Image Quality Degradation from Transmit Delay Profile Quantization

The investigated hypothesis is that quantization of the transmit delay profiles degrades the image quality in plane wave ultrasound imaging. Simulated point spread functions show that transmit delay profile quantization gives rise to artefacts behind the point target. The axial and lateral 6 dB resolution is unaffected, but contrast is reduced. This is quantified by a 20 dB cystic resolution of 1.23 mm compared to 0.53 mm for the ideal (non-quantized) case at 10 mm depth. It is also shown that providing individually phase-shifted excitation waveforms to each element restores the image quality, as seen by the 20 dB cystic resolution being restored to 0.53 mm. The impact on high-quality imaging is discussed.