This work deals with the development of a methodology to evaluate the concentration in cell or particle suspensions from ultrasound images. The novelty of the method is based on two goals: first, it should be valid when the energy reaching the scatterers is unknown and cannot be measured or calibrated. In addition, it should be robust against echo overlap which may occur due to high scatterer concentration. Both characteristics are especially valuable in quantitative ultrasound analysis in the clinical context. In this regard, the present work considers the ability of envelope statistics models to characterize ultrasound images. Envelope statistical analysis are based on the examination of the physical properties of a medium through the study of the statistical distribution of the backscattered signal envelop. A review of the statistical distributions typically used to characterize scattering mediums was conducted. The main parameters of the distribution were estimated from simulations of signals backscattered by particle suspensions. Then, the ability of these parameters to characterize the suspension concentration was analyzed and the µ parameter from the Homodyned-K distribution resulted as the most suitable parameter for the task. Simulations were also used to study the impact of noise, signal amplitude variability and dispersion of particle sizes on the estimation method. The efficiency of the algorithm on experimental measurements was also evaluated. To this end, two sets of ultrasound images were obtained from suspensions of 7 µm and 12 µm polystyrene particles in water, using a 20 MHz focused transducer. The methodology proved to be efficient to quantify the concentration of particle suspensions in the range between 5 and 3000 particles/µl, achieving similar results for both particle sizes and for different signal-to-noise ratios.

这项工作涉及开发一种方法来评估超声图像中细胞或颗粒悬浮液的浓度。该方法的新颖性基于两个目标：首先，当到达散射体的能量未知且无法测量或校准时，它应该是有效的。此外，它应该对由于高散射体浓度而可能发生的回波重叠具有鲁棒性。这两个特征在临床背景下的定量超声分析中特别有价值。在这方面，目前的工作考虑了包络统计模型表征超声图像的能力。包络统计分析基于通过研究反向散射信号包络的统计分布来检查介质的物理特性。对通常用于表征散射介质的统计分布进行了审查。分布的主要参数是通过对由颗粒悬浮液反向散射的信号的模拟来估计的。然后，分析了这些参数表征悬浮液浓度的能力，并且来自 Homodyned-K 分布的μ参数是最适合该任务的参数。还使用模拟来研究噪声、信号幅度可变性和粒度分布对估计方法的影响。还评估了算法对实验测量的效率。为此，使用 20 MHz 聚焦换能器从水中 7 µm 和 12 µm 聚苯乙烯颗粒的悬浮液中获得了两组超声图像。事实证明，该方法可有效量化 5 至 3000 个颗粒/微升范围内的颗粒悬浮液浓度，在两种颗粒尺寸和不同信噪比下获得相似的结果。