Simultaneous evalulation of contrast pulse sequences for ultrafast contrast-enhanced ultrasound imaging

The introduction of programmable platforms with plane wave ultrasound (US) transmissions has enabled implementation of various pulsed waveform types at very high frame rates. This study simultaneously evaluated contrast pulse sequences (CPS) employing different amplitude modulation and pulse inversion (AMPI) US imaging schemes. The overarching objective was to improve the contrast-to-tissue ratio (CTR) during ultrafast contrast-enhanced US (CEUS) imaging. Imaging was performed in vitro in a tissue-mimicking phantom using a Vantage 256 research scanner (Verasonics Inc). After administration, microbubble (MB) contrast agent disruption was minimized at a frame rate of 300 Hz by using a low mechanical index (MI) acoustic output. A set of basis pulses for transducer transmission was implemented and combined post-acquisition to form various AMPI compositions. Comparisons of different CPS was based on CTR measurements relative to conventional B-mode US images. Simultaneous evaluation reduces variability and allows the use of repeated measures for statistical analysis. A 2-fold improvement in CTR of AMPI compared to B-mode US imaging was found with a flexible transducer waveform implementation of three different length AMPI sequences and one AM sequence. These CPS results are applicable to ultrafast plane wave based CEUS imaging. The developed method is also generalizable to the evaluation of other custom US pulsing strategies.