Improved contrast-enhanced ultrasound imaging with multiplane wave imaging
Contrast-enhanced ultrasound (CEUS) imaging offers great opportunities for new ultrasound applications by improving the contrast between blood and tissue using microbubbles. However, the low signal-to-noise ratio (SNR) due to the low mechanical index (MI) requirement can sometimes be an issue in practice. Multiplane wave (MW) imaging is a technique recently proposed to increase the SNR for compounding plane wave imaging. In this study, we propose to combine CEUS with MW imaging to improve SNR without elevating MI in plane-wave-based CEUS imaging. The MW-CEUS method emits multiple Hadamard-coded CEUS pulses in each transmission events (i.e., pulse-echo events). The received echo signals first undergoes fundamental bandpass filtering (i.e., filter centered on transmit frequency) to eliminate the microbubble 2nd harmonic signals as they cannot be encoded by pulse inversion. The filtered signals are then Hadamard decoded and re-aligned in fast time to recover the signals as they would have been obtained from classic CEUS pulses, followed by designed recombination to cancel the linear tissue responses. The MW-CEUS method significantly improves contrast-to-tissue ratio (CTR) of CEUS imaging by transmitting longer coded pulses with preserved image spatial resolutions. The microbubble disruption ratio in MW-CEUS is also comparable with classic CEUS imaging. In addition, the MW-CEUS sequence can be readily adapted to other transmission coding formats. These properties of MW-CEUS can potentially facilitate CEUS imaging for a wide spectrum of clinical applications, especially for deep abdominal organs or heart.
