Investigation of Diffraction Factor for A Reference-Phantom-Free Method to Image Particle Size in Synthetic Transmit Aperture Ultrasound Imaging

We investigated the diffraction factor to estimate the form factor of a medium without using a reference phantom. We first developed a method to simulate imaging a scattering medium consisting of objects of finite size in Field II with a one-dimensional array probe in synthetic transmit aperture ultrasound imaging. Then, the diffraction factor of the array probe was estimated in simulations and used to estimate the form factor of the medium and the particle size in simulations.   The aperture of the array probe was divided into multiple overlapping sub-apertures to reduce the spectrum noise of the scattering medium. The diffraction factor was also calculated from the theory and compared with the simulation. The particle sizes estimated by using the diffraction factor from simulations and theory are proportional to the true values. Future studies to improve the proposed method are also discussed.