Measuring the Absolute Concentration of Microparticles in Suspension Using High-Frequency B-Mode Ultrasound Imaging

Concentration measurement of particles in suspension is an important procedure performed in biological and clinical laboratories. Existing methods based on instruments such as hemocytometers, Coulter counters and flow cytometers are often laborious, destructive and incapable of in vivo measurements. On the other hand, an ultrasound-based method can be non-destructive and non-invasive and have the potential for in vivo measurement. In this work, a method is presented that estimates absolute particle concentration from high-frequency B-mode ultrasound images of a sample. The method is based on the detection and characterization of the echoes from individual particles to estimate the effective slice thickness of the image. Calibration using a reference sample is not required because the estimation is entirely image based. The particle type differential is also performed by using the backscatter coefficient of each detected echoes. The method is demonstrated by measuring microsphere suspensions as well as human T-cell suspensions. The proposed method has a wide range of potential clinical applications including non-invasive measurement of cell concentration in biological fluids such as cerebrospinal fluid.