloutier 2001). Likewise, the measurement of BSC is affected by electronic noise, which is also stochastic by nature.…”

On the use of the Structure Factor Model to understand the measured backscatter coefficient from concentrated cell pellet biophantoms

“…The preparation of the cell pellet biophantoms was adapted from Teisseire et al [7] and is presented here. Human leukemia K562 cells were obtained from the European Collection of Cell Cultures (Salisbury, UK).…”

“…The biophantoms had identical cells but had different cell volume fractions ranging from 0.03 to 0.3. As originally proposed in [7], [8], the cell pellet biophantoms are a simplified version of real tissues since only a single cell line is considered. The concentrated biophantoms allow to mimic densely packed cells with controlled cell volume fractions.…”

The measurement of ultrasound backscattering from cell pellet biophantoms and tumors ex vivo

“…Two scattering models were evaluated against the BSC results: the fluid-filled sphere model and the concentric spheres model (Teisseire et al, 2010;Fig. 2).…”

“…However, a statistical model was used that assumed point scatterers and the study did not deal with anatomic structure of groupings of cells. Teisseire et al (2010) constructed cell pellet biophantoms that were composed of cells embedded in a plasma-thrombin supportive background and proposed an anatomy-matching model-the concentric spheres scattering model-wherein a eukaryotic cell was modeled as concentric fluid spheres, with the inner sphere and outer shell modeling the cell nucleus and cytoplasm, respectively. The backscatter coefficient (BSC) estimates from the biophantoms were shown to agree with the two concentric fluid spheres theory (McNew et al, 2009) for relatively low cell concentrations (cell volume fraction <3%).…”