A methodology for the assessment of cell concentration, in the range 5–100 cells/ $\mu \text{L}$ , suitable for in vivo analysis of serous body fluids is presented in this work. This methodology is based on the quantitative analysis of ultrasound images obtained from cell suspensions and considers applicability criteria, such as short analysis times, moderate frequency, and absolute concentration estimation, all necessary to deal with the variability of tissues among different patients. Numerical simulations provided the framework to analyze the impact of echo overlapping and the polydispersion of scatterer sizes on the cell concentration estimation. The cell concentration range that can be analyzed as a function of the transducer and emitted waveform used was also discussed. Experiments were conducted to evaluate the performance of the method using 7- $\mu \text{m}$ and 12- $\mu \text{m}$ polystyrene particles in water suspensions in the 5–100 particles/ $\mu \text{L}$ range. A single scanning focused transducer working at a central frequency of 20 MHz was used to obtain ultrasound images. The method proposed to estimate the concentration proved to be robust for different particle sizes and variations of gain acquisition settings. The effect of tissues placed in the ultrasound path between the probe and the sample was also investigated using 3-mm-thick tissue mimics. Under this situation, the algorithm was robust for the concentration analysis of 12 $\mu \text{m}$ particle suspensions, yet significant deviations were obtained for the smallest particles.

中文翻译：

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基于细胞回声的超声回声计数评估浆液中细胞极低浓度的新方法

评估细胞浓度（5-100个细胞/个）的方法 $ \ mu \ text {L} $ ，适合 体内这项工作介绍了浆液的分析。该方法基于对从细胞悬液获得的超声图像的定量分析，并考虑了适用标准，例如分析时间短，频率适中和绝对浓度估计，这些都是处理不同患者之间组织变异所必需的。数值模拟为分析回波重叠和散射体大小的多分散对细胞浓度估计的影响提供了框架。还讨论了可以作为换能器和所使用的发射波形的函数进行分析的细胞浓度范围。实验进行了评估，以使用7- $ \ mu \ text {m} $ 和12- $ \ mu \ text {m} $ 水悬浮液中的聚苯乙烯颗粒为5–100颗粒/ $ \ mu \ text {L} $ 范围。使用以20 MHz的中心频率工作的单个扫描聚焦换能器来获取超声图像。所提出的估计浓度的方法被证明对于不同的粒径和增益采集设置的变化是鲁棒的。还使用3毫米厚的组织模拟物研究了放置在探头和样品之间的超声路径中的组织的作用。在这种情况下，该算法对于12种浓度分析的鲁棒性 $ \ mu \ text {m} $ 颗粒悬浮液，但是对于最小的颗粒却获得了明显的偏差。