Simulation of microbubble displacement and normalized singular spectrum area measurements of microbubble signals in a vessel phantom

Targeted ultrasound contrast agents, known as microbubbles (MBs), are used to enhance the utility of diagnostic ultrasound molecular imaging. Previous studies, both in vitro and in vivo, have demonstrated that normalized singular spectrum area (NSSA) can be used to differentiate adherent MB signals from free MB signals as well as from background tissue. We developed a simulation approach to test the hypothesis that the intermediate NSSA values observed in adherent MBs were due to small displacements occurring during exposure to blood flow. We also compared the NSSA mapping result from the simulation with the experimental result. A strong linear correlation between the NSSA values in simulation and experiment suggest that our simulation is reproducing the physical interactions occurring in experimental data and giving rise to the observable NSSA.