Measurement and Numerical Analysis of Acoustic Scattering by Microbubbles Utilizing Phase-inverted Ultrasound Excitation

Contrast-enhanced ultrasound imaging (CEUS) is a commonly used non-invasive technique for cancer detection that utilizes ultrasound contrast agents (UCAs). . However, its low signal-to-noise ratio (SNR) limits detectability in deep tissues and small vessels. To enhance acoustic scattering of UCAs, we have proposed the use of phase-inverted ultrasound excitation and assessed its effectiveness through both experimental and numerical evaluations. The phase-inverted field was generated by dividing the array elements into multiple groups and driving adjacent groups with opposite phases. Scattering coefficients under two-division and three-division driving methods were compared with conventional non-division driving one. In this study, 20 ± 9 μm microbubbles were insonified with a three-cycle burst wave at 1.38 MHz, and scattering was measured as a function of inter-bubble distance (IBD). The results showed that scattering increased as IBD decreased. Among the driving methods, three-division driving method yielded the highest scattering coefficient, exceeding that of non-division driving one by 14% in experiments and 11% in simulations. These findings suggest that multi-division excitation enhances acoustic scattering of microbubbles and may improve CEUS performance in deep tissues and fine vasculature.