Design of apodization profiles using a cystic resolution metric for ultrasound
We have previously described a metric that characterizes the 3D resolution of broadband ultrasound systems [1]. Resolution is expressed as the size of a spherical anechoic cyst, embedded in a speckle generating background, that is required to generate a specific contrast. The contrast of the cyst relative to the background depends on the ratio of the system point spread function (psf) energy outside the cyst to the total psf energy. In this work, we apply our formulation to guide the design of a low-cost, C-scan system being developed at the University of Virginia, demonstrating the utility of our metric in the optimization of system parameters. We simulated the impact of f/# and show that higher f/#'s yield better cystic contrast for larger cysts, but lower contrast for smaller cysts. We also applied a constrained least squares (CLS) approach to design receive apodization profiles to optimize cystic contrast. We use a linear algebra formulation of the psf and minimize the psf's energy in regions outside a specified boundary. We show results that the CLS apodization profiles improve contrast around -10 dB compared to a flat apodization profile at a range of cyst sizes. Our results highlight the metric's utility in designing system parameters and our CLS apodization profiles improve cystic contrast. © 2005 IEEE.
