Bioacoustics Research Laboratory, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 405 North Mathews, Urbana, Illinois 61801, USA.
J Acoust Soc Am. 2011 Dec;130(6):4139-47. doi: 10.1121/1.3655879.
Previous work estimated the ultrasonic backscatter coefficient (BSC) from low-concentration (volume density <3%) Chinese Hamster Ovary (CHO, 6.7-μm cell radius) cell pellets. This study extends the work to higher cell concentrations (volume densities: 9.6% to 63%). At low concentration, BSC magnitude is proportional to the cell concentration and BSC frequency dependency is independent of cell concentration. At high cell concentration, BSC magnitude is not proportional to cell concentration and BSC frequency dependency is dependent on cell concentration. This transition occurs when the volume density reaches between 10% and 30%. Under high cell concentration conditions, the BSC magnitude increases slower than proportionally with the number density at low frequencies (ka<1), as observed by others. However, what is new is that the BSC magnitude can increase either slower or faster than proportionally with number density at high frequencies (ka>1). The concentric sphere model least squares estimates show a decrease in estimated cell radius with number density, suggesting that the concentric spheres model is becoming less applicable as concentration increases because the estimated cell radius becomes smaller than that measured. The critical volume density, starting from when the model becomes less applicable, is estimated to be between 10% and 30% cell volume density.
先前的工作估计了低浓度（体积密度<3%）中国仓鼠卵巢（CHO，6.7μm 细胞半径）细胞团块的超声背散射系数（BSC）。本研究将工作扩展到更高的细胞浓度（体积密度：9.6%至 63%）。在低浓度下，BSC 幅度与细胞浓度成正比，BSC 频率依赖性与细胞浓度无关。在高细胞浓度下，BSC 幅度与细胞浓度不成正比，BSC 频率依赖性与细胞浓度有关。当体积密度达到 10%至 30%之间时，就会发生这种转变。在高细胞浓度条件下，如其他人所观察到的，低频下 BSC 幅度的增加速度慢于与数密度的比例关系（ka<1）。然而，新的是，在高频下（ka>1），BSC 幅度的增加速度可以慢于或快于与数密度的比例关系。同心球模型最小二乘估计显示，随着数密度的增加，估计的细胞半径减小，这表明随着浓度的增加，同心球模型的适用性降低，因为估计的细胞半径变得小于测量的半径。模型适用性降低的起始临界体积密度估计在 10%至 30%的细胞体积密度之间。
