  Contrast-enhanced ultrasound (CEUS) presents distinct advantages in
diagnostic echography. Utilizing microbubbles (MBs) as conventional contrast
agents enhances vascular visualization and organ perfusion, facilitating
real-time, non-invasive procedures. There is a current tendency to replace the
traditional polydisperse MBs by novel monodisperse formulations in an attempt
to optimize contrast enhancement and guarantee consistent behavior and reliable
imaging outcomes. This study investigates the contrast enhancement achieved by
monodisperse MBs of different sizes, and their influence on nonlinear imaging
artifacts observed in traditional CEUS. To explore the differences between
monodisperse and polydisperse populations without excessive experimentation,
numerical simulations are employed for delivering precise, objective and
expeditious results. The Iterative Nonlinear Contrast Source (INCS) method has
previously demonstrated its efficacy in simulating ultrasound propagation in
large populations in which each bubble has individual properties and several
orders of multiple scattering are significant. Our findings in CEUS imaging
indicate that scattering from resonant monodisperse microbubbles is 11.8 dB
stronger than scattering from the polydisperse population. Furthermore, the
amplitude of nonlinear imaging artifacts downstream of the monodisperse
population is 19.4 dB stronger compared to polydisperse suspension.
Investigating the impact of multiple scattering on polydisperse populations
compared to various monodisperse suspensions reveals that monodisperse MBs are
more effective contrast agents, especially when on resonance. Despite the
strong signal to noise ratio of monodisperse populations, the imaging artifacts
due to nonlinear wave propagation are also enhanced, resulting in more
missclassification of MBs as tissue.
