Estimation of red blood cell aggregation size using power spectrum considering density of red blood cells in focal region

We have studied a noninvasive and quantitative method for measuring the aggregate size of red blood cells (RBCs). In our previous study, the scattering power spectrum obtained from the vascular lumen was fitted to the reference scattering spectra calculated from the scattering spectrum of a single-sphere scatterer. In this paper, we propose a method for calculating the reference scattering spectra by summing the scattering spectra for numerous scatterers in the ultrasound focal region. By applying this method to the size estimation of microparticles simulating RBC aggregates, the estimated sizes are found to be close to the true values. In in vivo measurements, the estimated sizes at rest are equivalent to the size of a single sphere with the same volume as an RBC, and those during avascularization are larger than those at rest, which is reasonable. The proposed method has the potential to accurately estimate the size of RBC aggregates.