On the Development of a Novel Contrast Pulse Sequence for Polymer-Shelled Microbubbles.

Contrast agents are routinely used in ultrasound examinations. Nonlinear ultrasound imaging techniques have been developed over decades to enhance the contrast between the tissue and the blood pool after the injection of ultrasound contrast agents. In this study, we introduce a new contrast pulse sequence, CPS4. The CPS4 combines pulse inversion, sub-harmonic, and ultra-harmonic techniques to remove propagation distortion while capturing the unique sub-harmonic, and ultra-harmonic responses from ultrasound contrast agents. The novel CPS4 and conventional pulse inversion, sub-harmonic, and ultra-harmonic techniques were used to detect the presence of a research-grade, thick shell, polymer microbubble in a tissue-mimicking flow phantom. The contrast-to-tissue ratio (CTR) obtained from the applications of all techniques were compared. The results show that the highest CTR of approximately 16 dB was obtained using CPS4, which was superior to the individual reference techniques: pulse inversion, sub-harmonic, and ultra-harmonic techniques, at all scenarios considered in this study.