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A methodology for the assessment of cell concentration, in the range 5–100 cells/μL, 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-μm and 12-μm polystyrene particles in water suspensions in the 5–100 particles/μL 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 μm particle suspensions, yet significant deviations were obtained for the smallest particles. [ABSTRACT FROM AUTHOR]

Using a generic model of how active array imaging systems operate, a formal definition of the image as a projection of the reflected wave field onto the wave field emitted to probe the medium is proposed. This definition is applied to the case of imaging in homogeneous and isotropic media to which, by using the frequency-domain solution of the wave equation, the relationship between the calculated image, the emitted and received signals, the positions of the transducers, the speed of the waves used, and the reflectivity of the medium is shown at each point. Then, a general algorithm for the formation of images of a region in this kind of media is derived. Finally, using real and simulated ultrasound signals, images obtained with the proposed signal projection method are compared with those produced by the “de facto” standard delay and sum-based algorithms. [ABSTRACT FROM AUTHOR]