Linear Signal Cancellation of Nonlinear Pulsing Schemes in a Verasonics Research Scanner

Contrast-enhanced ultrasound (CEUS) is a real-time imaging technique that allows the visualization of organ and tumor microcirculation by utilizing the nonlinear response of microbubbles. Nonlinear pulsing schemes are used exclusively in CEUS imaging modes in modern scanners. One important aspect of nonlinear pulsing schemes is the near-complete elimination of the linear signals that originate from tissue. Up until now, no study has investigated the performance of Verasonics scanners in eliminating the linear signals during CEUS and, by extension, the optimal pulsing sequences for performing CEUS. The aim of this article was to investigate linear signal cancellation of the Verasonics scanner performing nonlinear pulsing schemes with two different probes (L7-4 linear array and C5-2 convex array). We have considered two pulsing schemes: pulse inversion (PI) and amplitude modulation (AM). We have also compared our results from the Verasonics scanner with a clinical scanner (Philips iU22). We found that the linear signal cancellation of the transmitted pulse by Verasonics scanner was ~40 dB in AM mode and ~30 dB in PI mode when operated at 0.06 MI. The linear signal cancellation performance of Verasonics scanner was comparable with Philips iU22 scanner in focused AM mode and on average 3 dB better than Philips iU22 scanner in focused PI mode.