Optimization of Ultrasound Phase-Encoded Multiplane Wave Tissue Harmonic Imaging

Area of Science:

• Medical imaging
• Ultrasound technology
• Signal processing

Background:

• Tissue harmonic imaging (THI) offers better resolution than conventional imaging but has low signal-to-noise ratio (SNR).
• Phase-encoded excitation can improve THI's SNR, but signal distortion can cause artifacts.
• Optimizing coding schemes and waveforms is crucial for accurate THI.

Purpose of the Study:

• To compare different coding matrices (Hadamard, S-sequence, Golay) and bit waveforms for phase-encoded multiplane wave (MW) tissue harmonic imaging.
• To identify the optimal configuration for maximizing SNR and minimizing artifacts in THI.
• To validate simulation and experimental findings on coding schemes and waveforms.

Main Methods:

• Simulations and experiments were used to analyze coding schemes and bit waveforms.
• Phase-encoded tissue harmonic imaging with multiplane wave transmission was employed.
• Hadamard, S-sequence, and orthogonal Golay coding matrices were evaluated with different bit waveforms.

Main Results:

• Bipolar codes (Hadamard, Golay) were susceptible to phase distortion, causing axial artifacts.
• Hadamard coding avoided artifacts by adjusting plane wave angles, while S-sequence showed no distortion but lower SNR gain.
• Rectangular waveforms improved SNR but caused spectral distortion, especially with Golay, leading to artifacts and reduced contrast.

Conclusions:

• Hadamard coding with a rectangular waveform and selective compounding is optimal for phase-encoded MW tissue harmonic imaging.
• This configuration provides higher SNR than S-sequence and better image quality than orthogonal Golay.
• The findings offer guidance for improving THI performance and diagnostic capabilities.